Choosing the correct White Plastisol Ink
With so many white inks to choose from on the market today, it can become very confusing and frustrating when trying to choose the correct white plastisol to use as an under base for flash curing applications. Is there a “miracle white” that does it all or is it necessary for printers to inventory more than one white ink?
* What is Underbasing?
Underbasing is a process where a white ink is printed on a dark colored shirt, placed underneath a drying unit called a flash cure dryer which brings the ink film to a minimum gel temperature and allows colors to be printed on top of the white under base ink. Because this process basically turns the substrate you are printing on from a dark color to a white, it allows you to produce vibrant prints while utilizing medium opacity inks such as QCM’s WOW Series (Wet on Wet) Series of inks, Metallics and QMX Fluorescents.
* What QCM Inks Are The Best Choices For 100% Cotton Dark Shirts?
The best choice for underbasing 100% cotton dark shirts is XOLB-102 Cotton White or WOW-101 White. Its creamy, easy-printing consistency allows it to be printed through fine mesh counts to achieve soft hand prints. XOLB-102 Cotton White and WOW-101 provides a smooth surface for overprint colors and is formulated to be a purer white color in appearance. XOLB-102 Cotton White has no after flash tack which is important if you cannot afford to sacrifice a print head as a cool down station (see section titled “Printing Parameters” for more information about cool down stations). If a printer wants to have one ink for an underbase, highlight white or standard white ink for 100% cotton XOLB-102 Cotton White or WOW-101 are the best choices.
Up to this point, we have only discussed printing on 100% cotton fabric. QCM Ink does not recommend the use of Low-Bleed white inks on 100% cotton. There are several reasons. The most important reason is that low-bleed inks can cause a condition known as “ghosting” on some colors of cotton. Ghosting occurs most often when a sensitive color of garment is printed and then stacked or folded when still warm. The anti-bleed ingredients in the low-bleed white then continue to outgas and can cause the dye of the garment above to fade and create a ghost image. This phenomenon can occur with all brands of low-bleed ink. QCM Ink places a warning about this phenomenon on the label of all of our low-bleed inks.
* What Inks Are The Best Choices For Polyester or Polyester Blend Garments?
Because shirts containing any amounts of polyester are prone to dye migration (bleeding) specially formulated ink must be used on this substrate. This ink is manufactured with special ingredients to prevent the dyes of the shirt from migrating through the ink film.
Many printers successfully use the PERM 170 White as an underbase white through 160 and higher mesh count screens. The superior bleed resistant of PERM 170 also helps blocks dye migration as long as the entire ink film reaches 300 degrees Fahrenheit during the curing process.
* Mesh Specifications For Underbase Whites*
PERM 170 WHITE
(listed in threads/inch, for metric sizes, divide by 2.54)
Simple block areas: 160-180 (Manual Press) 200-230 (Automatic Press).
Detailed images: 160-230 (Manual Press) 230 (Automatic Press).
Fine line halftones: 200-230 (Manual Press) 230-305 (Automatic Press).
* Mesh Specification For Overprint Colors*
Simple block areas: 200 (Manual Press) 260 (Automatic Press).
Detailed images: 230 (Manual Press) 305 (Automatic Press).
Fine line halftones: 260 (Manual Press) 350 (Automatic Press).
*These are guidelines only and may need to be varied depending upon the amount of detail and the number of colors in the design
* Printing Specifications
Underbase screens on your automatic or manual press should be set off-contact in order for the ink to clear the screen cleanly. A screen set at the proper off-contact (0.040″ to 0.100″) and with good screen tension (25 newtons or greater) works best. With improperly tensions screens or too much off-contact, it may be necessary to double stroke the underbase to clear the ink from the screen cleanly and provide the smoothest surface for the overprint colors.
Squeegees should be set at a slight angle and with just enough pressure applied to clear the ink from the screen. It is recommended printers using automatic presses back off the squeegee pressure until the ink does not print and then slowly increase the pressure until the desired underbase print is achieved. Remember, you are trying to print the ink on top of the garment, not drive the ink through the garment. If the print starts appearing on your platen you are probably using too much pressure.
If possible, overprint colors should be printed from the smallest to largest area of coverage in order to minimize pick-up on the backs of the screens. Squeegee pressure is important in this stage because you are now printing on a piece of non-absorbent vinyl that is not as forgiving as an absorbent garment. Too much pressure will cause the colors to smear. To alleviate this problem either use a lighter pressure during the print stroke or utilize finer mesh counts for overprint colors.
* Flash Curing the Underbase
Your flash cure unit must be large enough to not only cover the design but should be at least 4″ larger than the design you are flash curing. Some of the smaller 16 inch square units can barely cure a 14 inch design much less the oversized prints in demand by customers today.
The flash cure unit should be positioned above the design so you can get a partially cured print in a matter of 3-5 seconds while not burning the garment. Plastisols will reach what is called the gel temperature at approximately 240 degrees Fahrenheit. The temperature can be measured with either a temperature strip or temperature probe available from NB GARBER INC. Caution: Be careful not to fully cure the underbase ink. An overprint color may not adhere to a fully cured underbase and flake off after the shirt is washed. Another indication of over curing the underbase is if little pinholes of white can be seen through the overprint color. If so, lower your flash cure temperature or raise the height of the flash cure unit.
After flash curing the underbase white, the ink may be appear sticky even though it is fully gelled. This phenomenon is known as “after-flash tack” and usually occurs in inks not specifically formulated for flash curing. It occurs more frequently on automatic presses because of the production speeds. This tack goes away in a few seconds but slows down production in the meantime.
To eliminate this problem a cool down station may be necessary or fans may be needed between print heads to cool down the underbase print. For example, on a six color press the underbase would be printed on head #1, flash cured on head #2, head #3 would be empty and used as the cool down station. The overprint colors would be printed on heads #4, #5, and 6. Because of the cool down station you will be limited to three colors. This is why the best choice is to use ink specifically designed for underbasing where after flash tack is not a factor.
On manual presses with rotary table platens “after flash tack” is usually not a factor because the underbase has had sufficient time to cool and lose the “after flash tack” before the print comes back around for the overprint colors.
Customer testing is required and should be mandatory with this product or any new product or process before running production. Our technical advice and recommendations given verbally, in writing, or by trials are believed to be correct. They are not binding also with regard to the possible rights of third parties and do not exempt you from your task of examining the suitability of our products for the intended use. We cannot accept any responsibility for application and processing methods that are beyond our control, nor can we accept responsibility for misuse by you of the products or use by you of the products outside the specified written instructions given with the products. User must protect sensitive skin, exposed wounds and eyes from contact with products.
QCM Discharge Snow White
No other process produces such soft, breathable, absorbent, bright prints on dark colored garments. Also, no other process has been as misunderstood and maligned as discharge printing. This paper honestly addresses the health and safety non issues of Zinc Formaldehyde Sulfoxylate (ZFS) based discharge inks and points out the overwhelming advantages of the process. This article will also instruct you on how to print bright, opaque colors using the Discharge Snow White as your underbase white for overprinting plastisol inks on dark garments.
What is Discharging?
Discharging is a chemical reaction that destroys the ability of selected dyes to reflect color. This reaction takes place at temperatures above 180 degrees Fahrenheit while water is present.
What Shirts Are Dischargeable?
Only selected dyes used on natural fibers are dischargeable. Fruit of the Loom and Lee are the only major garment manufacturers stating some colors of their 100% cotton T shirts will discharge well. Fruit of the Loom rates their black, navy, denim, burgundy and brick as being the most dischargeable and their wedgewood, cadet blue, royal, purple and yellowjacket as the poorest. Other colors fall somewhere between.
