Going Over the Basics: Coating and Exposing Screens
Coating and exposing a screen perfectly is not an easy task. In our latest video, we've pulled together a few of viewers' favorites from previous deep dives into the darkroom processes. The quick reference will provide best practices for drying clean screens, how to properly coat emulsion to a screen, and what to look out for when washing out the screen.
DRYING CLEAN SCREENS
After cleaning a screen, your goal is to drain any leftover water from the screen. A few methods exist for drying screens properly.
One way is to put screens on a screen rack. The screens shouldn't sit flat because the water can puddle on the screens (and if you rinsed out the screens with hard or soft water, the minerals can collect on the screen which will cause issues when applying emulsion). Grab something you have around your shop like a 2x2 or a stack of cleanup cards to slightly prop the rack at an angle. Place a fan behind the rack to blow air directly across the screens. It is a good idea to place an HVAC filter behind the fan to prevent dust and lint from sticking to the screens.
Putting a dehumidifier in your darkroom/place where you dry screens is also helpful because the goal is to move warm, dry air in the space to enhance the drying process. You'll need that dry, warm air not only for drying clean screens, but for drying coated screens as well.
COATING SCREENS WITH EMULSION
The angle and pressure applied when coating a screen with emulsion matters. You could put more pressure on the back of the scoop coater, which allows the coater to cut more emulsion. Or you could put more pressure on the front of the coater, which influences how much emulsion is cut and how much goes through the screen.
Many different methods for coating screens exist. They all work, as long as you meet the end goal, seeing the glistening effect. The glistening effect is when the coated screen reflects the light; it doesn't look dull at all. The glistening effect signifies that the emulsion is on top, bottom, and in-between the threads of the screen. Having the emulsion wrapped around the threads is important because that's how the emulsion holds onto the screen.
EXPOSING A SCREEN
Let's talk about vacuum exposure units compared to compression exposure units. Vacuum exposure units will always give the tighter contact between the film and screen. That close contact means when the light hits the film and screen, there are little to no chances for the light to wrap around the edges, causing soft and fuzzy edges on the stencil. If you have a compression lid exposure unit, it's best to put as much weight as you can on top of the cushion to increase the contact between the film and the screen.
WASHING OUT THE SCREEN
When you're washing out the screen on the squeegee side, you don't want to use any sort of pressure. Remember, the emulsion is thinner on the squeegee side, so you don't want to blast any of your details out. On the shirt side, you may use a pressure washer, but do not get too close because you may wash out some of the image or emulsion.
Every shop will have a different darkroom process. Play around, test it out, see what works best for you. If you want to learn more about the darkroom, check out our past videos.