The texture of a slumping mold is far superior when kiln wash is sprayed on. There are no brush strokes and kiln wash doesn't pool into all of the mold's nooks and crannies. After firing, the backs of your slumps will be incredibly smooth.
Use the kiln wash sprayer
that's available on our site. Fill the paint sprayer with your kiln wash mix. Add some decently sized marbles. Find an area in your studio that is enclosed on all but the front side. I have a shelf nook made out of melamine that I've hung a shower curtain in front of. You could use a sturdy large cardboard box, or construct a plywood box covered in shelf liner. (A cardboard box has a limited life). Cut an appropriately sized hole in the top of your construct to plug a shop vac hose into.
Make sure the plug is tight. Use duct tape to fill in any gaps. Your vacuum should have a HEPA filter approved for particulate matter. This filter will need to be cleaned every few months, depending on use, and will need to be replaced once every year or so.
You are now ready to spray. Put on your mask. Make sure your mold is clean. Prop your mold up so the surface is facing you. Turn on the vacuum. Shake the paint sprayer until the marbles are moving around freely. The marbles will help to keep your kiln wash integrated with the water. Point the sprayer at the top right-hand side of the mold and start spraying, moving at a steady pace from right to left. Shake the sprayer continuously. Apply 2-3 coats or when the kiln wash reaches the appropriate color. If the kiln wash is running down your mold, you've sprayed too much. Your mold should look evenly coated with a smooth finish. In my studio, we use these slumping molds a dozen times or more before we need to reapply wash for most molds.
If you are spraying casting molds for full fusing, double your application and you will probably need to respray each time.
We don't recommend spraying kiln shelves. It's very time-consuming to get enough coverage.