How to Properly Cure Plastisol Ink with a Flash Dryer

A flash dryer is a versatile piece of equipment and can be used in many ways, no matter how small your shop is. Curing with a flash dryer takes a little bit of experience to dial in, but can be another way to cure prints without a conveyor dryer. In the video, Josh Wells walks you through properly curing garments with a flash dryer. 

WHAT YOU’LL NEED

Curing with a flash unit isn’t perfect, but you can get the job done with practice and the right tools. 

First, you’ll need something to measure the temperature of your ink as it cures. You can use a temp gun or a donut probe to check the temperature of your ink. Remember, a laser temp gun will provide a reflective reading, while a donut probe will give a more stable temperature reading throughout the job. However, a donut probe is more expensive, and may be out of your budget. Curious about the differences? Check out this blog to get the full scoop. 

You’ll also want to use the proper size flash unit for the job you’re doing. For most jobs, a 16x16 or 18x18 flash will fit the bill. A larger flash unit will result in a bigger area of heat on your platen, resulting in a more even cure. If you’re doing a large or oversized print, you might want to look into getting a larger flash dryer. 

Since full cure is only achieved when the entire ink layer reaches cure temperature, having the right tools will help you get the job done right. Josh uses FN-INK™ for this job, which cures at 260°F. 

DIAL IN YOUR SHOP

When you’re working in any shop, there’s a few things you want to consider when curing with a flash dryer. 

First, you want the space you’re working in to be warm, between 70-80 degrees. This applies to everything in your shop. If the ink is cold, it won’t be as creamy and easy to print with, shirts will cool down quickly and be harder to cure, and so on. By keeping your shop warm, you can eliminate potential issues before they happen. 

RELATED: HOW TO PREP PLASTISOL INK FOR SCREEN PRINTING

Air flow is also an important factor to consider when curing with a flash. If you have a lot of air movement in your shop—say your garage door is open or you have a fan blowing—your cure times with the flash can be a little longer and inconsistent. Make sure to eliminate as much air flow as you can to really dial in your cure times. 

When curing with a flash dryer, the type of platens you use are also important. Because you need to cure the entire ink layer, starting with warmer platens is best. Wood platens will warp over time when you heat them up quickly too often. Aluminum platens won’t warp over time. Josh uses aluminum platens on the press, but wood platens are more budget-friendly. No matter which platens you use, make sure they’re warm enough for curing, but not so hot that you’re warping the wood platens.

RELATED: THE DIFFERENCE BETWEEN WOOD AND ALUMINUM PLATENS

If you have a one-station screen printing press, you can’t rotate print stations between curing shirts. To avoid warping your platens with the constant heat from a flash dryer, set up a separate curing station next to your press. That way, you can print, take the shirt off the platen, set it on your curing station, and rotate the flash over it without worrying about getting those platens too hot. 

Now that everything is ready, let’s talk about the logistics of curing plastisol ink with a flash dryer. 

CURING WITH A FLASH

To cure with a flash dryer, first you need to make sure your flash is up to temp. This usually takes about 10-15 minutes. If you’ve been printing already, your flash should be good to go. Again, make sure your platens are warm as well. 

Usually, a flash unit sits about 2-3 inches above the platen. The closer your flash is to the ink, the faster it will cure. Be careful though, too close and you could scorch the garment. Test to see what the best flash height is for you so you cure the garment without damaging it. 

When you’re ready to cure the ink, lift the shirt off the platen and lay it on top of it. If the shirt is still stuck to the platen, there’s no space for the heat to penetrate through the garment. By setting the shirt on top of the platen, you’re giving the air underneath the print a chance to heat up through the ink layer and help to cure it from top to bottom. 

Now swivel the flash over the shirt. Remember, you’ll need the entire ink layer to get to 260°F or above. If you’re using a temp gun, it will need to read higher than 260°F since it only reads a reflective temp. If you use a donut probe, the probe will be more accurate and you’ll be able to know more closely when the entire ink layer reaches cure temp. Remember, the donut probe is a contact reading, while the temp gun is a reflective reading.

Keep the platen under the flash dryer until your ink layer is fully cured. This is usually around 30-40 seconds. Remember, the more powerful your flash is and the closer your flash is to the shirt, the faster it will cure the ink or potentially scorch your garment. Test before going into production.

RELATED: ENSURING PROPER INK CURING

TEST FOR FULL CURE

After your ink has reached cure temperature, let it cool down. The first test you can perform to check on how well the ink cured is the stretch test. 

Once your ink is cool, try stretching it a little bit. Don't pull too hard on it, or you can split the ink layer. Most shirts won’t go through a lot of strenuous stretching, so you don’t need to pull too hard. Try to imagine what the person wearing this shirt will be doing while wearing it, and stretch it accordingly during the test. 

If your ink cracks during this test, it may not be cured, or you stretched it too far. Ink that looks like cracked, dry earth means it isn’t cured properly. You’ll need to flash the next shirt a bit longer to reach full cure. If it looks more like an even split, you’ve stretched it too far.

Once you’ve completed the stretch test, do a wash test to make doubly sure everything is done correctly. Send your garment through the washer 3-5 times and inspect it each time.

Keep testing until you’re satisfied with the end result. Then, make a note of the cure time and other variables so you can be consistent in production.

Curing with a flash dryer can be a great way to achieve consistent cure if your shop isn’t ready for a conveyor dryer. With a little patience and practice, you’ll be able to cure garments in a flash.