Glass can be given a jewel-like shine and smoothness by grinding and polishing. Both grinding and polishing glass involves the scraping or wearing away of uneven patches and scratches by friction. Grinding involves the use of large, coarse particles of hard material for shaping or removing large surface imperfections. Polishing uses particles of very small size and of softer materials to remove finer surface imperfections. Grinding and polishing not only smooths and shines glass, it also improves the fit of mating pieces and helps to shape glass into sculptures.
Abrasive Cloths and Papers
The most basic tools used for grinding and polishing glass are abrasive cloths and papers. These are cloths or papers with mineral grit of varying degrees of fineness bonded to them with resin. Silicon carbide and aluminum oxide are the two most common abrasives used in such cloths.
Abrasive paper is also formed into belts and used in belt sanders. These grind and polish much faster than by using elbow grease alone. Belt sanders are powered devices.
Rouge is sometimes used for polishing glass. Rouge is made of iron oxide (rust) mixed with various organic materials to form a waxy block. Cloths are dipped in the rouge and then used for fine polishing of glass surfaces. It can be difficult to obtain, as it is suspected to be carcinogenic. However, you can purchase a substitute made with cerium oxide.
Hand-held stones are used for grinding. They are not natural stones but instead are grinding grit held into a stone shape with resinous adhesives. Use all the surfaces of the grinding stone at the same rate to prevent it from becoming uneven and grinding poorly.
Grinding wheels or discs are powered metal discs to which grinding agents such as powdered diamond have been affixed with adhesives. Some are electrically driven. However, as grinding wheels build up heat quickly and sometimes use water for cooling, electric power is not always safe for these devices. For this reason, many grinding wheels are pneumatically powered.
An Electrolytic In-process Dressing system (ELID system) is used most often in industrial glass polishing, where high-quality surfaces are needed. An ELID system is a powered abrasive disc with nano-sized grit. An electrode is fixed next to the grinding wheel, and an electrolytic solution is pumped between them. Electric power is supplied to the whole system. This system not only allows for superfine polishing but also prevents the grinding wheel from becoming clogged with glazed glass, a problem that can plague simple grinding wheels.