Emery is an abrasive made from granulated garnet used in the production of stone lithograph plates to polish the plate surface.
It is a pale brown mineral compound consisting of silicate, which contains magnesium, iron, manganese, calcium, etc. Although larger stones are made into jewelry and used as decorative stones, emery is mostly utilized as an abrasive because it is hard and relatively inexpensive for a mineral. It is often used as the abrasive coating on sandpaper and for sandblasting patterns onto a glass surface using a compressor. There are standards on the size of emery grains (grain size). The grain size is normally indicated by a number with a hash sign (#) in front of it. Lower numbers are for coarse grain and higher numbers for fine grain.
In printing, emery is used to polish the stone plate. When using a stone plate to carry out lithography, the surface of the plate must first be polished. This is done by sprinkling emery powder on the surface, placing either another stone plate or a metal board over the top, and rubbing the two surfaces together with an adequate amount of water for lubrication. Begin with the coarse grain powder first and gradually replace with finer powder. The finish will determine the tone of the stone plate. A polished plate will have a smooth and flat surface with no visible grain. This is suitable for making copies and for drawing in pen. Conversely, the plate can also be turned into a grained plate, which has a rougher surface, by grinding the surface with a grinding stone and then spreading emery powder and polishing it with no or very little water. If emery with a high grain size number is used to produce fine grain on the surface, the plate will be suitable for drawing detailed images in crayon. If emery with a low grain size number is used to produce a rough surface, the plate will be suitable for printing with a thick coat of ink. In recent years, it is becoming increasingly more popular to use a synthetic abrasive known as carborundum (silicon carbide) instead of emery. Carborundum is black and is harder and sharper than emery. Emery can be purchased at printing supply stores and shops selling industrial supplies.
- Emery #80