or FRITT, in the glass manufacture, is the matter or ingredients whereof glass is to be made, when they have been calcined or baked in a furnace.

A salt drawn from the ashes of the plant kali, or from fern or other plants, mixed with sand or flint, and baked together, makes an opaque mass called by glasmen frit; probably from the Italian frittare, to fry; or because the frit, when melted, runs into lumps, like fritters, called by the Italians fritelli.

Frit, by the ancients, was called ammonitrum, of aquae, sand, and vitrum, nitre; under which name it is described by Pliny thus: Fine sand from the Volturnian sea, mixed with three times the quantity of nitre, and melted, makes a mass called ammonitrum; which being rebaked makes pure glass.

Frit, Neri observes, is only the calx of the materials which make glass; which, though they might be melted, and glass be made, without thus calcining them, yet it would take up much more time. This calcining, or making of frit, serves to mix and incorporate the ma- terials together, and to evaporate all the superfluous humidity. The frit, once made, is readily fused, and turned into glass.

There are three kinds of frits. The first, crystal frit, or that for crystal metal, is made with salt of pulverine and sand. The second, and ordinary frit, is made of the bare ashes of pulverine or barilla, without extracting the salt from them. This makes the ordinary white or crystal metal. The third is frit for green glaisses, made of common ashes, without any preparation. This last frit will require ten or twelve hours baking.

The materials in each are to be finely powdered, washed, and leached; then equally mixed, and frequently stirred together in the melting pot. See Glass.