No matter how long you have been in the sublimation business, variables change all the time and sometimes overnight. A heat press may suddenly not heat up to the temperature it shows or apply even pressure even though it has worked for two years without an issue. An item may be slightly changed in manufacturing, requiring a heat and time adjustment, which usually happens without warning, or it could be a brand new item you have never used before.
Luckily, you don’t need a ton of extra items to do testing. All blanks can be pressed multiple times for testing purposes. Anything that is previously sublimated will fade out, but the coating itself can take on multiple presses and will not be affected. The easiest way to test is with small black strips—a black box image printed in RGB mode at full black—to assure that it’s transferring the truest color (maybe throw in a few primary colors). Then press those onto the substrate and make sure it’s the right result. Black looks brown when over-pressed and grey when under pressed, so that is a pretty good way to figure out what combination of temperature, time and pressure produce the deepest black with sharpest edges. It is generally bad practice to test a full image on a final item and just hope it works right off the bat. That often leads to a wasted item with no extra white space that can be re-used for testing.
Once the perfect black is achieved with the right combination of settings, we recommend printing out an RGB color chart and pressing that onto the item(s) that will be big sellers. That way, you will know exactly what the colors will look like on the final product. Remember that light can produce more color combinations (what you see on screen) than what a physical pigment can create (what you see on the final product).
—Kalina Mondzholovska, Coastal Business Supplies