Okay, so you’re ready to give up screen printing because, for the last couple of times, your screens came our underexpose and the emulsion dripped away during washout, or it over-exposed and you can barely see through your screen. You are pissed because you followed the instructions to the T, and you’re feeling frustrated for having to waste all that emulsion and time. Well, you are not alone and fortunately, the process of exposing is easier than you think.
Whether you’re in the tropics of Thailand with high humidity or in dry and nippy Switzerland, forget what the manufacturer has recommended, often times they aren’t setup like how we are. Note: I use a flood light with a 500kw halogen bulb at 2.5 feet from my screen. Just bear in mind, in whatever setup you have, make sure to maintain the distance between the light source and screen at all times, else your calculations won’t be accurate.
Grab a cardboard (or something solid so no light will pass), and cut it into 6 strips with even dimensions. Line them up over your screen and make sure you don’t leave any space in between each strip. Letting light pass through will mess it up.
You can use see-through tape to lightly hold down the strips in place. You should have something like the picture below. Now, get your stopwatch. Flip on the light switch, and begin the exposure.
Start removing each strip as it hits your adjusted time. I go by intervals of 2 minutes.
Okay, I hope you see the point of doing now. After you’re done, take the screen to the washout booth and you’ll start to notice at which interval your image is exposing correctly. If you’re just starting out, don’t get too ambitious with an image that has a ton of details. Start with a solid image with large areas for exposure – do the calculations a few more times to pinpoint your optimum exposure time, then move on to finer images from here. Don’t worry, you’ll get it. Good luck!