How to Polish Slate

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posted on 13 years ago — updated on 1 second ago

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Slate is a fine-grained material used on roofs, as tile, or in furniture. Because it is composed of tiny minerals, such as quartz and hematite, slate often gives off an attractive sparkle. While you can polish slate, the result can be slippery and more difficult to clean. Consider regular cleaning and buffing as a simpler alternative.

Steps

Cleaning the Slate

Strip away dirty wax if necessary. If the slate is covered in a layer of discolored or cracking wax, this needs to go before you can clean and polish it. Select a commercial floor stripper appropriate for stone and dilute with water according to label. Mop this over the floor and let dry, then rinse if directed by the label. Floor strippers are powerful chemicals. Protect yourself with goggles, rubber gloves, and excellent ventilation.

Clear away dirt and debris. Sweep the slate using a soft broom. If you are handling slate tiles, make sure you remove all debris from the grout. You may use a vacuum cleaner instead, but only with a soft brush attachment. Handling the vacuum too vigorously may chip the slate.

Clean the slate with soapy water (optional). If your slate looks dirty or streaky, clean it before you start polishing. In most cases, mopping with warm water and plenty of soap will be enough to remove the dirt. Rinse thoroughly to remove soap suds, then let dry until the slate looks dull and uniform.

Remove stubborn stains. If you clean the slate twice and still see grime, move on to stronger cleaners. An alkaline (high pH) cleaner such as ammonia-based glass cleaner or natural stone cleaner is your best bet for slate. If that doesn't work, rinse it off and try a mild acidic cleaner. Your best option is an alkaline commercial cleaner from a home improvement store, specifically for slate or at least for natural stone. Test all cleaners on a corner first. Acid can discolor some types of slate. Alkaline cleaners are less likely to cause damage, but this is not guaranteed.

Buffing to a Smooth Surface

Wet the stone. Wet the slate thoroughly. Buffing while dry may cause further scratches.

Buff with wet 200 grit abrasive. Buy 200 grit diamond pad or wet & dry sandpaper from a hardware store. Wet the abrasive, then rub it gently over scratched areas until the scratches are less visible.

Rinse all materials. Rinse off the slate and the abrasive to ensure that no dust remains to cause further scratches.

Repeat with 400 grit abrasive. Move on to a 400 grit sanding surface. Once again, wet the slate and the abrasive, then start buffing. Rub it over a wider area this time to ensure a more uniform look.

Rinse again. Wash the dust off thoroughly from all materials.

Finish with 600 grit abrasive. Wet the slate and the 600 grit abrasive. Buff over the entire slate surface. Continue rubbing until the scratches are no longer visible. Rinse thoroughly when finished.

Creating a Glossy Surface

Consider linseed oil. A small amount of linseed oil will create a dark shine on the stone without causing damage. However, oil attracts dirt and makes the slate harder to clean. For this reason, oil is not recommended for floors or outdoor surfaces.

Learn the pros and cons of sealer. Stone sealer can create as glossy a surface as you like, but can make it very slippery, especially when wet. If the slate is outdoors or in an unheated room, water can seep under the sealer and crack off the sealer when it freezes and thaws. Slate can be honed (smooth) or rough (with small jagged edges). Sealer is more effective on honed slate.

Apply the sealer. If you do decide to apply a sealer, find one specifically designed for slate or at least natural stone, preferably a penetrating sealer for long-lasting protection. Apply a thin layer with a paintbrush, following the grain of the slate. Let dry for two hours (or as the label recommends), and reapply as necessary. Test the sealer on a corner to ensure it results in the desired gloss/matte, slip resistance, and color.