Chapter 2 Materials and Equipment

Cerium, a metallic element, the oxide of which was discovered in 1803, was named for the asteroid Ceres, which had been found two years earlier.

The oxide (CeO2) is pale pink in color, has none of the messiness of rouge, and polishes two to three times as fast; many optical workers have recently used it in place of rouge.

Some cerium oxide samples, on being sifted between the fingers, seem to contain rather coarse particles, but evidently in slow hand polishing, as on mirrors, these lumps disintegrate without doing any harm, as extensive trials have failed to produce a single scratch. In machine polishing, which is entirely different, cerium oxide does sometimes scratch, and the finer Barnesite is used for the finish polishing.

Barnesite (trade name), brown in color, is compounded of the oxides of several of the rare earths. It is finer than cerium, is perhaps as rapid in its action, and probably yields the most superior polish of all three products.

For a further discussion of polishing agents, refer to the section, Theory of Polishing, in Chapter V.

Obviously, in purchasing grinding and polishing agents directly from manufacturers, somewhat larger quantities than those given here will have to be ordered. It may be more economical to obtain the small quantities needed from a local optical shop, if it will sell them, but bring along your own containers as a precaution against mixing the grades. The small jars with screw covers which druggists use for ointments are excellent. Always dispose of any grade which should chance to become contaminated with a coarser one.

For the lap, about one pound of pitch should be obtained, as well as half a pound of rosin, and about two ounces of beeswax. Most optical pitch is a refined pine-tar product, a viscous fluid
which, when cold, assumes a solid shape but flows under pressure. It usually has to be tempered with rosin or turpentine. Rosin, beeswax, and sometimes a satisfactory grade of pitch can be obtained from a paint or hardware store. Pitch of doubtful purity, after being melted, should be strained through cheesecloth.

Sources of supply for these materials are: carborundum, Carborundum Co., Niagara Falls, N. Y.; alundum, Norton Co., Worcester, Mass.; emery and rouge, American Optical Co., Southbridge,

Mass.; Bausch & Lomb Optical Co., Rochester, N. Y., also supplies
a fine grade of rouge. All of the abrasives and polishing agents
listed, as well as pitch and other accessory materials, can also be
obtained from the Universal Shellac and Supply Co., 401 Broadway,
New York 13, N. Y.

Kits that should contain suitable quantities of the necessary materials can be bought from some supply houses. Miscellaneous items: Also needed are a water pail; a water bottle or shaker, such as a cruet (or a tin can with a perforated
cover); a coarse and a fine carborundum stone; turpentine; paraffin; a small paint brush from the 5 & 10 for applying the rouge; and a magnifying lens about 1" to 1½" m focal length. Also a small pot; empty cans for melting the pitch, beeswax, and paraffin; and an electric hot plate or gas burner.

To be made or improvised are: a template; a channeling tool; grinding stand or barrel; testing rack for the mirror; Foucault testing device; and stands to support the last two items.

The template