Lee rates their shirts on a 1-10 scale with ten being the most dischargeable. Lee colors rated as tens are: black, gold, navy, purple, english rose, primrose and powder blue. Colors rated at 7 and discharging ok are peacock, kelly, wine and true red. Colors rated as poorest dischargeable colors are royal, hunter and ash.
Printers are advised to test the dye lot of each new case of shirts by checking the dischargeability of the top and bottom garment in the area to be printed or on an inner seam and put aside undischargeable garments to other uses.
What Are The Advantages Of Using A Discharge Underbase Over a Normal Plastisol Underbase?
The discharge underbase will produce a softer feeling print which will not have the rubbery feel associated with a dark garment printed with a regular white plastisol underbase. The printer will also increase his production output because the absorbency of the discharge underbase into the shirt allows the printer to print each subsequent color on top of the discharge underbase wet on wet. To eliminate pick-up on screens overprinted onto the discharge underbase printers may elect to flash cure the underbase print for about 1 second. However, if printers decide to flash cure it negates part of the increased production advantages of this process.
Why Use A Plastisol Discharge Mixture Over A Waterbase Discharge?
Most textile printers are comfortable with plastisols and are familiar with the techniques of how to use them. Although a 100% waterbase discharge print yields the ultimate in softness, breathability and absorbency, prints produced by overprinting QCM plastisols wet on wet through fine meshes over a plastisol discharge underbase come very close without the problems of drying in the screen and the pot life associated with straight waterbase discharge inks.
Mixing of Snow White Discharge and ZFS Powder
Discharge Snow White is a two part system and will not work without the addition of the ZFS powder. It is recommended printers add 6% by weight of the powder to the Discharge White and mix until completely dispersed. Even though the Discharge White has a shelf life of 6 months, it is advised printers only mix the amount of final product which can be used in a 24 hour period.
Water resistant stencils are required for both the underbase screen and each subsequent screen.
Recommended mesh size for the underbase screen is a 156T monofilament polyester. Overprint colors such as the XOLB or WOW Series may be printed through mesh sizes ranging from 156T-350T monofilament polyester.
Printing the discharge underbase is directly opposite that of printing a regular plastisol underbase. Adjust your technique so the ink is driven into the fabric deep enough to destroy the garment color beyond visible depth and to avoid having undischarged sides of individual threads showing when the fabric is stretched. This is usually achieved with extra heavy squeegee pressure and a fast squeegee stroke. Plastisols may then be printed wet on wet on top of the discharge underbase. Printers have successfully flash cured the Discharge White for 1 second in order to eliminate picking up of the underbase on the subsequent screens.
Curing of Print
A minimum of 90 seconds in a well ventilated oven where the entire ink film temperature reaches 320 degrees Fahrenheit is required to perform the discharge process and at the same time cure the overprint plastisols. Caution: This is a critical phase of the discharge process. If your oven does not allow the garment to remain in the heat chamber for at least 90 seconds it could effect the results of the finished print.
Environmental Concerns Regarding ZFS
The following excerpt is directly from a federal EPA letter concerning zinc formaldehyde sulfoxylate which is the discharge agent used in DSPCH-1000.
“A review of the current office of water activities reveals that there are no current regulations specifically controlling zink formaldehyde sulfoxylate (ZFS). Also according to the Office of Pesticides and Toxic Substances Hot Line, which has a computer based Federal Register (FR) data base, there have not been any FR notices/publications over the past ten years discussing, proposing, or promulgating rules for ZFS. Further, we are not aware of any situation where state or local officials have established controls for ZFS or banned the release of ZFS into water..”
As the above excerpt from the letter is dated June 11, 1991, the Toxic Substance Hot Line and Federal EPA have been asked to keep us advised of any changes in the status of ZFS and we will call them to check every few months. If anyone wants to check the accuracy of the above statement and to make sure there has been no change for themselves, the telephone numbers are:
Federal EPA- 1-202-260-7120 Toxic Substance Hot Line- 1-202-554-1404
Giving the CASE# for ZFS (24887-06-7) along with the name (ZFS) will expedite matters. Even though there are no specific laws against putting ZFS into water it should not be taken as an invitation to dump it down a drain. All chemicals should be disposed of as specified by local laws and your MSDS.
Health and Safety Concerns Regarding ZFS
According to the Material Safety Data Sheets for ZFS, qualified experts and results of actual monitoring; formaldehyde in ZFS is not set free prior to, during or after the discharge reaction. Even if it is was set free it should combine with a scavenger built into all UNION discharge bases.
Possible products of decomposition include carbon monoxide, carbon dioxide, sulfur dioxide and zinc oxides. PEL and TLF for sulfur dioxide is 2ppm in any eight period (5ppm STEL). Sulfur dioxide can cause irritation of the respiratory tract. PEL and TVL for zinc oxide is 5 Mg/m to the third power in any eight hour period. Zinc oxides could theoretically cause metal fume fever. PEL is the abbreviation for Permissible Exposure Limit. TVL is the abbreviation for Threshhold Limit Value which is the maximum level recommended for a lifetime of exposure for 8 hours per day. STEL is the abbreviation for Short Term Limit Exposure which means maximum level recommended even for brief exposure.
Any fumes generated in a well ventilated oven should pose no problems. Adequate ventilation recommended for any shop area should be sufficient enough for a good air exchange rate. Air blowing directly on the screens should be avoided as this will cause the inks to dry in the screen.
QCM Discharge Snow White is solvent free and made with the safest possible ingredients. However, prolonged contact could cause skin irritation in sensitive individuals especially after the ZFS is added. Additionally, dried prints contain chemicals that could irritate the skin of sensitive individuals if the garment is worn prior to washing. Prolonged contact with the ink or unwashed prints should be avoided.
Clean-up Of The Discharge Underbase Screen
Simply use a sponge or rag saturated with clean water and wipe out the screen and image area until completely clean. Follow the same procedure for any other screen in the design Which may have picked up any of the underbase print on the print side of the screen.
Customer testing is required and should be mandatory with this product or any new product or process before running production. Our technical advice and recommendations given verbally, in writing, or by trials are believed to be correct. They are not binding also with regard to the possible rights of third parties and do not exempt you from your task of examining the suitability of our products for the intended use. We cannot accept any responsibility for application and processing methods which are beyond our control, nor can we accept responsibility for misuse by you of the products or use by you of the products outside the specified written instructions given with the products. User must protect sensitive skin, exposed wounds and eyes from contact with products.
Evaluating Plastisol Curing
The staff of Union Ink Company fields hundreds of questions annually about the use of their printing inks. Questions like “Why is my design cracking?” and “Why is the ink coming off after washing?” make up the majority of problems screen printers encounter. In this paper we are going to describe why the design cracks or washes off the garment, the stages the ink and garment go through during the curing process as well as what you can do to ensure the garments you deliver to your customers are cured.
What is plastisol ink?
Plastisol inks are simple compounds mainly made up of PVC (polyvinyl chloride) resin, plasticizers and pigments. Other components such as fillers which may be used for opacity, modifiers which may be used to adjust viscosity or components to give an ink its low-bleed characteristics may be added to the ink by the manufacturer depending upon the particular application for the ink. Plastisol inks do not air dry and only through the introduction of heat do they become solid and washfast.
What are the stages a plastisol ink goes through during the curing process?
