2375. To Etch or Write on Glass

2375.    To Etch or Write on Glass. A writer in Dingler's "Polytechnisches Journal" recommends a solution of fluoride of ammonium, which can be used with an ordinary quill, and on drying leaves a distinct line.

2376. To Engrave on Glass

2376.    To Engrave on Glass. To engrave on glass, fluoric acid is used, either in the liquid state or in vapor. This acid is kept in metal bottles, and requires very careful handling. The glass must be warmed, and coated with wax, or engravers' cement, and the writing or design traced through the wax with a pointed instrument. The liquid fluoric acid is poured on it, and left to act on the uncovered portions of the glass; or pour some of the acid in a small lead pan, which place in a still larger vessel filled with sand; heat the sand and place the glass object over the gas liberated from the heated acid, and it will soon be found to be beautifully etched. Great care must be taken when this is going on, for the gas, as well as the acid, is of a very deleterious character. The same effect may be produced by the use of fluorspar, powdered and made into a paste with oil of vitriol, laid over the prepared surface, and covered with lead-foil or tea-lead; or bruised fluorspar is put in a wedgwood evaporating basin, with sufficient oil of vitriol to form a thin paste, and the prepared glass laid over the basin, so that the vapors may act on the portions from which the wax has been removed.

2377. Glass of Borax

2377.    Glass of Borax. Calcine borax with a strong heat till the water of crystallization is expelled, and the salt fuses into a clear glass.