How To Coat A Screen With Emulsion

Posted by Ronnie Cannon - Outside Sales on 7/7/2013

Screen Coating is also referred to as "making a stencil". This is done with an emulsion. Emulsion is a thick liquid that is sensitive to UV light. When it dries it forms a photographic type of film. When the art work is placed on the photo sensitive emulsion, and exposed to a UV light source, it creates a negative stencil of the art as the emulsion behind the artwork is protected from exposure to the UV light source. The negative stencil will allow the ink to be printed on the garment in whatever color you choose. This print will be a replication of the film positive. Emulsions are biodegradable.

There are three types of emulsion: dual cure emulsion, diazo emulsion and the fast exposing pure photo polymer emulsion. There is also UDC-Ace for water-base and solvent based inks. All emulsions work with plastisol inks. Mix and store according to manufacture's directions.

Use of a Scoop Coater is recommended when applying Emulsion to your screen


Coating The Screen

   A. Pour the scoop coater full of emulsion.
   B. Secure the screen frame in an upright position, preferably so that you can use two hands to hold the coater. This can be accomplished on a small table with a block of wood between the screen and the wall to keep the screen from touching. If this is not feasible, you can hold the frame with the one hand and the coater with the other.
   C. Press the rounded edge of the coater tight against the bottom of the print side of the mesh and tilt the coater forward until the flat left and right edges of the coater touch the mesh.
   D. With some pressure, drag the coater up the mesh slowly until you reach the last inch or so at the top. If you move the scoop coated up the screen too fast you will risk introducing air bubbles into the emulsion which may lead to premature breakdown during the printing process.
   E. When coating screens emulsion needs to be even on mesh. Thick and thin places will cause problems during drying and exposing.
   F. Thin places will expose faster causing image to not wash out from over exposure.
   G. Thick place will expose slower causing image to break down and wash out.
   H. After coating dry in a clean rack. A good tip is coat screens before going home for the day and let dry over night.
   I. Screens need to be dry to the touch before exposing.
   J. While drying screens put into screen rack with print side down and a dehumidifier or dry box helps screen dry faster.
   K. Humidity can cause major problems because stencil needs to dry completely on screen mesh. A dehumidifier will help with the problem.

An alternative to coating a screen is to use Capillary Film or the low cost EZ-Film.

3 Types of Coating Methods:

1 & 1 Coat - Apply one coat of emulsion on print side, rotate 180º once on the squeegee side. Dry emulsion in horizontal position.
2 & 2 Coat - Coat twice on printing side, then twice on the squeegee side, wet on wet. After each coat rotate screen 180º. Dry screen print side down. This will require longer dry time, longer exposure time, thicker stencil - good for athletic printing.
3 & 3 Coat - Use method 2 above, after complete drying in method 2, add an additional coat on print side, and dry again. This produces the sharpest edges and thickest stencil and ink deposit.
3. Pre-registering the screen: To minimize the press set up it is recommended that you pre-register the art to the screen before you expose it.