The balls must be perfectly free from grease.

English mechanic and world of science. 66.3 December 1897

Snooker.—A copy of the only number in print containing the recipe has been sent; but if the billiard balls are of ivory, they can be stained well enough for all practical purposes by soaking in the aniline dyes of the desired tint, taking the precaution to wash them quite clean first. For black, the usual method is to clean, dip (soak) in a neutral solution of nitrate of silver, and then into a weak solution of sulphide of ammonium; for red, make an infusion of cochineal in liquor ammonite, and immerse the balls in that, after having “quicked’’ them by soaking for a few minutes in a solution made just acid to the taste by the addition of aquafortis (nitric acid); but in each case the balls must be perfectly free from grease.