WHY DOESN'T MY IMAGE WASH OUT?
Doesn't stay in the mesh
Emulsion is easy. If the stencil washes out - it wasn't exposed with enough UV-A energy, the sensitizer is not crosslinked and the stencil dissolves with water and rinses down the drain - just like it is supposed to.
Image area doesn't wash out
If the image area doesn't dissolve and rinse down the drain, the sensitizer was somehow crosslinked with heat or UV-A energy. This usually means your positive failed to stop UV energy from reaching the stencil like a bad umbrella.
We often get calls from people that wash outside or actually apply the positive outside, and aren't thinking about the tremendous invisible UV energy of the sun.
Dime Complete Opacity Test
To judge if your positive completely stops UV energy, tape a dime, different thicknesses of wire or a piece of aluminum foil to the stencil and after exposure compare how the area covered by the dime washes out compared to the dark areas of your positive.
If the area covered by the dime doesn't wash out, you have exposed the stencil to UV energy or heat energy before you exposed with a positive 'crusted' the stencil.
POSITIVE FAILURE
Test to make sure the emulsion actually will dissolve
- Wash fresh stencil with no exposure
Crust - A little bit of exposure, but not enough penetration to cross-link the entire thickness.