It's easy to think of your screen printing press as the backbone of your operation. But remember, a press can only deliver quality prints if it's printing through quality screens.
Your screens deserve as much attention as any other part of your setup, because no amount of printing technique will save a job from a poorly prepared or maintained screen.
Keep Your Screen Printing Screens Squeaky Clean
Before you get started prepping your screens, keep in mind that they're not all created equal. A new screen shouldn't be cared for the same as a used screen. When you get a brand new screen straight from your supplier, it might be tempting to think it's ready for emulsion. How could a screen fresh from the factory be dirty? That screen still had to be handled by people during packing and shipping, and besides the oils from human hands, it could've picked up troublesome dust and dirt along the way. It's important not to assume a screen is clean just because it hasn't been used - this can cause headaches further along in the process, like pinholes - imperfections in the stencil caused by contamination or poor preparation.
Anatol's washout booth is the perfect place
to get your screens clean and ready to go.
Let's get that new screen ready for ink! In order to make it good to go, we need to really get that screen clean. Degreasing should take care of any pesky oil and dirt that can affect your emulsion. Start by rinsing both sides of your screen with water, with a pressure washer if you have one. Spray your degreasing chemical on each side of the screen, scrub and rinse thoroughly to remove all the degreaser.
Just because you've degreased your screen doesn't mean you've totally removed the possibility of contamination. You've also got to be careful how you dry your screens. Having a clean place to store screens while they dry is key to ensuring quality stencils. A horizontal rack kept in a place free from dust and debris or a dedicated drying cabinet is a good place to let your screens dry. If your dry screens have been sitting around for awhile, check that they haven't collected debris that could be harmful to your stencil.
When you're preparing your screens for printing, be sure to choose your shop's cleanest possible location. An air purifier can help remove any potential contaminants from your work space and keep your stencils looking sharp.
Preparing Your Emulsion
Now that your screens are thoroughly clean and dry, it's time to prepare your emulsion. Keep in mind that your emulsion preparation and coating should be done in a room free from UV light to avoid premature exposure. You're not out of the woods when it comes to pinholes just yet. Sometimes, the way you prepare the emulsion itself can lead to imperfections in your stencil.
If you're using a diazo emulsion - a two-part photosensitive solution that requires mixing in either a powdered or liquid sensitizer - first make sure you mix the sensitizer thoroughly. Let it sit for awhile to give any air bubbles a chance to dissipate; air bubbles can cause problems with your stencil if applied to the screen. When you add the sensitizer to the emulsion, make sure you mix the two completely and let it sit again to allow air bubbles to settle.
When you coat your screen with emulsion, completely fill the holes in the screen mesh. Remember that anywhere without emulsion won't harden into a stencil and will allow ink to pass through onto your shirt - the only open spaces on the screen should be your design!
Exposing Your Screens
Once you've coated your screens with emulsion, let them dry completely in a UV-free room before exposing them. It's tempting to use warm air to help them dry quicker, but be careful not to introduce contaminants that could ruin the stencil. When your screens are dry, it's time to head over to your screen printing exposure unit.
Anatol's Aurora UV LED exposure unit will help
you expose your screens quickly and efficiently.
Before exposure, make sure the glass of your exposure unit is free of debris. Place the positives of your artwork between the light source and the screen and expose the screen for the amount of time recommended by your emulsion manufacturer. A lot of variables go into finding the perfect exposure time, so it helps to have an exposure calculator. For more tips on exposing your screens just right, check out our blog post:
Cleanliness is Key
If you couldn't tell by now, the "big secret" to avoiding pinholes is cleanliness. Keeping dust and dirt out of your screen preparation area will go a long way towards producing consistently good stencils. Keep every item involved in the screen making process free of debris, from your exposure unit to your film positives. If you take extra care to keep your work area clean, you can save yourself a lot of flawed prints and headaches.