Coating the screen can sometimes be a tricky process. Uneven coating, bubbles, old emulsion, etc can all lead to terrible results later on. This tutorial will focus on getting a smooth, even coating on your screen using direct emulsion.
Direct emulsion consists of diazo-cure, dual-cure or pure photopolymer emulsions. Direct emulsion comes in the form of a liquid substance (it typically smells like glue when you open the container). Most emulsions will require mixing of a sensitizer with the contents of the container to activate the emulsion. Once the emulsion is properly mixed, let it stand for an hour or two to let any bubbles settle (these can cause uneven coating results). A scoop coater is used to spread the emulsion onto the framed screen. The mesh must be dry for emulsion to properly adhere.
Step 1 – Place a piece of wood or 2 x 4 against a wall (I use my closet door). Make sure you are coating the screens in a light safe area (using yellow bulbs) or at least in a dark room away from direct sunlight. I always use newspaper to cover the general area as emulsion can get really messy.
Step 2 – Prop the screen frame up against the the piece of wood so it is stable. You will be applying pressure with the scoop coater and you do not want it to slip during the process. Also, make sure you have properly degreased and dried the screen.
Step 3 – This is another angle of the set up. Get your scoop coater ready once you open the emulsion.
Step 4 – Pour the emulsion into the scoop coater. Don’t worry about pouring too much in there because you can always pour unused emulsion back into the container when finished.
Step 5 – Most scoop coaters have a thin and thick edge. Make sure the sharper (thinner) edge of the scoop coater is facing the screen. Tilt the scoop coater flat against the screen across the mesh until the emulsion contacts the screen.
Step 6 – With an even motion, slide the scoop coater up the screen to deposit a thin layer of emulsion. Remember to keep it flat against the screen until you reach the top. As you start to reach the top, tilt the scoop coater away from the screen.
Step 7 – Depending on the type of emulsion you use, you may need to coat the inside of the screen frame as well. I always do one coat on both sides.
Step 8 - Typically, the sides will have thicker drips of emulsion. I will use a small piece of card stock to even out the edges. After this step place the coated screen in a well-ventilated, dust free area that is completely dark (no light at all!). Make sure to lay the screen horizontally to promote even thickness as the emulsion dries. To speed up the drying process you can use a fan.
Step 9 - Pour any remaining emulsion back into the bucket and close the container. Clean it all up and wait for the screen(s) to dry!