Just like baking a cake, drying a screen requires that you follow a specific recipe.
By Mick Orr
Have you ever baked a cake? It's easy! Just rip open a box of cake mix, dump it into a bowl, add some water, an egg, and some oil, then stir it around a bit, pour it into a cake pan, and bake it for 40 min at 325°F. A piece of cake, so to speak.
As long as you follow directions, the cake is likely to turn out fine--not too dry and not too moist. Say you're in a hurry, though, so you try to speed up the process. Instead of following the directions, you decide to spread the batter out over a cookie sheet and bake it at 650°F for only 20 min. You don't have to be a pastry chef to know what will happen. In no time, you will have the fire department visiting you, and not for cake and coffee.
Drying a screen is not unlike baking a cake. Screen drying is a basic prepress step that seems like a no-brainer on the surface. But because it appears so simple, many printers tend to gloss over the factors that lead to a correctly dried screen. Consider the following scenarios:
1. A screen-printing business operates in a small crowded shop. Screens are made in a bathroom converted for the purpose. Coating occurs with the bathroom's fluorescent lights turned off, because everyone knows that light will expose the emulsion. Still, the screenmaker needs to see what he's doing, so the bathroom door is left slightly ajar to allow a small amount of light into the room. When the room is used for other purposes, coated screens are stored in the bathtub (which also serves as the developing and screen washout/reclaiming area). The shower curtain has been replaced with a piece of black plastic to protect the screens from light exposure when they are in the tub.
For coating, a coating trough with a smooth, nick-free edge is used to apply freshly mixed dual-cure emulsion onto properly stretched screens. After coating, screens are leaned against the side of the tub with a fan blowing on them. The trusty old fan has been used for years, and a thick layer of dust coats the blades. If time is short, a hair dryer is typically used to speed up the drying process. Screens are usually made as they are needed and rarely stored after coating.
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