SIZE is also a sort of paint, varnish, or glue, used by painters, &c.
The shreds and parings of leather, parchment, or vellum, being boiled in water and strained, make siz. This substance is used in many trades.
The manner of using siz is to melt some of it over a gentle fire; and scraping as much whiting into it as may only colour it, let them be well incorporated together; after which you may whiten frames, &c. with it. After it dries, melt the siz again, and put more whiting, and whiten the frames, &c. seven or eight times, letting it dry between each time: but before it is quite dry, between each washing, you must smooth and wet it over with a clean brush-pencil in fair water.
To make gold-siz, take gum animi and asphaltum, of each one ounce; minium, litharge of gold, and umber, of each half an ounce; reduce all into a very fine powder, and add to them four ounces of linseed-oil, and eight ounces of drying-oil; digest them over a gentle fire that does not flame, so that the mixture may only simmer, but not boil; for fear it should run over and set the house a-fire, keep it constantly stirring with a stick till all the ingredients are dissolved and incorporated, and do not leave off stirring it till it becomes thick and ropy; and being boiled enough, let it stand till it is almost cold, and then strain it through a coarse linen-cloth and keep it for use.
To prepare it for working, put what quantity you may have occasion to use in a horse-muscle shell, adding so much oil of turpentine as will dissolve it; and making it as thin as the bottom of your feed-lac varnish, hold it over a candle, and then strain it through a linen rag into another shell; add to these so much vermillion as will make
make it of a darkish-red: if it is too thick for drawing, you may thin it with some oil of turpentine. The chief use of this size is for laying on metals.
The best gold-size for burnishing, is made as follows: take fine bole, what quantity you please; grind it finely on a marble; then scrape into it a little beef-suet; grind all well together; after which mix a small proportion of parchment size with a double proportion of water, and it is done.
To make silver-size: take tobacco-pipe clay, in fine powder; into which scrape some black-lead and a little Genoa-soap; and grind them all together with parchment-size, as already directed.