Durable stencils are incredibly important to the integrity of your print. A strong stencil is required for all printing however it is especially important when you have a long print run or are printing with water-based inks. During long print runs the emulsion can wear down causing your print edges to be less crisp. Today we discuss when to use post exposure and how you can use post exposure to strengthen your emulsion.
What is post exposure?
First let’s do a small recap on the processing of exposing emulsion, understanding this process will help you to understand how post exposure works. Exposing emulsion is when the emulsion coated onto a screen-printing frame is exposed to light, the light hardens the emulsion anywhere the light touches the screen. The hardened emulsion on the screen does not rinse out, what remains is your stencil.
Post exposure is exposing the screen again to light after the screen has already been exposed rinsed and dried. The purpose is to strengthen or to help harden any remaining soft emulsion.
Should you post expose your screen and when should you use this technique
You should strengthen your stencil using post exposure when you have a long print run (over 100 t shirts.) During long print runs emulsion can wear down from the ink and squeegee. Post exposing will strengthen your stencil and it will be nice and crispy for the duration of your long print. You should also post expose your screen if you aren’t using a water-resistant emulsion with water-based ink. Water-based ink will wear down emulsion quick if you are aren’t using an emulsion formulated to be water resistant.
Note: We do not recommend using water-based inks unless you are using an emulsion formulated for this ink type.
How to Post Expose your Screen
The technique of post-exposure is quite easy. As usual, the screen needs to be exposed, rinsed, and given time to completely dry. Depending on the thickness of your emulsion layer, return the stencil to the exposure unit for one or two minutes for a speedy post-exposure.
Note: Time will vary on post exposure depending on how long you exposed your screen the first time.
If you are looking to make your screen absolutely bulletproof, we recommend using emulsion hardener. When using this product, it will be nearly impossible to reclaim the screen. Emulsion Hardener should be used if you want to keep the frame for future use. For example, a client orders the same t shirts from your quarterly. If you save this screen, you won’t have to burn a new screen each time and the emulsion hardener will keep the stencil nice and crisp each time you print.
