Things You'll Need
24 inches of one-by-four scrap lumber
Hand-held grinder with 30 to 60 grit pads
Polishing brick (12 grit or less)
Coarse sandpaper (optional)
Slate has a dull porous look and feel, and many homeowners are attracted to its natural matte-like finish. But when you apply slate to the edge of a step or a platform, you might not like the rough-cut edges. You don't want to polish the edges as you would with marble, as this would look too glossy. Even a wet saw can leave the slate edges looking too smooth when compared to the surface. It takes some skill to artfully match the edge texture with the surface texture.
Place a piece of slate tile on the workbench with the edge facing you. Clamp the slate between scrap lumber and the workbench. Set the grinder speed to a low setting and use coarse pads.
Gently grind the slate edges with a hand-held grinder. Bevel the top edge at a 45-degree angle, or a rounded edge or no angle at all, depending on your preference. Keep the grinder moving in slow arcs. Grind until the shape is as desired. Do not over-polish.
Hold the polishing brick at the desired angle along the edge facing you. Gently polish, beveling the top edge slightly if desired. Keep moving the brick in circles. Do not dig too deep into the soft slate. Repeat using slightly finer grit sandpaper if necessary. You are finished when the edge texture matches the surface texture.
If you want a rougher finish, skip the hand-held grinder and go straight to the polishing brick. You can bevel or shape the edge of the slate with a grinder and profiler tool. See the video link provided in References for more information. (This video about marble also applies to slate–just work slower and more gently with the softer slate material.) You will then have to roughen the texture with a polishing brick or coarse sandpaper.
Always wear safety goggles, gloves and a dust respirator when cutting or polishing slate or stone.