The wooden stock of the roller is first covered with a double thickness of woollen material—flannel or Melton cloth—and over this is drawn the cover of calf-skin, flesh side outwards. The manipulation of the seam must be managed with extreme care, as any unevenness would render the roller useless. At both ends of the cylinder the leather projects, and is usually drawn tight with string or nailed on. There are two descriptions of leather rollers—smooth and coarse. The latter are only used to apply ink to the stone or plate, and then, with the smooth roller, the proper distribution of the ink is effected. For the latter purpose, in collotype, hard glue or indiarubber rollers are employed, being considered far preferable. When a leather roller _is_ in good order, and its use has been thoroughly mastered, it is looked upon by many printers as indispensable. A serious disadvantage is that when new they are almost unusable for collotype, and after prolonged use the leather stretches, they become wrinkled, and this, of course, affects the even distribution of the ink. A new leather roller needs a special preparation or “breaking in” before it may be considered fit for use. It should be well saturated with a fatty matter, a very effectual way of doing which is to roll it well at intervals in a moderate supply of thin varnish as used for thinning printing ink, this process being persevered with so long as the roller continues capable of absorption. A better but more troublesome method is to roll the rollers twice daily in thin varnish, continuing the operation for a week, at the end of which time the roller may be well rolled upon the inking slab in stiff black printing ink, the superfluous ink being occasionally removed from both the roller and slab by scraping with a blunt knife, and a fresh supply of ink applied. This troublesome and tedious operation should be continued for a period extending over several weeks until it has become quite smooth and even, though it will still be found better to use it only for common work, or, if possible, on stone. To keep the roller in good condition it should, on each occasion after use, be carefully scraped with a clean, smooth-edged knife—not too sharp. Some practice in this operation is required to avoid cutting the leather. Great care should be taken to avoid this, the blade of the knife being held almost flat upon the roller during the process. The scraping should always be in one direction, to ensure which it is advisable to place a mark upon one of the handles. Unless these precautions be observed the ink will dry in, and completely spoil the leather. If not to be used again for some time tallow should be carefully and thoroughly rubbed into the surface of the roller as a preservative, but before again using this coating must be removed either by means of a knife or washing with turpentine.