=Glue Rollers= have long been in use, but chiefly for letterpress work and steam machines in general. A soft composition of a very elastic nature is quite useless for collotype; its substance must, on the contrary, be tolerably hard, and of a brown colour, as usually employed on the steam letterpress jobbing machines. For hand rollers for collotype it is preferable to have a strong iron frame with double handles, as used by letterpress printers. Such rollers are preferable to those of leather, and will answer perfectly for laying on the first stiff ink, and also for rolling up the half-tones. To clean they should on no account be scraped, but simply washed with turpentine, and on this account are much easier cleaned than leather rollers. Schaarwächter gives the following as an excellent composition for collotype rollers: Brown glue, three parts, steeped for two days in cold water. The pieces should then be dried in a cloth, and afterwards dissolved. When melted add, with constant stirring, one part of treacle, which has been previously boiled, allow the whole to boil, and skim. The composition is then run into a thin copper cylinder or mould, which must be polished smooth, clean, and well oiled; and in the centre of which has been placed the wooden cylinder or stock. After cooling, the roller is pushed out of the mould, and washed with alcohol or turpentine to remove any trace of greasiness due to oiling the mould, placed in a bath of tannic acid, washed with water, and dried. The composition rollers, as used in typographic printing, are made with glycerine instead of treacle, and may be used for collotype if not too soft. =Indiarubber Rollers= are more expensive, but possess special properties rendering them particularly suitable for photo-lithography. In construction a wooden stock with suitable handles is covered with very thick well-vulcanised indiarubber, which has a fine smooth surface, rendering it easy to clean by means of turpentine. If it becomes “tacky” on the surface it should be well rubbed with French chalk, or soap-stone, which will readily absorb the turpentine, but this coating must be thoroughly removed before again using the roller. An excellent suggestion appeared in one of the polytechnical periodicals, that the rollers should before use be coated with a solution of pure or bottle rubber in benzole or bisulphide of carbon after having been well washed with turpentine.