Often overlooked, one of the most important aspect of screen printing is the curing process of the ink. Ink a tricky substance to deal with and if not properly handled and cured, the print will fade and crackle after the wash, or normal wear and tear.
There are many different types of inks and each has a unique way of curing. Our choice of ink is plastisol ink. Plastisol ink is pretty much just melted plastic along with some other substances which is in a liquid form at room temperature.
Water based inks can generally just air dry, because the water evaporates from ink evaporates from the surface of the shirts leaving the ink to dry up on the fibers. On the other hand, plastisol inks cure/dry much differently. In order for plastisol inks to dry it must be heated to about 325 degrees Fahrenheit. This doesn’t mean that the oven or dryer that she shirt is being cured in must be 325 degrees, rather that the actual plastisol ink on the shirt must reach 325 degrees.
At around the temperature of 200 degrees the ink comes to a state which the surface is dry, but is still not bonded with the fibers; this is called the semi-cure state. Once the ink reaches 325 degrees it chemically fuzes with the fibers on the shirts (almost as if it becomes one with the fibers) and becomes “cured”. It’s crucial that the whole surface of Ink on every layer that is printed reaches the cure temperature (325 degrees). This can be done by slowing down the belt speed of the dryer and/or raising the temperature of the dryer. Our dryer is set to a speed of 5.5 and a temperature of 1025 degrees; it seems to work for us.
If ink is not properly cured it can crack, fade or wash off. This is obviously not what you want as a screen printer, so here are some easy ways to check if the ink is cured. The method that I like and the easiest method is by using a temperature gun. This gun measures the surface temperature of the shirt and should read between 325-350 degrees. You point the gun at the ink on the shirt as it is coming out of the dryer. The other way to check is fairly simple, it’s called a stretch test. What you do is try and stretch the shirt and see how much of the ink cracks. Ultimately you want to make sure that cracks stay to a minimum. The last and best way to check is by throwing the shirts in the wash. If the ink doesn’t come off you did it right. Now go ahead and start printing custom t-shirts!
If you are interested in getting some custom t-shirts in Brooklyn New York or anywhere in the U.S. don’t hesitate to ask us!