An Appropriate Finish for Slate

Wood finishes won't work well with stone. Instead, use a stone sealer. June 10, 2006

I recently made a coffee table with slate tiles set into the top. I sprayed the whole thing with Krystal lacquer. The lacquer has started to come off the slate. Does anyone have any suggestions? Should I remove the lacquer on the slate and finish with a poly?

Forum Responses
(Finishing Forum)
From contributor R:
I think your finish is coming off due to some contamination on the surface of the slate. Remove the existing finish. Then clean with a detergent wash followed with a mineral spirits wipe. Then apply a blonde de-waxed shellac as a sealer which will ensure that whatever film finish you apply will stick well and not peel. Do you really need to add protection to tile or maybe you just need a tile sealer?

From contributor C:
Most stone finishes are dilute acrylics which will soak deeply into the stone (others are silicone based). I do not know of any oil based finishes that are recommended for use on stone surfaces. Add to that the dusty flaky nature of most slates and you have a recipe for failure. When you choose lacquer (which is very brittle and has some adhesion issues anyway) you have assured yourself of a very difficult path. Really now the proper way to do this is to purchase a properly chosen stone sealer/finish.

From the original questioner:
Yes, I knew when I did it that I might be looking for trouble. I was up against a deadline and it looked good when it left the shop. I will look into stone sealers.

From contributor M:
Yes, Krystal is a superb wood finish, but obviously not for slate. Call around to tile suppliers. I have a good friend locally that owns a tile store that has a beautiful slate fountain in the middle of the showroom that's been coated with whatever brand stone sealer he carries. Don't expect the stone sealer to be the most durable thing in the world, as I don't think most of them are cross-linking finishes like Krystal. They can't be or else they'd be too brittle on stone, as you've found out.