A plastisol ink goes through three stages. The first stage is the wet stage which is the state of a plastiol ink in the container or just after it has been printed on the garment prior to putting it through the dryer. The second stage is the gel stage which occurs somewhere between 180°—250°F depending upon the type of plastisol. The gel stage is the state you are trying to reach with a flash-cured underbase or conveyor-cured transfer, dry to the touch on the surface but not fully cured. The third and final stage is the cure stage. The final cure occurs when the entire ink film from top to bottom reaches 280°—320°F. and again depends upon the type of plastisol. Even though the vast majority of Union plastisols cure at 300° F., some special effects inks such as Hi-Square, Flash-Black, Shimmer, Suede or Glitter have higher recommended curing temperatures. Always consult the Union Ink Technical Data Sheet to detemine the cure temperature for the ink you are printing prior to any production run.
Are there differences in testing direct printed garments and transfers for gel and cure?
Yes, there is a major difference between the desired cure of a direct print on a garment and the desired cure on a plastisol transfer. While most people believe you cannot overcure a direct print (except an underbase), overcuring a transfer may result in difficult or faulty application of the later transfer of the print to a garment. Inks on a transfer should only be partially cured (gelled) to the extent that they can be stacked, cut, packaged and shipped without sticking together. The full cure of the plastisol occurs later at the time of transfer.
Temperature measuring devices do not apply here. Standard procedure is to decrease conveyor heat until you observe some ink set-off on the backs of the sheets at the delivery end and then raise the temperature or lower the conveyor speed until the set-off disappears.
How does a plastisol ink cure?
How a plastisol ink cures is another very simple process. Remember the PVC resins we spoke of earlier? Once these PVC resins used in the ink are exposed to heat, they begin to swell and react like small sponges to absorb the plasticizer. When all the plasticizer in the ink is absorbed by the resins you have a flexible, solid film called an “elastomer” which is tightly bound to the garment and washfast.
Are there other variables besides ink to consider?
Yes,there are many other considerations when curing a garment printed with plastiol ink.
• The Fabric
Many printers think that heat is heat and the ink will cure at the exact same dryer temperature setting and belt speed for all garments. Many printers have also discovered this is a myth after undercuring garments and having to reprint the job. Fabric content will determine the length of time it takes to evaporate the moisture from the garments. Garments made from 100% cotton take longer because cotton fibers absorb and hold moisture unlike fibers of polyester or nylon.
Fabric color must also be considered. The same reason you don’t want to wear a black t-shirt to the beach on the hottest summer day is the same reason dark colored garments cure quicker. Dark fabrics absorb heat instead of reflecting and will come up to temperature at a faster rate than light colored fabrics.
The weight of the garment is another factor to consider in the curing process. Are you printing t-shirts, four-ply nylon reversible basketball jerseys, football jerseys or pants, sweatshirts or cut pieces that are printed prior to being sewn into a finished garment. All of these garments are of different thicknesses and the curing time for the garments will be different. The thicker the fabric the longer it takes to bring the fabric under the print up to temperature. Again, remember the moisture content we spoke of earlier. The heavyweight 100% cotton t-shirts not only take longer to bring up to temperature due to the fabric thickness but also have more surface area in which to hold in moisture which has to be evaporated before you can bring the heavier fabric under the print up to temperature.
• Ink Film Thickness And Type of Ink
Different ink film thicknesses cure differently for the same reason different fabric thicknesses cure differently. There is more volume to be brought up to temperature. Even though the recommended cure temperature is 300° F for both inks, the thick athletic uniform print requires more time and heat than a soft hand print on a white t-shirt. Glitter or shimmer inks require more time and temperature but for a different reason. The metallic characteristics of these inks tend to reflect infra-red heat and require a longer time in the dryer as well as more heat to reach their required curing temperatures.
• Room Temperature
One variable that often gets overlooked is what I refer to as the Spring/Fall Syndrome. Spring and Fall is the time of year I receive the most complaints about ink performance resulting from undercure. In the South, it is often too nice to have the the heat on in early Spring but not yet hot enough to use the air conditioning. Likewise, in the Fall , it is not warm enough to justify using the air conditioning and not cool enough to need the heat. During these two periods I have seen many print shops open the doors and windows to enjoy the fresh air and also let Mother Nature provide the climate control for the shop. Having the doors and windows open creates a draft that sucks heat from your dryer and out the open windows or doors. The printed garment now has to compete with the outside elements to receive enough heat to become fully cured. This is the same principle that happens when our children’s friends come over in January and have a full conversation at the front door with one child inside and the other standing outside while all the heat rushes out the door.
How do I measure ink film temperature?
Most shops measure their ink film temperature with either a donut probe, temperature tapes or a non-contact infra-red thermometer. However, these methods only provide a reference for setting dryer temperatures and should not be used as a final test for determining cure. There are marked differences of opinion throughout the industry as to which of these types is most effective in helping the screen printer set his equipment temperatures most accurately.
• Temperature Tapes— Pressure sensitive pieces of tape that are placed next to the print. One model has a coating with one temperature (270° F.) that is grey in appearance at room temperature but turns black and stays black when the temperature reaches that particular level. The second type has five fixed temperature levels on each tape. These five levels come in temperature ranges of 240—280°, 290—330° F., and 340—380° F. and also blacken and stay black when the temperature reaches that level. Even though many say these tapes are inaccurate because they only measure the temperature of the tape and not the ink film they are still commonly used due to their low cost. However, it is difficult to dispute chemists and printers who say that the technique of placing the temperature tape inside the garment underneath the ink area is the only way you can prove the entire ink film above the tape has reached the required temperature. Many industry experts suspect the accuracy of these tapes to be somewhere around + or – 10% so you must be careful that an indication of 330° F. is not actually 10 percent less or closer to 297° F. where the ink film may not fully cure.
• Donut Probe—A round, teflon ring with two wires that cross in the center of the ring. The ring is connected to a hand-held thermometer by a teflon coated wire. The donut is placed on the print with the two wires actually sitting in the wet ink. As the garment travels though the dryer the actual ink film temperature appears on the screen of the hand held thermometer. This is considered to be a very accurate measurement of ink film temperature because you are seeing the temperature deeply into the as the wires sink through the ink and touch the garment. However, the accuracy of this method has also proven to be somewhat suspect depending upon the length of the dryer and by how well shops keep the contact point (where the wires cross) free of oil and ink residue to prevent false readings.
• Non-Contact Infra-Red Thermometer (sometimes called a raygun because of the manufacturers name)—These devices are hand-held and when aimed at the print from a distance of 6-12 inches provide a good reference point for the temperature of your ink film. Like the previous two methods the non-contact thermometer is not without a disclaimer also. It only measures the surface temperature of the ink film and does not tell you the temperature in the middle of the ink film or at the bottom where the ink film actually touches the shirt. You must make sure you are aiming accurately at the printed design. Even with these disclaimers, there are many who claim that its speed and accuracy make it the current way to go.
What is the best way to determine if my garments are fully cured?
While all the temperature measuring devices described above work well, they should only be used to provide a good reference point setting dryer settings. The definitive test to determine a fully cured print is still by washing the printed garment a minimum of three times. To perform this test use two garments that have been printed during a full production run. Do not use a shirt that has been printed and put through the oven by itself. Instead use a fully loaded belt to simulate a production situation. Unlike a conveyor belt loaded with multiple garments, a single garment requires less energy to cure because it does not have to share the heat with other garments. Turn one shirt inside out and leave the other garment right side out and wash with at least 5 pounds of other laundry to simulate the exact conditions in which your customer will launder the garment. One printer I know cuts the design in half and places it inside another t-shirt to simulate turning the shirt inside out. After each cycle he compares the washed printed with the unwashed print to detect any differences in the prints. While this method is time consuming, it is the only true test of whether the printed ink is fully cured and meets the requirements of the ultimate user. There are those who are proponents of a chemical test or stretching the garment to observe relative ink cracking, but the garment wearer is more interested in whether or not the print fails when washed than if it withstands ethyl acetate, etc.
