Glazes. Glazes must be reduced to a very fine powder. For use they are ground with water to a very thin paste or smooth cream, into which the articles, previously baked to the state called "biscuit," are then dropped; they are afterwards exposed to a sufficient heat in the kiln to fuse the glaze. Another method of applying them is to immerse the biscuit in water for a minute or so, and then to sprinkle the dry powder over the moistened surface.

2405. White Glazing

2405.    White Glazing. Prepare an intimate mixture of 4 parts massicot (see Index),

2 parts tin ashes, 3 of crystal glass fragments, and 1/2 part sea salt. The mixture is suffered to melt in earthenware vessels, when the liquid flux may be made use of.

2406. Yellow Glazing

2406.     Yellow Glazing. Take equal parts of massicot, red lead, and sulphuret of antimony. Calcine the mixture and reduce it again to powder, add then 2 parts of pure sand and l1/2 parts of salt. Melt the whole.

2407. Green Glazing

2407.    Green Glazing. Sand, 2 parts;

3   parts massicot, 1 part of salt and copper scales, according to the shade to be produced. The mixture is melted as directed above.

2408. Violet Glazing

2408.   Violet Glazing. Massicot, 1 part; 3 parts sand, 1 of smalt, and 1/8 part black oxide of manganese.

2409. Blue Glazing

2409.    Blue Glazing. White sand and massicot, equal parts, 1/3 part of blue smalt.

2410. Black Glazing

2410.    Black Glazing. Black oxide of manganese, 2 parts; 1 of smalt, 11/2 of burned quartz, and 11/2 massicot.

2411. Brown Glazing

2411.    Brown Glazing. Take 1 part broken green bottle glass, 1 of manganese, and 2 parts lead glass.

2412. Glaze without Lead

2412.    Glaze without Lead. Common earthenware is glazed with a composition containing lead, on which account it is unfit for many purposes. The following glaze has been proposed, among others, as a substitute: 100 parts washed sand, 80 parts purified potash, 10 of nitre, and 20 of slacked lime, all well mixed, and heated in a black-lead crucible, in a reverberatory furnace, till the mass flows into a clear glass. It is then to be reduced to powder. The goods to be slightly burnt, dipped in water, and sprinkled with the powder.

2413. Glaze for Porcelain

2413.    Glaze for Porcelain. Feldspar, 27 parts; borax, 18 parts; Lynn sand, 4 parts; nitre, 3 parts; soda, 3 parts; Cornwall china-clay, 3 parts. Melt together to form a frit, and reduce it to a powder with 3 parts calcined borax.

2414. Metallic Lustres for Pottery

2414.    Metallic Lustres for Pottery. The appearance of a lustrous metallic surface is given to vessels of stoneware, etc., by applying the lustre over an easily-fusible glaze to the outer surface of the vessel, after which adhesure is produced by exposing it to a slight degree of heat. They are then polished with cotton or leather. The principal lustres are given in the following receipts:

2415. Gold Lustre

2415.    Gold Lustre. Dissolve 1 drachm grain-gold in 3/4 ounce aqua-regia, add 6 grains metallic tin to the solution. When dissolved, pour it gradually, with constant stirring, into a mixture of 1/2 drachm balsam of sulphur, (see Index), and 20 grains oil of turpentine. When the mass begins to stiffen, an additional 1/2 drachm oil of turpentine must be added and well mixed in. More gold deepens and brightens the lustre; more tin turns it on the violet or purple. Applied as in No. 2414.

2416. Iron Lustre

2416.    Iron Lustre. This is a mixture of muriate of iron and spirit of tar. Used according to No. 2414.

2417. Platinum Lustre

2417.    Platinum Lustre. To bichloride of platinum (a solution of platina in aqua-regia), is added drop by drop a mixture of spirit of tar and balsam of sulphur in equal proportions, until by a trial the composition is found to give the required result. This gives the appearance of polished steel. (See No. 2414 (Metallic Lustres for Pottery).)

2418. Silver Lustre

2418. Silver Lustre. Reduce ammonio-chloride of platinum to an impalpable powder; grind it to the requisite consistence with a little spirit of tar, and apply with a brush as directed in No. 2414.