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Davis International
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Frequently Asked Questions About Textile Screen Printing

What do I use to clean ink from screens?

When changing colors, cleaning a screen on press, or to save the screen for future use... you should use a press wash. They usually evaporate quickly and don't leave any residue. When cleaning ink from a screen to be reclaimed... you should use an ink wash (aka screen wash). There are several to choose, but most are biodegradable and will emulsify (break down) the ink. It's recommended to use a filtration system to filter out the solids (often the cleaning solution can be reused) before going down the drain (plastisol inks are deemed legal landfill once they are set into a solid form through curing). The filters containing the ink solids can be cured or sent to a waste treatment facility to ensure they are disposed of properly. Consult your local city and state regulations for the proper disposal of any screen printing products.

What is the "shelf life" of your products?

By maintaining proper storage conditions, plastisol inks can have a shelf life of several years. Two-part inks, such as nylon inks, once mixed (with catalyst) usually have a limited shelf-life of 8-12 hours. Refer to your inks' technical data sheet for more info. Plastisol  inks should always be stirred before use. Ink separation can occur, but it can usually be blended back together with a good stirring. Plastisol inks are thixotropic meaning that the more they move, the better they will flow... so stirring all inks before use will usually make them print better.

What does "flash" mean?

"Flash" refers to a heater used to "gel" the surface of a printed ink on press (so it is dry to the touch, but not cured). This allows overprinting or printing of other inks without the wet ink lifting off the garment. Often light inks printed on dark garments are print-flash-print for maximum opacity. Flash can also refer to the actual "flash cure unit".

What does "cure" mean?

A complete cure of plastisol ink occurs when the entire ink film fuses and becomes a single solid entity. For an ink to fuse fully, the entire film thickness must reach its correct cure temperature. Different plastisol inks will have different cure temperatures (usually ranging from 270-325°F).

Why is "off-contact" printing important?

Screen-printing was designed as "off-contact" so that the ink will release from the screen once the squeegee has passed the desired image area. Without off-contact, the screen will not lift up out of the ink creating an undesirable print effect.

Are plastisol inks considered hazardous and are they safe to use on children's garments?

Plastisol inks when properly handled and used are considered "non-hazardous". Lead-free plastisol inks properly applied are considered safe for children's garments. Most plastisol inks are now phthalate compliant or phthalate free.

The majority of garment printers in the United States currently use PVC-based, phthalate-free plastisol ink. Most ink manufacturers offer this ink system because it conforms with CPSIA guidelines and meets the 100 parts-per-million lead levels as outlined above. Unless we see a major industry shift away from PVC-based ink, these current phthalate-free plastisols will remain the most popular type of textile ink for garment decorators for many years to come. - See more at: http://impressions.issshows.com/screen-printing-process/Todays-Textile-Ink--6995.shtml#sthash.6VH1Zbax.dpuf
The majority of garment printers in the US currently use (PVC-based) phthalate-free plastisol ink that conforms with CPSIA guidelines. Some companies may demand a PVC-free printed product, which has lead to the development of PVC Free inks, and increased use of high-opacity water-based and discharge inks. 
The majority of garment printers in the United States currently use PVC-based, phthalate-free plastisol ink. Most ink manufacturers offer this ink system because it conforms with CPSIA guidelines and meets the 100 parts-per-million lead levels as outlined above. Unless we see a major industry shift away from PVC-based ink, these current phthalate-free plastisols will remain the most popular type of textile ink for garment decorators for many years to come. - See more at: http://impressions.issshows.com/screen-printing-process/Todays-Textile-Ink--6995.shtml#sthash.6VH1Zbax.dpuf
Some children's sleepwear may also be required to be "flame-retardant".

Are your inks safe to use?

Yes, used properly according to our recommendations, our inks are considered safe. Always check the MSDS (Material Safety Data Sheet) for any product you are going to use.

How or why should I modify an ink and when?

Knowing how, why, and when to modify an ink comes with experience. Most commonly, printers modify inks with reducers to bring down viscosity when inks are too thick, or with soft hand extenders to soften the hand or feel on white or light colored garments. Be sure to follow the manufacturers' guidelines and USE a scale. Be careful! Over modifying an ink or using incompatible products may create problems.

Why are there so many different "whites"?

Because it is such a critical color, ink manufacturers formulate specific white inks to accommodate the wide range of garments and applications printers are likely to run into. Printers can select white inks based on such factors as bleed, opacity, flash and cure characteristics, or printability.

What is the best "white" to use?

Unfortunately, there is no simple answer to this question. Ask yourself what you want from your white ink. Your answer should depend on the garment, art, desired effect, press, dryer, etc. Give us a call to see which white we recommend for your printing needs.