Can overcuring and overflashing become a problem when printing plastisol inks?
Yes, if you are printing on polyester/cotton blended or 100% polyester garments too much heat can cause the dyes in the garment to migrate through the ink film. Just as undercuring the ink film can cause the dyes to sublimate and migrate through the ink film turning the white ink printed on the red garment pink, too much heat can produce the same result. One major uniform manufacturer in the Southeast recommends that the temperature of their 100% polyester uniforms not exceed 330° F. Even though the ink film is fully cured the components used to give the inks their low-bleed characteristics do not stand a chance if too much heat is applied to the garment. As one of our technical representatives says “Remember these inks are low-bleed, not no bleed”. When printing any polyester blended garment you will not only have to ensure a full cure but also ensure that you do not overcure.
Overflashing can cause a problem with the adhesion of the top colors adhering to the underbase color. If for some reason a printer would actually cure the underbase print he would get what is called poor “intercoat adhesion” of the top colors to the underbase colors. Recommended gel or flash cure temperatures of inks commonly used to underbase are approximately 240—250°
If the entire print looks faded, is this undercure?
More than likely if the entire print is faded evenly you are seeing a phenomena call fibrillation. Simply speaking fibrillation is caused when shirt fibers raise up through the print because there is not enough ink on the shirt to hold down the fibers. Fibrillation mainly occurs on white or light colored garments made from 100% cotton where the design has been printed with fine mesh counts to produce a soft print. It is also common on four color process prints for the same reasons. It is not seen on dark colored garments because the thicker ink deposits printed to cover the dark background hold down the fibers.
A simple test to determine whether you have fibrillation or undercure is to wet your thumb and rub it across the print and observe to see if the deeper color returns. You can also look at the shirt immediately after it is washed because the wetness of the wash cycle will bring back the color. Fibrillation can be corrected by utilizing coarser mesh counts to print a thicker ink deposit or by flash-curing and making an extra screen that allows you to overprint the entire design Mixopake (MIXO-9070) Soft Hand Transparent Base to hold down the fibers.
For more information
This paper was written and produced for your information by the staff of Union Ink Company. For more information about this product, process or any other Union Ink product please call 1-800-526-0455. You may also receive technical information via the World Wide Web at www.unionink.com or by e-mailing your request to firstname.lastname@example.org.
Customer testing is required and should be mandatory with this product or any new product or process before beginning production. Our technical advice and recommendations given verbally, in writing, or by trials are believed to be correct. There are certain personal opinions expressed above which should be evaluated by the printer in his/her own environment and circumstances. They are not binding also with regard to the possible rights of third parties and do not exempt you from your task of examining the suitability of our products for the intended use. We cannot accept any responsibility for application and processing methods which are beyond our control, nor can we accept responsibility for misuse by you of the products or use by you of the products outside the specified written instructions given with the products.
Union Ink Company will replace or refund any defective product returned to us within 1 year of the date of purchase. This warranty is in lieu of any implied warranty of merchantability or fitness, and no other warranty shall apply. The user is responsible to determine whether the product is suitable for each particular substrate and application. The user must test thoroughly (including wash and storage tests) before using in production. In no event will Union Ink Company be responsible for indirect or consequential damages such as damaged substrates or printing labor.
Printing Nylon and Polyester Athletic Uniforms
Anyone who has ever direct printed 100% nylon or 100% polyester athletic uniforms readily admits to the challenges faced in completing the job correctly. Many printers have even resorted to thermoplastic die-cut numerals, transferring the numbers to the uniforms leaving only the team name and logo to the direct printing process. While this is an acceptable process in which to decorate the uniform it creates two extra steps–matching the ink color to the color of the die cut numeral, and then the transferring of the numeral to the uniform. If this is the process you are using now, this paper will eliminate these last two steps by demonstrating the proper techniques to direct print 100% nylon and polyester uniforms correctly and make the challenges easier to overcome so printing athletic uniforms can become a profitable part of your business instead of a burden.
Determining Fabric Content–Is it nylon or polyester?
Before beginning production on any athletic uniform check the fabric content of the uniform. Just recently we spoke to a customer who printed athletic gold ink on twelve navy uniforms for a youth basketball team. Guess what, eight of the uniforms had a beautiful gold printed logo and number while the remaining four had turned a hideous, greenish gold color a few days later. Upon further inspection, when both uniforms were placed side by side under a bright light and inspected closely, you could see a slight shade variation in the navy fabric between the good and bad prints. Upon further inspection, the customer discovered that the four uniforms with the greenish-gold prints were 100% polyester and the dye had migrated through the ink film and turned the athletic gold print a greenish color.
Uniform manufacturers have turned to polyester because it is an extremely durable fabric which costs less than nylon. This customer just happened to the unlucky guy who received a shipment when the manufacturer was changing his fabric over from nylon to polyester. Having learned a lesson the hard way, this customer will be inspecting all fabric content labels from this moment forward. Also, when you read the bottom of our Technical Data Sheet where it says in bold, black letters– “CAUTION, always test this product for curing, adhesion, crocking, opacity, dye migration and other specific requirements before using in production”, it would behoove you to heed this warning. You are not printing a $2 t-shirt, you are printing a substrate which can cost between 10-$50 or even more. Ruin just one uniform and your profit is gone!
Choosing the ink–Are these uniforms to be game worn or replica uniforms?
In order to determine what ink to use you must first determine if the uniforms are to be game worn or replica jerseys. Union manufactures two specific ink series, Athletic Gloss Series (for 100% nylon) and the Polyester Series (for 100% Polyester) that are specifically formulated for game worn athletic uniforms. These inks are made with special plasticizers, pigments, fillers, resins and dye blockers to give prints the gloss, opacity, color brightness, bleed resistance and durability characteristics needed to survive the pounding of a full season as well as surviving the numerous laundering to remove grass stains and perspiration. These inks are typically more expensive than regular plastisol inks. If you think you can get away with using general purpose inks just because they are youth uniforms for the local Pop Warner football team, please think again. Because of the budget restraints of small colleges, high schools and youth sports teams, these game worn uniforms sometimes have to survive several seasons. Inks are not the place to cut corners.
If you go anywhere in public you see fans sporting the logos of their favorite teams on what looks like the real uniform of that team. Unless it is the die-hard fan that has to have the same shirt that Greg Maddux wears when he pitches for the Braves, he or she is wearing what is called a replica jersey. Replica jerseys are exact copies of the uniforms worn by professional and college sports teams including styling, trim and logo color. However, the likeness stops at the look. Generally, these jerseys are not constructed of the same materials as game worn jerseys and do not command the same price. Many of these jerseys are constructed of 100% polyester which again, makes it important to check the fabric content prior to production. Because these jerseys are only worn to the store or ball game and do not have to survive a 162 game season, a regular high opacity or low bleed plastisol (again check fabric content) that provides good coverage and easy printability can be utilized with excellent results.
Do I need to add a catalyst to my ink?
