Ryonet | #PoweringThePrint
Screen printing heat transfers can seem daunting but in reality, it’s fairly simple. If made properly, plastisol heat transfers can last almost as long as a screen prints and can be much easier to apply in certain scenarios. Here are a few ways screen printing your own transfers can help your business:
I know, I know. Tons of reasons for heat transfers clearly exist. How do you go about it? What would you need? Let's walk through the basic components and process of screen printing your own heat transfers.
How do screen printed heat transfers work? A plastisol heat transfer can be screen printed with standard plastisol ink or a special plastisol ink specifically designed for screen printing transfers. If you are not solely screen printing transfers you can use your standard plastisol ink. The ink is printed in reverse (reverse image) onto a heat transfer paper that has a special coating on it which will release the ink once heat pressed. After the last ink color is printed, an adhesive powder is sprinkled onto the wet ink (this is what helps the transfer to adhere to the shirt during heat pressing). The ink is then gelled — but not cured. To gel an ink is to get it to a stable, dry state where the ink can't be smudged if accidentally bumped against something. Once gelled, the transfer can be heat pressed onto a garment at any time.
Insider's Tip: Heat transfers can have a shelf life. The shelf life is directly tied into how “dry” or “gelled” the ink is. Over time some of the oils and liquids in the transfer can be soaked up by the transfer paper, this will look like an oil stain or halo around the transfer. When you notice this on your transfer, it is no longer usable.
When making a screen for printing transfers, you want to coat the screen with a slightly thicker coat of emulsion then you would typically coat for printing directly onto a garment. Use the round side of the scoop coater in order to achieve a thicker coat of emulsion on the screen. You want a thicker ink deposit on the transfer paper; therefore, you need a thicker coat of emulsion.
DON'T FORGET: When printing films, you want to reverse the image when you go into the print dialog. When exposing the screen, your image will be in reverse and it will show up correctly on the shirt once it is reversed again during the heat pressing process.
Screen printing a heat transfer is pretty straightforward. You need to set a standard off-contact of 1/16″ and ensure this off-contact is consistent throughout the screen. If you are printing only a few transfers you can use a small amount of spray adhesive to hold the transfer in place. If you plan on printing a lot of heat transfers or multiple color transfers, we recommend that you look into a vacuum pallet that holds the transfer down with suction during printing. For printing multiple color transfers, you do need to print in reverse print order (under base last) and carefully flash between colors. How long you flash each color is dependent on the details in the design. If the design has thick areas, it needs more time to gel. Say you're making a neck label that has fine print, the thin area will gel very quickly.
To print, you can use a standard 70 durometer squeegee. We would recommend using a thicker, opaque ink because it will hold up better during the transfer process versus a thin ink that is transparent. We recommend using either Wilflex™ Top Score Ink or FN-INK™.
After printing the ink, apply Transfer Adhesion Powder over the wet ink. You can do this by spreading out the adhesion powder in a big bin and just dipping the transfer paper into the bin, coating it with the powder. Once the ink has been covered with the adhesion powder, pick up the paper and shake off the powder. Be sure to tap the paper several times to get all the powder off the paper (except where it sticks to the ink, of course).
Insider's Tip: If you do not tap ALL the powder off of the paper, the adhesion powder will increase the likelihood of the paper sticking to the garment.
Actually, you are not really curing the ink during this step. You want to GEL the ink so when you heat press it later, the heat from the press will fully cure the ink. How long it takes to gel the ink and what temperature it needs to reach depends on the type of ink you're using and the level of detail within the print. Remember, thicker designs need more time while thinner designs need less time. Low cure inks like FN-INK™ and Wilflex Top Score will need less heat whereas typical plastisol inks (ones with 300°-320° cure temps) will need more heat.
Printers usually keep the ink under the heat for 6-10 seconds, but that can change due to the ink layer thickness and level of detail in the print. For low cure inks like FN-INK™, you'll want the ink to reach 180°. For inks that cure at 300°-320°, you'll want the ink to reach around 240°. For that reason, do not use different kinds of ink for a multicolor transfer. Pick an ink cure temp, and stick with it.
How do you tell if your ink is properly gelled and not under- or over-gelled? A perfectly gelled ink should peel from the paper. If the ink is under-gelled, the ink will be flaky. If the ink is over-gelled, it will feel like a solid sheet, making it difficult to remove from the transfer paper. You'll know if the ink has gelled perfectly if it has some stretch. The ink should also split easily, but not chip or break.
Once you transfer is cured — oh wait, I mean gelled — you should store it in a dry, temperature-controlled area. If stored properly, it can last for more than a year.
The easiest part! We recommend setting your heat press to about 30°-40° hotter than the stated cure temperature. If the ink cures at 260° or 270° (the cure temps for FN-INK™ and Top Score), set your heat press to 290°-300°. For standard plastisol inks, set between 330°-350° and heat pressing it for 10-12 seconds with a medium pressure. A medium pressure means that you should press firmly down onto the press when applying transfer to the garment. Once you have reached the time limit, peel the paper off immediately for hot peel or let the transfer cool for cold peel. Always perform a wash test to confirm it reached proper cure and has great adhesion.
IMPORTANT TO KNOW: If you let a hot peel transfer sit too long (you must peel immediately) the paper will not come off. If you don’t wait long enough to remove a cold peel transfer, you’ll have the same problem. We prefer using the Transal Premium HOT PEEL because we usually peel the paper a second or two after it comes off the press and it works painlessly.
Always test and dial in your process before you go into production. Since everyone uses different types of ink, each printer will be facing various curing temperatures, which means different gel temps. You'll have to play around with your flash units, conveyor dryers, heat presses, and printing methods to discover what works best for you.