Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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embossing

1. The process of raising a surface pattern on leather by means of engraved cylinders or plates, generally employing both heat and pressure. The patterns produced are often simulations of the grain patterns of some animal skins but may also be unrelated to any natural pattern. One roller or plate, in which the design is engraved, is made of steel, while the other, having a softer surface, is made of cotton or papier-mâché. The leather is embossed by passing it over a heated, steel cylinder, thermostatically controlled at a pre-set temperature, or in a press, of which there are two basic types: one in which the pressure is applied by a roller mounted on a moving carriage, and another in which pressure is applied to the platen by mechanical or hydraulic means, but without any lateral movement. In both cases the leather is pressed against a heated plate which is either smooth and polished so that the leather is ironed, or engraved to impart an artificial grain pattern. While the latter type of press is designed to employ heavier pressures, the first type is superior in that the movement of the roller causes a small amount of slip, which imparts a more lively character to the leather. On the other hand, the advantage of the mechanical or hydraulic press is that it can dwell at full pressure, which is desirable for producing deep effects in some embossing processes.

It is important that the design embossed in the leather be as permanent as possible. In this regard both the structure of the skin and the type of tannage are important. A very full and tight structure is required. Calfskin gives the ideal structure for the finer leathers and cowhide for the coarser. Vegetable tannage is far superior to chrome because it builds up the fibers to a much greater extent and makes the structure correspondingly tighter.

Embossing of leather is sometimes (and perhaps frequently) a means of simulating the grain pattern of a superior leather on an inferior and/or less expensive skin. An example of this would be a calfskin embossed in imitation of MOROCCO .

2. The process of imparting a raised or depressed design in paper: 1) by passing the paper between an engraved steel roll or plate and another roll or plate of a soft or compressible material, such as paper or cotton; 2) by pressing the paper between strong, coarse fabrics; or 3) by passing the paper between etched male and female iron or steel rolls. The operation is used to create decorative effects and is generally applied to book, blotting, or cover papers. Plate or spot embossing is a method by which individual designs, as distinguished from all-over patterns, are embossed. This technique is accomplished by means of vertical presses, the paper being embossed by placing it between the embossing die and the counter or make-ready of the press and forcing it into the intaglio areas of the die.

3. To impress the marks of ownership into a page of a book by means of a device employing a sunken die and a raised counterpart which raises the design above the paper. See also: PERFORATING . (2) 4. To block the title, author, or other bibliographical information, on the cover of a book. See also: BLOCKING (1) . 5. See: BLIND BLOCKING . (94 , 189 , 233 , 234 , 264 )




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