The most misused additive in the screen printing industry is the nylon bonding agent (catalyst) printers add to help plastisol inks bond to nylon jackets. Nylon jackets are woven and have a slick finish leaving plastisol inks nowhere to bond unless catalysts are added to glue the ink to the slick surface. Even though uniforms are made of nylon, the difference is they are a knitted nylon. To illustrate this point, take a nylon uniform and hold it up to the light, what do you see? You see light coming through the different fibers that have been knitted together to form the uniform. Anytime you have a fabric where you can see the fibers the ink will surround the fibers and form a mechanical bond during the curing process without the aid of a catalyst.
Nylon uniforms normally pose no threat for dye migration. As long as your dryer is hot enough to reach the recommended cure temperature of the ink and low enough not to melt or scorch the fabric, everything will be ok..
Are there special screen making considerations?
Because of the thicker ink deposits needed to give uniforms the athletic print look and durability you will need to alter your screen making techniques. Uniform printers typically use mesh counts in the 83-110 range depending upon the color of the fabric. Dark uniforms, particularly polyester should be printed on 83 mesh count screens while white, light colored fabrics, nylon or polyester can be printed with 110 mesh count screens.
Since ink deposit is directly related to the emulsion thickness on the print side of the screen you may need to coat your screens an extra time on the print side (bottom). This extra coat will also increase your print sharpness. Use the following guidelines for this process:
High solids, one part emulsions (Photopolymers)- Put one coat on the print side, turn the screen over and put one coat on the squeegee side. If you not satisfied with ink film thickness using this technique let the emulsion dry completely and then put an additional coat of emulsion on the print side (bottom).
Dual cure emulsions–Put two coats on the print side, turn the screen over and put one coat on the squeegee side and let dry. Complete the process by coating the print side of the screen again.
Diazo emulsions–Same technique as dual cure emulsions except due to the lower viscosity of this type of emulsion a third coat may be necessary.
Remember, always dry your screens horizontally, print (bottom) side down. This allows gravity to pull the emulsion downward on the print side giving you the thicker coating you are trying to achieve.
Will I need a special press for printing uniforms?
Uniforms are generally printed on manual presses because of their relatively short runs so any manual press on the market today will suffice. However, if you are going to do this full time you may want to invest in a numbering machine. A numbering press contains a short and very wide screen (approximately 20″ tall by 6’ wide) and contains the numbers 0-9. The screen is held in a carriage that slides back and forth depending upon the number to be printed. Registration guides on the press help line up the number in the correct position on the uniform for both single and double digit numbers.
Another method used to print numbers is with paper or plastic number stencils where the numeral has been die cut from plastic, thick parchment paper or card stock.
In this process a regular screen is coated using the coating methods described earlier. For a 6″ number, the screen maker will utilize a 10″ square mask cut from rubylith or some other opaque medium and place this on the screen as the image. This leaves a blank open image area approximately 1″ square in size around the actual number. The printer then places the uniform on the platen and positions the number stencil in the correct position on top of the jersey. The screen is then brought down over the number stencil, and with the numeral acting as the image prints the numeral upon the uniform. After printing, peel the stencil from the back of the screen and repeat this process on each uniform. For larger numbers such as 8″, 10″ or 12″ a larger mask will be needed to compensate for the additional number height.
Even though paper stencils cannot be reused, there are plastic stencils available that may be cleaned and used repeatedly.
Is there a “Rule of Thumb” for the placement of logos and numerals on uniforms?
There is nothing worse than to see someone wearing a uniform where one half of the number is tucked into the uniform pants or a front logo on a lady’s jersey printed too low. Equally as bad are numbers that inconsistent in placement. The following guidelines should be used for the positioning of logos and numbers:
Front Logo for crew neck uniforms and v-neck style jerseys-Logos should be place no more than 1 _” —2″ below the neck seam properly centered. Extra caution should be taken for double digit numbers that contain the numeral one such as 21 or 12. The numeral one is considerably thinner than the second number and will throw the horizontal centering off. If a number is to be placed below the logo, place it a minimum of 1″ below the logo. For large width logos make sure there is a 1″ space between the edges of the logo and the sleeve seam especially on raglan sleeve jerseys. Drop the design down until you can achieve this 1″ side clearance. If a logo goes below 2″ down in order to achieve this side clearance consideration should be taken to reduce the size of the logo.
Back numbers– For numbers, place the number approximately 7″ below the collar of the shirt for men’s uniforms. For lady’s uniforms place the number approximately 6″ below the color trim of the shirt to compensate for the height difference between men and women. If names are to be used they are generally placed above the yokes on football jerseys, especially if the number is 10-12″ inches in height. All names and numbers again should not be closer than one inch to the side seams of the sleeve or jersey and properly centered. Remember our little warning in the front logo placement about the numeral one. For names not placed above the yoke on football jerseys and for other sport uniforms such as soccer, volleyball, basketball etc. use the number placement guidelines and place the name approximately 1 _-2″ above the number.
For placing numbers on both fronts and backs of jerseys some printers use a less than scientific approach to vertical placement. In this method they will draw an imaginary horizontal line across the jersey that connects the bottom of each armpit. Then determine the vertical center of the number and place the vertical center on this line.
Shorts- Logos should be placed 2 _” from the vertical seam and 1 _” above the bottom seam of the shorts.
Again, these are only guidelines for placement. Special consideration for the best aesthetic appeal will have to made using the printer’s and customer’s judgment for oversize numbers and logos.
Are there any special printing considerations when printing athletic uniforms?
Special consideration should be taken when printing light colors versus dark colors, mesh fabrics versus solid fabrics and nylon fabrics versus polyester fabrics.
One color numbers or logos should be double hit to ensure good coverage and accurate reproduction of the color. With a medium (70 durometer) squeegee make sure the first stroke pushes the ink down into the fabric (not through the fabric). This will give the ink a sufficient area to wrap around and adhere itself to the fibers and form a strong mechanical bond. The second stroke should be made so the ink is cleaned from the screen and lay on top of the first coat. Good athletic printers have developed a technique so the second coat lays on top of the first coat and does not push the first coat further into the fabric.
Two color numbers and logos should not only be double stroked but also flash cured between colors particularly on dark garments. Flash curing between colors will ensure that each color has the same finished look and also help increase opacity. The artwork for uniforms is generally “trapped” which means part of the second color overlaps or touches the first color to ensure proper registration. Follow the same guidelines as printing one color numbers or logos except flash cure between the first and second colors. If a white or other light colored ink is to be printed as the outline or on top of the darker color ink, an athletic ink with a non-migrating pigment must be utilized for the first color. Non-migrating pigments will not migrate up though the light color causing a shift in color of the top print.
For polyester uniforms a low bleed ink must be used on all colors except white or light colors and a print/flash/print technique should be used to form a good ink film thickness that will reproduce the color, resist bleeding and give the number or logo good durability.
An extra, extra special consideration has to be taken when printing micro-mesh (small holes), mesh jerseys (regular size holes) or “porthole mesh” (large holes) uniforms. Because of these holes, the ink will go onto the printing platen and will transfer onto the next uniform. If you do not want to clean the platens after every print, simply spray the platen lightly with a repositionable adhesive, place a sheet of card stock or newsprint large enough to cover the image area of the number or logo, spray the card stock or newsprint with adhesive, and then place the mesh jersey on the platen and print. Some printers will even flash the image before removing the garment to ensure it does not accidentally drag through any of the wet ink that has been left on the platen. Discard the card stock or newsprint after each print and replace. Even though this may sound like a major pain it is much more productive than cleaning your platen after each print.
