A Colorless Cement for Joining Sheets of Mica.
A colorless cement for joining sheets of mica is prepared as follows:—Clear gelatine softened by soaking it in a little cold water, and the excess of water pressed out by gently squeezing it in a cloth. It is then heated over a water bath until it begins to melt, and just enough hot proof spirit (not in excess) stirred in to make it fluid. To each pint of this solution is gradually added, while stirring, one-fourth ounce of sal-ammoniac and one and one-third ounces of gum mastic, previously dissolved in four ounces of rectified spirits. It must be warmed to liquefy it for use, and kept in stoppered bottles when not required. This cement, when properly prepared, resists cold water.