RING, HOW TO SOLDER A JEWELED: See Solders.
RINGS ON METAL, PRODUCING COLORED: See Plating.
ROACH EXTERMINATORS: See Insecticides.
ROBURITE: See Explosives.
RODINAL DEVELOPER: See Photography.
ROLLER COMPOSITIONS FOR PRINTERS.
Rollers for transferring ink to types have to possess special properties, which have reference both to the nature of the ink and that of the types to which it is to be transferred. They must be as little liable as possible to changes of temperature. They must be sticky, but only just sticky enough, and must have elasticity enough to exert a uniform pressure over the varying surface with which they meet in the form. Originally, the composition was one of glue and molasses in varying proportions, and the only practical improvement that has been made is the addition of glycerine. This being slightly hygroscopic, helps to keep the roller at the right degree of softness, and being practically unfreezable, it is a great assistance in keeping the rollers from hardening in cold weather.
The recipes given in technical works for printing roller compositions are numerous and very different. All contain glue and molasses, and it is the practice to put a larger proportion of glue in rollers to be used in the summer than in those intended for winter use. The following is a selection of recipes:
I.—Soak 8 pounds of glue in as much water as it will absorb. When there is no visible water, treat the glue till melted, and add 7 pounds of hot molasses.
| II.— | Glue (summer) | 8 pounds |
|---|---|---|
| Glue (winter) | 4 pounds | |
| Molasses | 1 gallon | |
| III.— | Molasses | 12 pounds |
| Glue | 4 pounds | |
| IV.— | Molasses | 24 pounds |
| Glue | 16 pounds | |
| Paris white | 2 pounds | |
| V.— | Glue or gelatin | 64 pounds |
| Water | 48 pounds | |
| Linseed oil | 96 pounds | |
| Molasses or sugar | 64 to 96 pounds | |
| Chloride of calcium | 3 pounds | |
| Powdered rosin | 8 pounds |