Decant
American Watchmaker and Jeweler (1892)
To pour off a liquid from its sediment; as the decanting of diamond powder, prepared chalk, etc. Saunier advises the watchmaker to prepare all his smoothing and polishing materials by decantation, as he will by this means free them from hard or large particles and obtain a uniform grain. At the present time the watchmaker can, however, obtain diamond dust, prepared chalk, etc., ready for use, that are supposed to have been properly decanted. There are, however, many poor concoctions that have not gone through the proper treatment, and if the watchmaker is desirous of doing fine work and having reliable materials always at hand, it is well to decant these preparations, even though they be labeled "prepared." The operation is a very simple one and takes but little time. The material, being reduced to a powder, is placed in a vessel filled with water, oil, or other liquids, according to the nature of the material to be operated upon, and after being thoroughly stirred it is allowed to partially settle. The liquid is then poured into another vessel, the heavy portion remaining in the bottom of the first vessel. This residue is only fit for use in the very coarsest work. The liquid is then stirred, allowed to settle partially again and is then poured into another vessel. The powder left should be labeled I. By successive operations, each time increasing the interval of time allowed for settlement, finer deposits can be obtained, which may be labeled respectively, 2, 3, 4, etc. In decanting diamond power or oil-stone dust, oil should be used; for tripoli, rottenstone, or chalk, water; and for hartshorn and some other materials, alcohol is used. Diamond powder, as purchased from the material dealer, can rarely be improved upon by manipulation unless the operator is expert.
What Has Changed in the Last Century
When the American Watchmaker and Jeweler gave this advice in 1892, a watchmaker who wanted a uniform grain had to grade his own abrasives by settling them in water, oil or alcohol, and the writer warned that shop-bought "prepared" powders were often poor concoctions. Abrasive powders are now sorted industrially by air classification and centrifugal sizing and sold in graded micron sizes /, 3, 1, even a quarter of a micron in diamond paste / so the bench-top sequence of jars labelled 1, 2, 3, 4 has almost entirely disappeared from the trade. The physics is unaltered: settling velocity still depends on particle size, and the same principle underlies laboratory sedimentation analysis. Claudius Saunier, cited here simply as "Saunier", is still read / his Treatise on Modern Horology remains in print as a reprint for restorers of antique watches.
Written for this edition, 2026.