Pressed glass was many times reheated to a point sufficient to melt a thin surface layer—This was called “fire polishing.” It removed any roughness due to the process of molding and left a smooth bright surface.

Flint glass—The name of flint glass was derived from the fact that in England flints were calcined and pulverized to make silica which is the main constituent of glass. The use of flint made the glass highly refractive and brilliant and oxide of lead which was also added increased it.

As pressed glass was the main product of the Sandwich works the few blown specimens of the factory will be taken up by the author in a separate volume dealing with the blown pitchers, plates, flips, jars, and balls blown at Willington, Westford, New London, Stoddard, Lyndeboro, Keene, and Chelmsford.