6. From Tin.—The oxide of tin, which is of a white co lour, renders opaque the glass with which it is melted, and -forms white enamel. For this purpose, calcine the putty of tin ; then wash and dry it, and sift it through a silk sieve. Take six pounds of the second base, (See GEms) the same quantity of the calcined putty of tin, and 43 grains of man ganese.
7. From ?intimony.—Antimony is only susceptible of vi trification in a certain state of oxidation, and then it pro duces a reddish hyacinth-coloured glass ; but if the anti mony be in a state of absolute calx, such as the diaphoretic antimony, then it is no longer vitrifiable, and may be sub, stituted for oxide of tin, to make white enamel.
8. From Manganesc.—Employed in a small quantity, this metallic substance renders the glass whiter ; a larger quantity produces a very fine violet colour, and a still larger dose minters the glass black and opaque. Thcrc are two of prepaying manganese. The inoA. simple consists in exposing it to a red heat, and then quenching it with dis tilled vinegar : it is then dried and powdet et', in order to pass it through a silk sieve. The other method of pre paring the manganese proper to furnish a red colour, is de scribed by Blancourt, who call it " fusible manganese." Take of manganese of Piedmont, one pound ; torrefy and pulverize it ; then mix it with a pound of nitre, and calcine the mixture during 24 hours ; afterwards wash it repeated ly in warm water, till the water of the legs has no longer any taste ; dry the manganese, and mix with it an equal weight of sal ammoniac ; levigate this mixture on a slab of porphyry, with sulphuric acid, diluted with water to the strength of vinegar. Dry the mixture, and introduce it in to a cornme: distil by a graduated-fire ; and when the sal ammoniac is sublimed, weigh it, and add to the mixture an equal quantity. Then distil and sublime as before, and repeat the operation six times, being careful at each time to mix the sal ammoniac and the manganese upon the por phyry with diluted sulphuric acid.
Compositions.—To make the white diamond, take the Mayence base. This base is very pure, and has no colour. It is similar to the beautiful white paste, so generally known by the appellation of Strass.
For the Yellow Diamond.—To an ounce of the fourth base, add, for colour, 24 grains of horn silver, or ten grains of glass of antimony.
For the SaN2hire.—To 24 ounces of the Mayence base, add two drachms 46 grains of the calx of cobalt.
For the Oriental Ruby.-1. To 16 ounces of the May ence base, ado a mixture of 2 drachms 48 grains of the pre cipitate of Cassius, the same quantity of crocus martis pre pared in aquafortis, the same of golden sulphur of antimony and of fusible manganese, with the addition of two ounces of rock crystal : or, 2. To 20 ounces of the base made with flints, add half an ounce of fusible manganese, and two ounces of rock crystal.
For the Batas Ruby.-1. To 16 ounces of the Mayence base, acid the above colouring powder, but diminished a fourth part : or, 2. To 20 ounces of the base made with flints, add the same colouring powder, but with a fourth less of the manganese.
For the Brazil Topaz.—To 24 ounces of the second or third base, add, for colour, 1 ounce 24 grains of the glass of antimony, and 8 grains of the precipitate of Cassius.
For the Saxon Topaz—To 24 ounces of the first or third base, add six drachms of the glass of antimony.
For the Emerald.-1. To 15 ounces of either of the bases, add, for colour, one drachm of mountain blue and six grains of glass of antimony ; or, 2. To an ounce of the second base, add, for colour, 20 grains of glass of antimony, and three grains of calx of cobalt.
For the Common Opal.—To an ounce of the third base, add, for colour, 10 grains of horn-silver, two grains of cal cined magnet, and 26 grains of an absorbent earth.
Glass staining is the method of ornamenting glass *for the windows of churches, or other edifices, by pictures or de signs painted in colours, which are made to penetrate into the substance of the glass, by means of fire. Stained glass is frequently called painted glass, but the distinction should always be preserved between the painting with transparent colours upon a surface of glass, and the staining or tinging of the glass itself, with the colours which produce the pic ture. As pictures in coloured glass are always placed be tween the spectator and the light, they have an elfect alto gether different from any other species of painting ; and, from the transparent brilliancy of the colouring, the spec tator is often struck with admiration, independent of any excellence in the subject of the picture.