Good athletic uniform printers have taken many years to perfect their printing techniques. Upon asking most uniform manufacturers will provide at a minimal cost sample pieces of material in order for your printers to practice and perfect their printing techniques prior to producing a job. Maybe Curt Warner can handle the pressure of throwing the winning touchdown pass at the end of a game but don’t put the same pressure on an inexperienced printer by having him print an eighty dollar jersey without some training.
Are there special curing considerations for athletic uniform prints?
Most manufacturers recommend athletic inks be cured at a temperature range of 300° -320° F throughout the entire ink film. Even though these temperatures are the same as recommended for inks printed on tee shirts, extra caution must be taken. Because of the thicker ink deposits required and the different thickness of the uniform material you may need to increase the heat, slow the belt speed of your conveyor dryer or do a combination of both in order for the entire ink film to reach the recommended curing temperature.
If you have six feet or less of heating panels in your dryer, you may also need to run the uniforms through the dryer a second time. This will depend upon the thickness of the material. We have worked with customers who were left scratching their heads as to why white ink was washing off a four ply reversible practice jersey but was adhering to a single ply mesh jersey. It was simply because it was taking longer for the garment to reach the proper temperature before the ink could cure. A non-contact pyrometer was directed at the one ply mesh jersey and the temperature was easily reaching the proper cure temperature. However, when placed upon the four-ply jersey as it exited the dryer the print measured approximately 250° F. When the jersey was immediately put through again while it still retained much of the heat from the first time through the oven, the ink film easily measured the required cure temperature when measured.
Why is this? After all, isn’t heat, heat? Even though this might seem to make common sense, the answer is a resounding no and other considerations such as fabric weight, construction, moisture content and color of both fabric and ink must be considered. A plastisol screen printing ink cannot reach its proper cure temperature until the fabric does so it takes longer for four layers of fabric to reach temperature than one layer of fabric. Also, dark fabrics and ink color will absorb heat and reach temperature faster than light colors.
A good analogy is heating two different sized houses during winter. If one house is 1500 square feet (regular tee shirt material and print) and the second house is 3000 square feet (athletic uniform material and print), and your goal is to bring each house to a comfortable living climate from 0 degrees, it will take a longer time to bring the 3000 square foot house to a comfortable temperature. The same holds true for athletic prints–thicker fabric and ink film thickness, more; thinner fabric and thinner ink film thickness–less.
Undercuring results in poor wash fastness on both polyester and nylon uniforms and causes dye migration on polyester uniforms. We recommend that printers monitor their dryer temperatures several times daily. This is important when printing uniforms, especially polyester as over heating the fabric can cause just as large a problem as undercuring the ink. Polyester dyes are very unstable and start moving and looking for a place to go somewhere over 270° F. Even though the dye blockers put in inks do a good job of keeping the dyes from penetrating through the ink film at 300° -320° , you substantially limit this ability at temperatures above 330° F. One major uniform manufacturer recommends checking the fabric temperature to ensure it does not go above 330° F. Because polyester dyes are unstable and overheating is such a problem, printers should test their curing temperatures so any 100% polyester garment cures the first time through the dryer.
A relatively easy to use and inexpensive measuring device is a small non-contact pyrometer that looks like a weapon from an early science fiction movie. It has a laser pointer to indicate the exact spot where the temperature sensor reads and when the laser is positioned on the ink film or fabric gives a very accurate reading of the temperature at that particular spot and time of the curing process.. These pyrometers started out in the $900 range but lately smaller versions have been selling in the $89-$159 range. Save just one job and the unit has more than paid for itself!
Athletic uniforms may not be the easiest substrates to print but they do not have to be a major difficulty either. By following a few, simple guidelines in order to develop the proper printing techniques, understanding fabric content, ink film thickness and curing parameters you can easily make the team that plays like a winner look like a winner while also developing a profitable niche in your marketplace at the same time.
Customer testing is required and should be mandatory with this product or any new product or process before running production. Union Ink Company’s technical advice and recommendations given verbally, in writing, or by trials are believed to be correct. They are not binding also with regard to the possible rights of third parties and do not exempt you from your task of examining the suitability of our products for the intended use. We cannot accept any responsibility for application and processing methods beyond our control, nor can we accept responsibility for misuse by you of the products or use by you of the products outside the specified written instructions given with the products
Plastisol Ink Opacity and Viscosity
Reducing the ink lowers the opacity and bleed resistance, which can cause smearing. Instead of trying to achieve a soft hand by printing through a finer screen, upgrade the set-up conditions by using high-tension frames, capillary film, slightly off contact, and by printing on the surface of the fabric, being careful not to penetrate the fibers. Less ink is required for maximum coverage if you print on the surface of the fabric, and remember that maximum coverage gives maximum bleed resistance. Maximum coverage does not mean maximum ink deposit. As a matter of fact, it means less ink deposit, thus softer hand.
All-purpose plastisols (MA Series) are designed for printing through finer mesh screens resulting in less ink deposit and a softer hand. The viscosity is lower to allow better penetration into the fibers of the garment.
High opacity (MH) or high opacity low bleed (ML) products contain a high level of pigment for more complete coverage of dark colored garments. High opaque plastisols will give better opacity when printed through a coarse mesh (86 – 110 mc./in 34 – 43 mc./cm.) though they can be printed through much higher mesh counts. The viscosity is high for maximum coverage. The mesh should be chosen to print the least amount of ink that gives the desired coverage.
If you should choose finer mesh ranges for printing on dark garments, the high opaque inks will not cover as well. The result will be “grin through”. The viscosity is too high to process through extremely fine mesh counts.
Low bleed plastisols designed for printing onto polyester and polyester blend fabrics in conjunction with some reactive cotton dyes can lead to the ghosting problem. Since the ghosting phenomena is well defined, warnings regarding the use of low bleed plastisols are given in this technical data literature.
What is Ghosting?
1. Certain cotton dyes are more sensitive to oxidation/reduction reactions than other dyes, and will more easily lose color value. The degree of “fixing” of dyes on the fabrics is part of the equation. For instance, dyed fabrics that are to be printed later using discharge must have the dyes not “fixed” so the color can be removed after the discharge printing. They dyers typically do not totally react/fix the dyestuff to leave it vulnerable to further reaction. Also, they select dyes so they have the discharge potential. In the case of reactions with low bleed plastisols, dyes in the yellow, blue/violet families are more sensitive, and fabric colors using these groups of colors need pre-testing. Dyers can select more colorfast dyes, but these typically have a higher cost. Also if a dyer does not know the end use of a given fabric, then they typically use the most economical dye package, and generally, the less costly dyes will be subject to easier color removal.
2. Low bleed plastisol contains chemistries that are activated with temperature to offer some oxidation/reduction characteristics, and this is why they work on polyester fabrics dyed with disperse dyes. The recommendation is not to use the low bleed plastisols on 100% cotton fabrics. If one chooses to use a low bleed ink on 100% cotton, the combination of low bleed ink/fabric should be pre-tested to assure there is no adverse effect. There is a test procedure defined in this literature. In fact, with the influx of more imported fabrics, it is advised that all fabrics be pre-tested to assure that the quality is suitable for printing.
3. Process conditions – experience shows that the following must occur for ghosting to occur on 100% cotton:
· Certain dyes must be present on the 100% cotton.
· Low bleed ink is being used.
· Humidity be present in the garment after printing.
