Rollers should not be washed immediately after use, but should be put away with the ink on them, as it protects the surface from the action of the air. When washed and exposed to the atmosphere for any length of time, they become dry and skinny. They should be washed about half an hour before using them. In cleaning a _new_ roller, a little oil rubbed over it will loosen the ink: and it should be scraped clean with the back of a case-knife. It should be cleaned in this way for about one week, when _ley_ may be used. New rollers are often spoiled by washing them too soon with ley. Benzine may be substituted for oil; but, owing to its combustible nature, it is objectionable, as disastrous accidents have ensued from its use. Mr. Hansard, an eminent English printer, says, “Take glue, made from the cuttings of parchment or vellum, fine green molasses, pure as from the sugar-refiners, and a small quantity of the substance called Paris-white, and you will have every ingredient requisite for good composition. The proportion as follows:— Glue, 2 lbs. Molasses, 6 lbs. Paris-white, ½ lb. Put the glue in a little water for a few hours to soak; pour off the liquid; put the glue over the fire, and when it is dissolved add the molasses, and let them be well incorporated together for at least an hour; then, with a very fine sieve, mix the Paris-white, frequently stirring the composition. In another hour, or less, it will be fit to pour into the mould.” Various patented compositions for rollers may now be had from type-founders. COVERING TYMPANS. Tympans are generally covered with parchment, which should be of an even thickness, and about two inches and a half wider and three inches longer than the tympans. Tympans have been sometimes covered with linen, which, on account of its evenness, would answer the purpose; but it is so apt to stretch, that the tympans become slack in a short time, and bag (as it is termed), and thus slur the impression. Silk is excellent for fine work.