Using Pumice on Your Glass

Volcanic Rock is Your Friend

Pumice can be a very versatile abrasive for use with glass. Unlike loose abrasives like silicon carbide or aluminum oxide, pumice is a friable abrasive that allows you to achieve a fine surface grind on your glass.

It can be used to give a pre-polish finish on your glass from a fine grit surface or even achieve a near polish without using cerium. Pumice can be used with a brush wheel or MJ wheel on a lathe, it can be used by hand with a Scotch-Brite pad, it can be used with a cork belt on an upright belt sander, and it can be used with a felt pad or cork pad on a flat lap grinder as well.

It's a highly versatile abrasive that can be utilized with virtually every type of cold-working equipment.

Safety First

Just like any other loose abrasive you may use in your coldworking shop, like silicon carbide or aluminum oxide, Pumice can very quickly become airborne in your coldworking use and create a cloud of the abrasive in the air while mixing or using the pumice.

It is essential to follow safety shop rules when using abrasives like pumice. Never work with pumice without using a respirator or vacuum filtration system. Be sure to clean your work area at the end of the day and not leave piles of pumice around on your equipment or workspace that can become airborne later.

Pumice sits between loose abrasives like silicon carbide and cerium in its abrasive quality on your glass and in how it is mixed and used with water.

While silicon carbide is used with water to create a loose slurry for grinding your glass and cerium is used with water to make an almost liquid slurry for use with felt to polish your glass, pumice is mixed with water to form a nearly mud-like consistency to finish your glass surfaces. It's much finer than silicon carbide, so it will blend with the water, but not as fine as cerium, so it needs less viscosity to work well on your glass surfaces.

Making Mud Pies

Brush Up on Abrasive Grinding

One of the more common ways to use pumice is with a brush wheel on a lathe.

The brush wheel allows you to get into hard-to-reach areas of your cast work to polish and clean up the surfaces without removing the distinctiveness of the piece. The rows of cactus fiber brush move in and around your piece while moving the pumice across the glass to abrade and clean the surface area gently.

Brush wheels and pumice are a great way to quickly and efficiently accomplish finish work on your complex shapes.

Hand Control

Along with using a brush wheel or MJ wheel on a lathe, pumice can also be used on a cork belt, a felt pad on a flat lap, or even by hand with a Scotch-Brite pad.

For pieces that require more precise control, you can easily mix pumice and use a Scotch-Brite pad to gently abrade and work the surface of your glass into a lustrous glow.