Rock polishing is a lapidary process whereby rough stone is polished and smoothed by hand or using simple machines to produce attractive stones. The most common means is tumble polishing, but there is also vibratory finishing.
To effectively polish rocks in a tumbler the rocks must all be of the same approximate hardness. Rocks are placed into a tumbling barrel with with varying degrees of abrasive grit or and water. Depending on the hardness of the rocks each step in the tumbling process can take place over a number of days.
Rocks start out as something called a "tumbling rough" this is an untreated stone. A tumbling rough is placed into a tumbling barrel with with abrasive grit and water, this initial procedure is called the Coarse Grind. The purpose of the Coarse Grind is to wear down any sharp or uneven edges on the rocks surface, eventually producing smooth round stones.
The second stage of rock polishing is the Fine Grind, this is the same as the Coarse grind differing only in the use of a finer grit and that the stones are no longer shaped but are beginning to be polished. at the end of this step the rocks should appear shiny when wet, but mat when dry.
The Prepolish step uses a mixture of very fine grit and plastic tumbling pellets. At the end of the proses the stones have a slight luster when dry.
The final two steps are the Polish and in some cases the Burnishing. In the Polishing step rock polish is added in place of grit as well as the plastic tumbling pellets. After further tumbling the rocks should now have a shiny look when dry. If this is not the case and the Rocks appear to have a film on them one can try Burnishing.
In Burnishing the rocks are tumbled with only the plastic pellets and the addition of an oil free non abrasive soap.
Famous quotes containing the words polishing and/or rock:
“As polishing expresses the vein in marble, and grain in wood, so music brings out what of heroic lurks anywhere. The hero is the sole patron of music.”
—Henry David Thoreau (18171862)
“The forest waves, the morning breaks,
The pastures sleep, ripple the lakes,
Leaves twinkle, flowers like persons be
And life pulsates in rock or tree.”
—Ralph Waldo Emerson (18031882)