Learn How To Screen Print With Catspit Productions, LLC
Using Direct Emulsions: Screen Coating Tips
It is always best to start with the highest quality direct emulsion for the best performance. Make sure to choose your emulsion properly for your printing application. Understanding emulsion characteristics will help you do that with beneficial results.
When coating screens manually it is often difficult to achieve a smooth uniform surface with consistent thickness. To ensure complete coverage, filling in all of the mesh openings, you will want to use a multiple pass method with 2 passes being the minimum. Scoop coaters come with a thin, sharp edge and a duller, round edge. The thin, sharp edge will leave less emulsion in the mesh where the round edge will leave more emulsion in the mesh.
Some screen coating tips to remember:Only coat your screens under red or yellow safelight conditions.
Mix your emulsion well before dispensing it into your scoop coater.
A scoop coater should be clean and its edges free of dents and nicks. A smooth edge is best.
Make sure the scoop coater is well filled. You don't want to run out of emulsion halfway up the screen.
Once the scoop coater is filled, the emulsion should be applied immediately. Emulsion left sitting in the open is a target for dust and debris.
In low humidity environments, an open container of emulsion can begin to form a skin quickly, so keep your emulsion in an air tight container until you need it and after you apply it wash out your scoop coater right away.
Once the emulsion makes contact with the mesh, proceed slowly. Emulsion is viscous, and it needs time to fill the mesh openings. Use a slow smooth passing action to move the scoop coater up the screen. Moving too fast can trap air bubbles in the emulsion and when they pop, the mesh can remain open creating pinholes.
Coat the substrate side of the screen first. Begin your coating pass at the bottom of the screen. Firmly support your screen as you press the edge of the scoop coater against the mesh. Move slowly up the screen and slow down to a stop near the top. Twist the scoop coater upwards and off of the mesh. Flip the screen quickly and repeat on the ink well side.
If you want a thicker stencil, use more passes for each side always ending with the ink well side. If a thinner stencil is desired, then use less passes, again always ending with the ink well side. This forces the emulsion through to the substrate side. This is where the stencil must extend above the threads of the mesh in order to achieve a good emulsion over mesh rating.
When drying your screens, make sure to place them substrate side down and in a rack that is parallel to the ground. This allows gravity to pull the emulsion toward the substrate side resulting in better stencil thickness. The screens should be allowed to dry in the dark and worked with in safelight conditions only.
Direct emulsions must be dried completely before being exposed. Any dampness in the emulsion during exposure will interfere with the chemical reaction that takes place in order to cure the emulsion. This could also create a poor stencil and result in a screen that is difficult or perhaps impossible to reclaim. Allow your screens to dry slowly and make sure there is ample air circulation to allow moisture to dissipate away from the drying screens.
For extra thick stencils it is possible to coat a screen and allow it to dry. Then the substrate side may be coated again to fill in imperfections in the emulsion surface and gain some minimal thickness. The thinner, sharp edge of your scoop coater will be ideal for this technique.
Always be sure to use fresh emulsion and work in a clean, dirt free environment. Proper mesh preparations are also necessary to ensure excellent emulsion performance. Try to learn about your particular emulsion's characteristics. Knowing this information will help you achieve the results you desire.