· Lack of full fusion of the plastisol (make the ghosting more severe)
· Heat present after the fusion step (stacked hot without proper cooling before boxing)
100% cotton has a high moisture content – the commercial moisture content of cotton is 8.5%. Some of the softeners/finishes on the fabrics can act as humectants and increase the moisture content of the fabrics, especially in areas with high humidity. Many fusion operations do not fully fuse the plastisol, nor remove all of the moisture from the fabric during fusion, and this results in two problems:
1. Because there is moisture in the fabric, the heat of evaporation cools the fabric thus reducing the degree of fusion of the print. Until all the water in the fabric is evaporated, the fabric and the print will not go above 212°F (100°C).
Because the plastisol has not been fully fused, the chemistry used for low bleed purposes has not been completely reacted, thus residual reactive chemistry that can interact with dyestuff is available.
2. Residual moisture left in the fabric contributes to the reaction between the low bleed chemistry and the dyestuff, especially in the presence of elevated temperature. When garments are removed from the oven belt and they are still hot, they should not be stacked until they have been cooled. The stacking acts as insulation to hold the heat and if moisture is present and the plastisol is not fully fused, then conditions are prime for a problem if the poor resist, reactive dyes are present on the garment.
· Print on suspect fabric with selected plastisol ink and cure normally.
· Lay test fabric on transfer machine & moisten (spray with water) the print area.
· Fold part of the unprinted fabric over the moistened print area.
· Heat press at 250 °F (130 °C) for 30 minutes.
· Remove from press, unfold and check the unprinted portion of the garment for ghost effect.
Squeegee Selection and Management
Of all the components involved in the screen printing process, the Squeegee is one of the most important. A simple piece of rubber can affect the overall quality of the end product. A dull or nicked Squeegee will not allow the ink to transfer evenly through the screen. If the inside of the Screen is wet with ink residue, the Squeegee is not performing as well as it should or could.
A number of factors affect the Squeegee performance. Abrasion with the screen slowly dulls the squeegee, reducing its ability to shear the ink from the screen. Harsh solvents will also degrade the Squeegee. Solvent based inks and UV inks can drastically limit the life expectancy of a squeegee, often causing the Squeegee blade to swell or soften on the press. In fact, manufacturers to dissolve excess polyurethane in their storage tanks use some ink ingredients, such as NMP. All of these factors can ultimately affect print quality.
Selecting a Proper Squeegee:
Squeegees are made from 3 basic types of materials:Rubber, Neoprene, and Polyurethane. The least expensive Squeegees available are those constructed of natural rubber. While commonly used in the education part of the screen printing industry, rubber tends to suffer from poor abrasion resistance and poor resistance to strong solvents. Neoprene, a synthetic rubber compound made from a chroline derivative of acetylene, is also a popular Squeegee material. Neoprene is slightly more expensive than natural rubber, and it offers better chemical and abrasion resistance.
Polyurethane, a syntethic plastic material, is often used to make Squeegee designed for extended use, and for automatic and semi-automatic equipment. While urethane is more expensive than rubber or neoprene, it offers a much better resistance to both physical and chemical abrasion. Most urethanes used in the screen printing industry are MDI based Polyester. The reason being the MDI urethanes offers the best abrasion resistance of any urethane on the market. Polyurethane Squeegees are the most popular of all Squeegees. They are cast in liquid form in open molds, close molds or centrifuges. The material is a thermoset plastic, and cures when exposed to heat for a period of time. The material is made in sheets or individual sections, and then cut to size for shipping. The most common sizes are the following: 3/8 x 2 for general Screen printing(graphics, textile, glass, electronics), 3/16 x 1 for bottle, cd, and high speed automatic presses.
When selecting a Squeegee, the first task is to determine your desired durometer, or hardness. The durometer is the value that reflects the physical hardness of the Squeegee material. The Squeegee durometer values from 50A to 95A. This is measured by a durometer gauge, and measured based on standards established by ASTM procedures. (American Standard Testing materials) . For the sake of simplicity, we will call soft – 60A, medium – 70A, and 80A – a hard Squeegee, and 90A -extra hard. Plastics/Squeegees are measured in various scales of hardness. Shore A scale is the most widely used for measuring Squeegee material. The values are based on readings There are many different styles of durometer gauges available on the market. All of the durometer gauges on the market have a dial indicator with a small needle head that measures the hardness of the Squeegee. A durometer gauge is identical to a tension meter. Like a tension meter, a durometer gauge should be calibrated on a regular basis. (1 time per year). The small needle head penetrates into the material, and indicates the hardness of the rubber.
Typically the Substrate and the screen mesh will directly determine the durometer selected. For example, if the substrate has an irregular or rough surface and requires a coarse mesh, then a squeegee with a durometer between 60 and 70A is recommended. If the substrate is smooth, however, and a high Mesh count is being used, a harder durometer squeegee between 80 and 90, should be used. The most popular durometer regardless of industry specific, is the 70 durometer blade. Why? The Squeegees job is to shear the ink, and transfer the ink through the screen. So, the blade needs to be rigid enough for this, yet needs to be soft enough to adapt to the contour of the Screen. A 70 durometer blades gives the printer the best of both worlds. A softer blade, but not soft enough to the point where it will roll over and loose ink shear. See diagram below: Middle of the road makes the most sense when it comes to Squeegee selection. However, ink is also a determining factor when selecting the durometer of the Squeegee. The more aggressive inks such as UV inks cause more harm to the blade than a standard Plastisol or water based ink. The harder the material, the more solvent resistant the blade. Therefore, to eliminate swelling and chemical breakdown, use a harder durometer Squeegee.
The printing equipment itself can also affect squeegee choice. Hard durometer Squeegees are normally recommended for use on high speed automatic presses due to the high degree of abrasion that occurs during a production run. Softer durometers Squeegees are typically used for low-pressure low speed manual and semi-automatic presses. The harder the material, the lower the coefficient of friction, and the less abrasion on the screen. The Squeegee durometer directly affects the way the ink is deposited. A soft Squeegee will deposit a thicker layer of ink than a harder Squeegee. Thus, a soft Squeegee would be used for putting a full coverage image onto the substrate.
Most manufacturers of Polyurethane Squeegees color-code their Squeegees based on the hardness of the material. By color-coding, it makes the Squeegee easier to define for a particular job. For Example, one manufacturer has a color scheme of.
- 60-A red,
- 70-A green
- 80-A blue.
Others use an orange, blue, and red color-code system. Unfortunately, there aren’t any standards for colors. The printer knows if they want a heavy ink deposit, they should use a 60 durometer, but it could be red or orange, or even another color. For best results, the printer should invest in a durometer gauge.
A screen printer can purchase a squeegee with many different profiles. The profile of the Squeegee determines the thickness of the ink deposit laid down, and the effectiveness of the Squeegee on different substrates. Available edge profiles include a square edge, a square edge with rounded corners, a round edge, a double-sided beveled edge, and a single beveled edge. Squeegees with a square edge are the most common, and mainly used on cylinder, textile, and manual presses. Rounded Squeegees are generally limited to the textile industry, and are used when a very heavy deposit is required. Beveled Blades are typically used for printing rounded surfaces where fine definition is required. While double sided beveled blades are more efficient on high-speed automatic machines. Single Beveled blades produce excellent results when printing heavy Solids.