Why is my ink so thick and what can I do or use to thin it?

Plastisol inks can thicken over time, just sitting on the shelf. We always recommend that you try stirring or mixing the ink before each use. This will help break down the "false body" that inks can get after long periods of storage. If stirring or mixing is not sufficient, use a "Curable Reducer" at the recommended percentages.

At what temperature do your inks cure?

The short answer is when the entire ink film thickness reaches its specified cure/fusion temperature. That temperature is provided on your specific ink's product bulletin. Keep in mind that thicker ink deposits (e.g., High Density) take more time to reach their specified cure/fusion temperatures. Faster fusing or low cure inks will reach their fusion or cure temperatures more quickly than conventional inks.

How long does it take for your inks to cure?

There is not a single easy answer. Many factors play into how long it takes to completely cure an ink. Are you using an electric dryer or a gas dryer? Does the print have a thick ink deposit? Are you printing on T-shirts or fleece? Measuring the ink temperature on the garment, as it passes through the dryer, is the best way to determine the time it takes for your inks to cure properly. Remember that it is important that the entire ink film thickness reach the specified cure/fusion temperature.

How do I test to make sure my inks are cured?

A "Wash Test" is the best method. Take a sample print, cut it in half, and wash it 3 to 5 times in a conventional washing machine with 3 pairs of jeans or towels. Set the washer for 'Hot Wash/Cold Rinse'. Set the Dryer for 'Cotton/High' and dry for 30 minutes. Complete 3 to 5 wash cycles and compare the "washed" sample to the "unwashed" sample. If you see cracking of the ink film or ink loss, your inks are likely under-cured.

What temperature and what length of time are needed for your inks to "flash" cure?

Most inks will "gel" (flash) when the ink film reaches 220°F to 230°F (104°C to 110°C). There are 3 factors that affect the "gel" or "flash" of the ink: the temperature of the flash, the distance of the flash from the printed image, and the time the printed image is exposed to the heat. As a rule, you want to flash the ink film until it is just "dry to the touch". Over-flashing inks can cause inter-coat adhesion problems and make the inks very "tacky". Check your flash cure unit to see if it has temperature and airflow controls. These can help you better control your flash cure process.

What happens if I don't cure the ink properly?

Many things, none of them good! Typical problems that arise from improperly cured inks include: ink washing off the garments, cracking of the ink film, loss of color, and bleeding of the garment color(s) into the ink film.

Why do I need to "flash"?

There are several reasons. Flashing enables you to print one coat of ink on top of another - e.g., a color on a white base. You also might flash an ink to keep wet ink off the back of your screens. Some inks, such as glitters, metallics and high densities, are not designed to be printed "wet-on wet". They should be "flashed" when printing in sequence.

Can I cure my inks with a flash cure unit?

We do not recommend it! Although it is true you might be able to get the ink hot enough, a flash cure unit is not a good substitute for a properly operating dryer. Using just a flash cure, you could easily overheat the film surface yet under-cure the rest of your ink film, at the same time! Not a good idea - don't do it!

How do I know if my inks are cured properly?

Your printed garments pass the wash test! (See above - "How do I test to make sure my inks are cured")

How do I measure ink temperature?

There are 3 basic and easy-to-use temperature measurement devices you can use. First, a "heat tape" can be applied to the garment before it passes through the dryer. The tape will indicate the peak temperature of the garment within the dryer. Second, an infrared "Ray-Gun" can be used to measure the surface temperature of a printed garment as it exits the dryer. All you have to do is point the gun at the garment as it comes out of the dryer. And third, a "Thermo-Probe" can be placed in the "wet" ink film or on the garment to measure real-time temperatures as it passes through the dryer. Recording those temperatures at say, five second intervals, will give you a good profile on how well your dryer is working. You may be surprised with the results.

Nylon Printing

Can I use 'regular' plastisol to print nylon jackets or do I need special nylon inks?

Our nylon series inks are specifically formulated for nylon jacket and woven nylon materials. They have been formulated for superior adhesion and abrasion resistance. Adhesion to nylon is difficult to achieve with regular plastisol inks, but many people have had success using regular plastisols on nylon by adding an adhesion catalyst to the ink.

Why is the ink coming off the jackets even though I used "nylon ink"?

Did you use catalyst? Did you mix it correctly? Was the ink properly cured? These are the first things you should determine. It's possible that the jackets or nylon materials you have contain a water-repellant coating on them. This coating often prevents inks from properly adhering to the material. Try cleaning an area of the nylon with Rubbing Alcohol. Then place water droplets on the area you cleaned and the area you didn't touch. If the water is absorbed more quickly into the area that you cleaned with alcohol, the jacket likely has a coating. Clean the areas of your jackets that you will be printing before you print. Change your cloth or rag frequently while cleaning; you don't want to re-deposit the coating back onto the jacket.

