Polishing rock slabs removes imperfections from the flat surface of the rock. You can polish rock slabs to make items, such as bookends, tabletops or even kitchen counter tops. Hand polishing, however, takes a good amount of time and effort, so if you want to polish your own rocks, be prepared for the physical and time strains that come with it.
Things You'll Need
Bucket of water
Plate glass (optional)
3 sheets 80-grit sandpaper
3 sheets 150-grit sandpaper
3 sheets 320-grit sandpaper
3 sheets 400-grit sandpaper
3 sheets 500-grit sandpaper
3 sheets 600-grit sandpaper
Dip your cloth rag in the bucket of water. Squeeze as much water from the rag as possible. With your rock slab in your lap, wet the surface of the rock slab with your damp rag. If the rock slab is too heavy to place on your lap, lay plate glass on your floor and gently place the rock slab on top of the glass.
Sand the rock slab using your 80-grit sandpaper, until no pieces of the rock jut out. This may take up to 30 minutes for course rock slabs.
Sand the rock using your 150-grit sandpaper. Wipe down the rock slab with the damp cloth.
Sand the rock slab using your 320-grit sandpaper. Proceed for 15 minutes. Wipe down the rock slab with the damp cloth.
Sand the rock slab using your 400-grit sandpaper. Proceed for 15 minutes. Wipe down the rock slab with the damp cloth.
Sand the rock slab using your 500-grit sandpaper. Proceed for 15 minutes. Wipe down the rock slab with the damp cloth.
Sand the rock slab using your 600-grit sandpaper. Proceed until perfectly smooth. Wipe down the rock slab with the damp cloth.
Place the rock slab on your felt mat. Apply the polishing compound according to the manufacturer's instructions.
With each different sandpaper grit, try to remove as many imperfections as possible. If, at any point, you notice that the sandpaper grit is too fine to remove remaining imperfections, use the lowest sandpaper grit to sand the rock. To determine when to change to a finer (higher number) grit, use a pencil to draw a crosshatch on the rock slab and sand for a few minutes. If the crosshatch completely disappears, then you can move to a finer grit.
Remove every bit of grit (powder) from the rock slab before moving to a finer-grit sandpaper.
Only use a polishing compound appropriate for the type of rock that you polish. The University of Oregon Department of Physics website suggests using a tin oxide for hard rocks and cerium oxide for soft rocks.
Always exercise caution when working with heavy rock slabs, glass and polishing compounds. Where appropriate safety equipment, including rubber gloves, safety goggles and a face mask.