Some printers will round the Squeeegee with a small radius to get more ink deposit.There are tools available or grinding wheels for putting different radiuses/profiles on Squeegees. However, the most effective, and the best shearing edge is still a 90 degree or a straight edge profile. The reason being is the following: Anytime you round a squeegee or put a tapered edge on it, the the blade looses it sharpeness or cutting edge. A rounded Squeegee isn’t really shearing or transferring the ink, but rather the blade is now spearing the ink across the screen. A good test of the principle is to look at the screen when the blade is done printing, Is there any ink left in the screen? There are many different parameters that can changed in the printing process to achieve the same results: ink Viscosity, mesh count, mesh tension, & Off Contact. I am firm believer that a Squeegee job is to transfer the ink, and the best angle of attack is a 90 degree edge. If you want to lay an Adhesive down, then I will agree a rounded edge may be the right choice.
Maintenance & Storage:
Proper Squeegee maintenance is vital to producing quality printed images. For example, when printing with aggressive inks, each side of the blade shouldn’t be used for more than 4 hours. Implementing a rotation schedule with the blades will dramatically increase the overall life of a Squeegee. By using the Squeegee for 4 hours at a time, and then replacing with a new one, the blade will last much longer. Squeegees are like car tires. If you rotate them every 5000 miles or 4 hours, they will last longer, and not develop a curl or swell to them. Do not use the Squeegee till Failure. This will cause problems with the blade when re-sharpening. Excessive swelling and softening can result from printing with the same Squeegee edge for an excessive period of time. If ink residue begins to build up on the inside of the screen, the Squeegee should be replaced with a new one. A used Squeegee will recover after 24 to 48 hrs, and can be resharpened and returned to the printing press. The Squeegees should be laid out flat when not in use. Polyurethane Squeegees should always be stored in a dry and relatively cool area. (60 to 70 degrees F). The material should be laid out flat to eliminate any curl to the Squeegee rubber. Manufacturers and distributors ship the material in coil form for shipping purposes only.
You should always lie out flat as soon as the material is received into your facility. Occasionally, Squeegees stored below 60 F will increase in hardness. This will not affect the performance of the rubber, but it will affect the ink deposit performance of the blade. It is a good idea to test Squeegees with a durometer gauge during a long production run. Some materials will soften when exposed to solvents for a long period of time. If the rubber softens to more than 5 to 7 points, it is recommended that you replace the material.
Resharpening can be performed with either a belt sander, grinding wheel, diamond wheel, Hot knife, cold cutting blade, or rotating blade. All methods have pros and cons. Some Squeegees sharpen better than others on different sharpeners. For example, some Polyurethane materials have more elastic properties than others. Some have better abrasion properties, and some cut easier than others. Some melt when put under pressure on various grinding wheels or sanding belts. Every Squeegee should be tested on a sharpener prior to
There are many different ways to sharpen a squeegee, and each blade should be tested with the sharpener of choice. The best way to evaluate a sharpener is to have an equipment company sharpen a blade for you, and test the sharpened blade on your most critical job. See the enclosed diagram for various types of sharpeners on the market today. Other items to look for in a sharpener are the following: Repeatability? Cost? Consistency in height (is the sharpener true to the Squeegee holder)? However, the most important thing in evaluating a sharpener is print results.
Most companies will set some guidelines on how low or how much material they will sharpen off a squeegee before it starts affecting print quality. A normal press will accommodate as much as a ½” of variance from one blade. The industry norm is a 3/8 x 2″ blade depending the equipment being used, and most companies will sharpen a squeegee until it goes down to 1.6 to 1.75″ in height. However, this is a case by case basis. Most companies printing t-shirts will allow more of a variance in the height of the rubber. Electronics, & CD printers can’t allow much height variation. They choose to throw the rubber out after a production run. Remember, the durometer of the rubber is important, but the unsupported height of the squeegee rubber ultimately determines how much flex a Squeegee will have on the press, and how much ink will be deposited. It all depends on the application, and how critical is the level of ink deposit. One must look at the parameters involved, and set height standards for the Squeegee.
One of the biggest innovations in the past 15 years is the increase in composite Squeegees, or multi durometer blades. There are many products on the market that incorporate fiberglass inserts, and multi layered blades. The reason stems from the increase in the need for better print quality. More and more printers are being pushed to the upper limits of Screen printing, and thus the increase in the number of Squeegee innovations to the market place. Referencing back to the durometer section of this article, the most popular blade regardless of industry is the 70 durometer, or medium hardness blade. The reason is that a 70 durometer is in the middle of the road: (not soft, not hard). However, when problems arise on a press, most printers will increase the Squeegee pressure to get more ink lay down. The increased pressure on the blade will cause the blade to bend or roll over. Therefore, by using a dual durometer stacked, dual durometer vertical, triple durometer, or a fiberglass composite Squeegee, the printer can get better print quality by using a blade that is supported right down to the edge of the Squeegee. Multi-durometer Squeegees & composite Squeegees use a softer material on the printing edge, and then use a harder material or fiberglass product to give the blade some rigidity.
Dual durometer blades were the first real innovation in Squeegees. By casting a hard durometer on to a soft material, the printer ultimately benefited by having a Squeegee that had a soft print edge, and a rigid backing material supporting it. This had been done for years with stainless steel backing plates on many presses. There is a big disadvantage of a dual durometer blade. The blade can only be used in one direction, and after long periods of time, the blade will eventually develop a curl or set in one direction. Triple durometer Squeegees have taken the place of dual durometer Squeegees. The triple blade ( sandwich style) has the harder durometer in the middle of the Squeegee rather than one side, and a soft or medium hardness on the outside. This blade can be used in both directions.
Durometer isn’t as important at the unsupported height of the blade. Unsupported height is defined by the distance from the edge of the Squeegee to the point where the Squeegee goes into the holder. See drawing below. Understanding this parameter, will answer why there has been an increase in Squeeegee innovations. One manufacturer, Printer’s Edge has developed Squeegee holders that will maintain the same unsupported height of the Squeegee even after the blade has been sharpened. This is called an indexable Squeegee holder. Why is this important?
If your customer is requesting a color tolerance on a particular graphic, it is very important to control the height of the blade. This will ultimately give you more ink deposit control In addition, flex control Squeegee holders have been introduced over the years to help with blade buckling. The advantage of a flex control holder is single durometer blades can be used, and you don’t have to spend the extra money on a triple or multi-durometer Squeegee.
All of the innovations come with a price so one must weigh the advantages over the costs. The fiberglass blades are very expensive, and sometimes difficult to sharpen. Being a multi layered blade with 2 different materials creates problems for both grinding wheels, and sanding belts. In fact, you can’t cut the fiberglass blades with any of the cutter style sharpeners on the market. In addition, they have limited life span because the urethane is only 3/8 to ½” on the blade. Triple durometer blades work well for printing fine half tones, or four color process work. The blade is soft enough to conform to the screen, and the substate yet rigid enough to transfer the ink thru the screen onto the substrate. Stacked dual durometer blades give the printer 2 edges to use, and more support in terms of unsupported height. Triple, and dual durometer blades are approximately double in price to single durometer blades. The fiberglass blades are approximately 4 to 5 times the cost of a single durometer blade. Single durometer blades are still the most cost effective. In conjunction with special Squeegee holders, the printer can achieve the same results as a multi-durometer blades or fiberglass blades. However, this also comes with a price. The indexable, and flex control holders that are available are approximately 30 to 40% more expensive than conventional Squeegee holders, but the big advantage is you can use a less expensive single durometer Squeegee.
Selecting a Squeegee is not the easiest job. As a printer, you must consider all the parameters involved when selecting the right Squeegee. The squeegee blade brings the total printing system together: Pre-press, image, ink, substrate, and press: All of these variables can be controlled, and should be looked at individually, and together. The Squeegee is only one of the variables, but is one of the most critical. Don’t let the Squeegee be the difference between scrap, and sellable product.