Can nylon inks be printed without catalyst?

Yes they can, but not on most Nylon materials. Nylon inks can be printed on cotton or cotton/poly blends without having to use a catalyst; but nylon inks tend to have a stiffer hand feel than other regular plastisol inks.

Tips for Printing Nylon Jackets

Other FAQ:

We tried to get a good exposure yesterday, but screens just took forever to wash off. What gives?
 
Let’s first talk about the purpose of exposure. At minimum, exposure is a combination of the positive, the stencil and the UV exposure energy to cause a reaction with the sensitizer that cross-links the stencil in the mesh.
 
When an image area is hard to wash out, consider that the purpose of UV exposure is to change the stencil from something that will dissolve with water into something that won’t dissolve or breakdown with water. If the stencil “crusts” in the mesh, no matter how long you expose, it is doing exactly what it is designed to do when exposed to invisible UV energy—cure, harden and resist dissolving with water. It’s the job of the positive to protect the image area from changing (and resisting dissolving). The positive stops UV energy so the image area dissolves easily with water and rinses down the drain. An important question: is the image area dissolving as it should?
 
If the image area is ‘crusty’ or doesn’t dissolve with water and rinse down the drain, your positive failed you like a raincoat made of cheese cloth. Or, there’s been a storage failure and your storage area is not safe.
 
Many people incorrectly compensate by under exposing but they haven’t thought the problem all the way through. Exposure is easy—if it doesn’t dissolve out of the mesh, it was cross-linked somehow with heat or invisible UV energy. If the stencil dissolves, it wasn’t exposed with enough UV-A energy to cross-link.
 
To establish a base time for washout, make a very small (3" X 6") coating on a screen and let it dry to the touch. Next, take it to the washout area and time how long it takes to dissolve. Don’t expose it, just wash it out. That time is your standard for washout (for that particular mesh and coating). Now, discover where/how the stencil is getting exposed.
 
All quality control and measurement is based on comparison. Next time you expose any screen, test if the positive completely stops UV energy. Tape a dime (or any thin coin), or a piece of aluminum foil in an out-of-the-way area of the coating. Since you covered a patch of stencil with a guaranteed UV stopper, it should wash out like a dream, even if you exposed it for an hour. If the dime area doesn’t wash out, your stencil was already exposed in the storage area.

Is it necessary to coat both sides of the screen? If so, why?
 
It is very important to follow the correct procedure when coating a screen. First, coat the print side of the screen with firm, even pressure. Next, turn the screen 180 degrees and coat the ink side. You want a shiny coat of emulsion on the print side to provide a nice stencil for maximum ink deposit, but want the emulsion to have a good grip on both sides of the mesh- for maximum durability once exposed.

Why does my under base print have a rough texture?
 
The ink film has a rough surface because it hasn’t been properly sheared to flow, which allows it to remain opaque and keeps it from penetrating through the shirt to the platen.
 
Classic screen printing ink is a high-low-high, multi-viscosity product. Under the high shearing force of the squeegee or stirring knife, the ink viscosity should drop and the ink will flow into the open area of the stencil, level, then quickly recover its resistance to flow since there’s no longer a shearing force. If the ink is hanging in the mesh, it wasn’t flowing. (This is why ink manufacturers advise stirring the ink when it won’t pour in the screen. It usually takes a few practice strokes with the squeegee to “warm” up the ink so it flows.)

Slow squeegee speed (low shear force), doesn’t change the resistance to flow (viscosity) of the ink enough for it to flow smoothly through the mesh. More blade angle will push more ink through a mesh opening like toothpaste from a tube. For higher shear and better ink flow, increase squeegee speed. Higher durometer and hinged blades that don’t bend under high mesh resistance print best, whereas using more blade angle will just drive into the porous shirt like roots, but that doesn’t mean the ink was flowing.
 
When the mesh pulls itself out of the ink film, the ink naturally sticks to the mesh or shirt; it doesn’t flow out of the screen to leave a smooth image on the shirt surface. The ink that was intended for the shirt surface gets split like an Oreo cookie. Since the ink didn’t flow, the mesh intersections form raised areas that have a rough texture (usually called ‘mesh marks’ or ‘orange peel’ texture).
 
Printers' often reach for reducers to help the ink to flow, but they should first stir the ink thoroughly first. Adding too much reducer may reduce the opacity of an otherwise high opaque ink.

