Last time we explored some ways to cure certain challenging garments. Here are some more tips to ensure a proper cure, no matter the substrate!
When many screen printing veterans first got started, they may not have realized just how many variables factored into properly curing their prints. As the industry has advanced, new technology has made it even more difficult to get fully caught up. Fortunately, by familiarizing yourself with the basics of curing and doing some careful tests, you can make it easier to get a proper cure.
The Right Tool for the Job
Over the years, you’ve probably heard stories of (or know personally) screen printers who cured their shirts in the kitchen oven, burned out mom’s favorite iron, used their flash cure for full cures, or purchased a heat gun (designed for baking and stripping paint) from a local hardware store. Maybe you’ve tried one of those ideas yourself! If so, it probably didn’t take you long to realize your production was suffering. While there are plenty of creative ways to cure screen printed garments, a conveyor dryer is the only real solution for a professional screen printing shop.
Some Basics of Curing
There are no long-term shortcuts to a conveyor dryer if you want to produce quality prints in any kind of financially viable quantity. Finding a dryer that will fit your workspace and your workflow is the first step, but how can you be sure you’re using it to get the best cure possible? Knowing the basics and doing some testing is a good way to start.
The right technique for curing your prints depends on the type of ink you’re using. The two basic types of ink used for screen printing are plastisol and water-based ink.. Here are some general guidelines for successfully curing them:
- Plastisol ink – The industry standard, known for its opacity and durability. Most plastisol inks cure at 320° F (some as low as 280° F). Check the technical data sheet from the manufacturer for each plastisol ink for complete instructions.
- Water-based ink – Known for a soft hand and color, these inks use water as a solvent to carry the pigment. Water-based inks require evaporation to properly cure, so they need longer dwell times (from 90 seconds to several minutes) with curing temperatures from 300° F to 360° F. With the addition of additives, some claims are as low as 200° F to 280° F. Once again, check the manufacturer’s technical sheet and recommendations and, time permitting, test and record your results.
Testing the Cure
Even if you’ve followed your ink manufacturer’s recommendations to the letter, there are so many variables in the screen-printing process that the only way to guarantee the quality of your print is to test it. A “wash test” is usually considered the best method to ensure your apparel is properly cured and that your dryer is functioning properly. Many screen printers will do a wash test before starting a big order, or if the order is for any type of garment you think might present curing issues (like special effect, textured, metallic or gel inks). Just run the test garment through the laundry like you regularly would. If the print stays on and has no noticeable defects after it’s been washed, it has passed the wash test. It’s that simple!
If the ink wasn’t properly cured, some of the print will wash off; the amount the print has degraded after washing will give you an idea of how insufficient the cure was. Some manufacturers suggest waiting 24 to 48 hours after printing before conducting a wash test for maximum accuracy. While it’s impossible to entirely prevent deterioration from occurring, you need to determine if the cure is within acceptable tolerances before sending it to the customer. In addition to providing some important quality control, periodically washing test shirts helps you see if your dryer is working properly – it’s a bit of preventive maintenance that could equal big savings later.
A “stretch test” is another popular curing test – probably because it costs nothing and can be done repeatedly over the course of a print run. Typically you’ll stretch the print around one half the total stretch of the t-shirt. If the print doesn’t crack and retains its shape when the fabric is relaxed, the ink is most likely cured. If your ink cracks or fails to return to its original shape, the ink is probably undercured.
Some Other Issues to Watch Out For
In regards to curing screen printing ink, much of the focus today is on curing at the lowest possible temperature. With the advent of new synthetic/organic blends, issues like bleeding (dye migration, or dye gasses trapped under the ink diffusing into the ink and discoloring it) have drawn more attention than ever. Additional issues like ghosting (a soft halo around the print), see-through (parts of the image unintentionally being visible on both sides of a shirt), and shrinkage/scorching have led screen printers to seek inks that cure at lower temperatures. It’s important to record and maintain the dryer settings you use to achieve successful curing for different inks and fabrics; detailed records will make it easier for you to get the best possible cure for future jobs.
With all the variables you’ll encounter in the printing process, getting a proper cure can seem like a pretty daunting task. But with a reliable conveyor dryer, a solid understanding of basic curing requirements and some careful testing and attention to detail, your screen prints will look great and stand the test of time. And most important, they’ll keep your customers happy!