NUMBER II.
A Composition for Coating Cylinders or Globes.
The most approved composition for lining glass cylinders or globes, is made with four parts of Venice turpentine, one part of rosin, and one of bee’s-wax.—They must be boiled together for about two hours over a slow fire, and stirred very frequently; afterwards the composition is left to cool, when it is fit for use.
If a cylinder or globe is to be lined with this mixture, a sufficient quantity must be pulverised, and introduced into the glass; then by holding the glass near the fire, the composition is melted, and by a little skill may be spread over all its internal surface, to about the thickness of a wafer.—The glass, however, must be heated very gradually, otherwise, there is danger of its breaking in the operation.