Do you know where the sweet spot is on your flash dryer? Every flash unit has an area that gives off the most consistent heat. How do you find out where that is? Print expert Colin Huggins has a solution: creating a heat map using puff ink. Let’s find out how he does it.
THE “SWEET SPOT”
No matter how large your flash dryer is, there’s a sweet spot. This is where the dryer heats the strongest and most consistently. Usually, this is in the center of the flash unit. That makes sense, right? The center is always the warmest place to be, as less heat is being lost to outside elements. Think of it like a penguin huddle: the warmest penguins are the ones in the middle.
Differently sized flash units have different-sized sweet spots. Riley Hopkins Flash Dryers have an infrared heating element constructed with tight wire construction, reducing the possibility of having hot and cold spots. However, it’s important to get to know your flash unit so you can identify the sweet spot and stay in it when flashing or curing garments.
Pro Tip: Make sure to align the size of your platens and flash dryer. If your flash dryer is larger than your platen, the sweet spot will be larger. If the flash unit is smaller than the platen, the sweet spot will be that much smaller, no matter what you do.
Always warm up your flash dryer and platens for testing. You’ll get the best representation of how flashing or curing will go in a production run.
HOT VS. COLD PLATENS
Warming the platens is important for many reasons. It keeps the ink flowing smoothly and makes flash times more consistent and even. If you flash a print with cold platens, the ink may not gel at the same rate. You can end up curing some spots while others stay wet.
Before you get printing, warm the platens. Turn on the flash dryer, let it warm, and then swivel it over the platen until it’s warmed to about 100°F-120°F. Use a laser temperature gun or a donut probe to get a surface reading of the platen. To double-check that the platen is ready for printing, touch the bottom of the platen with your hand. If it’s warm all the way through, you’re ready to go.
Pro Tip: The longer you print, the hotter your platens will get. Once platens reach 140°-150°F, adjust your flash times to accommodate for a hotter platen. Wood platens will take longer to reach this temperature all the way through.
Warm platens help prints gel more efficiently because heat is radiating from the bottom up as well as from the flash dryer. If you want to test exactly where heat from the flash unit is dropping first, do a heat map test with a cold platen. Since there won’t be any heat coming from below, you’ll get an accurate reading of where the exact sweet spot is on your flash dryer.
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Platens are warm and the flash unit is turned on. Let’s get this test rolling. The most obvious ink to show off a heat map? FN-INK™ Puff.
USING FN-INK™ PUFF TO CREATE A HEAT MAP
FN-INK™ Puff is a low-cure plastisol puff additive. It activates at about 200°F, cures at 260°F, and is stable until 280°F-290°F. After that, the puff collapses. It’s the perfect way to do a heat map test: you’ll be able to see exactly which areas puffed properly.
To get started, burn a screen with a large rectangle design. The rectangle should be as big as you can make it; about ½” from the outside of your platens. Make it as large as possible to get the best heat map results. Use a low mesh count to lay down a thicker deposit. You’ll be able to see more puff in the test.
Mix FN-INK™ Puff into your favorite low-cure plastisol ink. Use the inks you’d regularly use in a job. Don’t use metallic inks like FN-INK™ Metallic Gold or Silver, as these reflect heat and take a little longer to flash. To get the most loft, mix puff at 20% by weight. If you’re doing a 100-gram sample, add 80 grams of color and 20 grams of Puff.
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Flood the screen, then do a couple of consistent print strokes. Send the newly-printed heat map under the warm flash dryer and keep an eye on it. Once you see puffing, pull the platen out from under the flash dryer.
Try not to over-puff the ink. If FN-INK™ Puff gets too hot, it will collapse. This won’t ruin your heat map, but it won’t be as helpful as perfectly-puffed ink. Use a laser temperature gun or donut probe to keep tabs on the surface temperature of the ink. If you warmed up the platens, getting a perfect flash in the center of the sweet spot shouldn’t take long.
HEAT MAP TEST RESULTS
Once the ink has cooled a bit, check the heat map. What did you notice? Did the edges of the rectangle puff as much as the center? Are the edges of the rectangle still wet? Generally, the sweet spot in a flash dryer is in the center. The area where the puff ink is activated is the sweet spot. If the design stretches almost all the way to the edge of the platen, the ink at the edges may not be fully gelled. As your flash dryer and platens reach production temperatures, the heat will be distributed more evenly.
If the sweet spot from your flash dryer is smaller than the majority of designs you print, it’s time for a bigger flash. However, an inconsistent gel may not be entirely your flash dryer’s fault.
RELATED: HOW TO PROPERLY CURE PLASTISOL INK WITH A FLASH DRYER
OTHER FACTORS
When flashing or curing with a flash dryer, it’s important to make sure everything is warm before you start to flash. As mentioned before, warm platens and a warm flash will make for a more consistent gel or cure.
Another factor that can cause inconsistent ink gelling is airflow. When using a flash dryer, try to limit airflow as much as possible. Close doors and windows on windy days and turn off fans to get the best flash possible. Even walking by the flash unit with a stack of shirts can cause airflow. A little bit of airflow is okay, but your environment should be relatively still.
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If these factors have been addressed, you’ll have a great heat map that represents how your flash dryer is behaving.
Heat mapping is a great way to establish the sweet spot in your flash dryer. Using FN-INK™ Puff gives a crystal-clear picture of which parts of the flash are curing faster. Make sure to take notes so you can get a perfect gel later, and keep testing to get to know your flash dryer.
