Q:

What’s the difference between working with tile and slate? Can I cut slate with a snap cutter, or am I better off using my wet saw?

James V. Ryan, Putnam Valley, NY

A:

Jane Aeon, a tilesetter in Berkeley, California, replies: Uniformity of thickness is one big difference. Gauged slate has uniform thickness; ungauged slate can vary from 1/4 in. to 3/4 in. thick. Surface dimensions also can vary by up to 1/4 in.

The most important difference is that some slates need to be sealed before they are worked with. I installed slate a few years ago that was so sensitive, my handprints showed on the surface. I had to remove the first few slates and seal the rest before setting.

Slates with rough surfaces should be sealed before grouting, or you’ll need a scrub brush and grout remover to clean the residue from the surface of the stone. Ask your supplier for specific instructions on what type of sealer to use and when to apply it to the slate.

To answer your second question, I have yet to find a snap cutter that could snap slate. You should use a wet saw instead, but be careful: Dense materials such as slate can’t be cut as quickly as soft ceramic tiles can be. You have to push the saw more slowly and use a porcelain-tile blade.

When you’re setting slate, be sure to back-butter the tiles (make sure there’s no dust on the back) with a good latex-modified thinset.