If you don't have enough "off contact"... when you lift the screen, you are probably also splitting the ink leaving an orange peel effect to the ink surface. Use the off contact adjustment on your press, or use some spacers to create off contact: cut a piece of cardboard from a carton that is about 2" X 3" and tape the cardboard to the neck of the platen. When you bring the screen down, the mesh should not be touching the shirt. You can test by pushing a squeegee down in the image area. While holding the squeegee down, push on the mesh on either side of the squeegee. The mesh should give, i.e., be off-contact, while the mesh under the edge of the squeegee blade is touching the shirt. If the mesh is not off-contact, then the tension in the mesh is inadequate for quality printing. The cardboard keeps the mesh off the shirt and allows the mesh to peel off the shirt as you print. This is a simple, but effective solution.


What type of platen adhesive should I use for screen printing garments?
 
Most printers have several different types of platen adhesive in stock for various needs. To determine which to use, consider the following: A spray or mist adhesive is the most popular and is great for printing several quick samples or a short production run. There are also heat-resistant formulas available for use with a flash cure. However, there is a lot of overspray which releases chemicals into the air, contributes to waste, and may get into other parts of your print setup.

When printing heavier garments, use the web-type spray adhesive. This type is thicker and may puff up to create more surface for fleece or other fabrics with more loft to adhere to.

Another great adhesive is the economical water-base adhesive that can be applied with a brush, squeegee, or spatula. Simply use a damp sponge to reactivate the adhesive and clean up can be done with water or alcohol.

For larger-volume print jobs, liquid bulk adhesive is great. These can be rolled on, brushed on, or sprayed on using a compressed air sprayer.  Several manufacturers sell corresponding sprayers for their bulk adhesive products.

There is also roll or sheet adhesive. These products are similar to double-sided tape and cover the platen evenly if applied correctly.  However, the adhesive often does not last long and the tape should be replaced on a regular basis to avoid residue left on the platen.

can be thrown in the garbage or flushed down the sink.  The short answer is “No” to both disposal options. - See more at: http://impressions.issshows.com/screen-printing-process/Proper-Ink-Disposal-Methods-8219.shtml#sthash.2xaisdDG.dpuf

Can waste ink be thrown in the garbage or flushed down the sink? 

The short answer is “No” to both disposal options, but the proper answer is "maybe"... if the ink is properly filtered or cured. Regardless of if you’re using plastisol or water-based inks, you must remember that they contain industrial chemicals, the disposal of which is strictly regulated. In all cases, you should familiarize yourself with local, state and federal regulations.

Plastisol inks are 100% solids. When fully cured, the PVC resin fully absorbs the plasticizers in the ink to form a plastic ink film. Some municipalities may allow fully cured plastisol inks to be disposed or recycled as regular plastic waste in the municipal waste system. Uncured plastisol may be eligible for recycling. If not, it likely will need to be disposed by an authorized chemical waste disposer. If you send your plastisol waste for disposal, ask whether it is eligible for incineration, which completely destroys the waste and, thus, reduces the potential for cleanup liability in later years.

Despite their name, water-based inks aren’t water, nor are they necessarily environmentally friendly or benign. They should not be poured down a sink or into the ground, or thrown in the garbage. They contain various binders and pigments, and may contain solvents, such as formaldehyde or alcohols. Some of these ingredients are considered hazardous. Your local laws may allow you to reduce disposal volumes by opening the lids and allowing the water (and any solvents) to evaporate off.  The remaining pigmented binder should then be disposed of in accordance with local regulations.

When disposing of ink containers, ensure they are completely empty. Empty metal drums should be sent to a drum reconditioner for reuse. Empty cardboard drums should be completely empty and disposed of according to manufacturers’ and regulatory requirements. If you use liners in the cardboard drums, the drums can be crushed and thrown away as municipal waste. Empty plastic containers can and should be recycled. If you plan to reuse plastic pails to store or handle liquids, be aware that they can pose a drowning hazard to small kids.

Please remember that improper chemical disposal is a criminal offense and guilty parties (employees, managers and owners) have served jail time and paid large fines. Local municipalities are aggressive in tracking and pursuing offenders, so take the time to research and comply with your local municipal waste laws. 
can be thrown in the garbage or flushed down the sink.  The short answer is “No” to both disposal options. - See more at: http://impressions.issshows.com/screen-printing-process/Proper-Ink-Disposal-Methods-8219.shtml#sthash.2xaisdDG.dpuf




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Davis International
388 Mason Road
Suite 1A
Fairport, NY 14450
Phone: 585-421-8175
Fax: 585-421-8707