VARNISH, a thick, viscous, shining liquor, used by painters, gilders, and various other artificers, to give a gloss and lustre to the works; as also to defend them from the weather, dust, &c.
There are several kinds of varnishes in use; as the siccative or drying varnish, made of oil of aspin, turpentine, and sandarach melted together. White varnish, called also Venetian varnish, made of oil of turpentine, fine turpentine, and mastic. Spirit of wine varnish, made of sandarach, white amber, gum elemi, and mastic; serving to gild leather, picture-frames, &c. withal.
1. To make the white varnish: take gum sandarach, of the clearest and whitest sort, eight ounces; gum mastic, of the clearest sort, half an ounce; of sarcocolla, the whitest, three quarters of an ounce; Venice turpentine, an ounce and a half; benzoin, the clearest, one quarter of an ounce: white rosin, one quarter of an ounce; gum animæ, three quarters of an ounce: let all these be dissolved, and mixed in the manner following:
Put the sarcocolla and rosin into a little more spirits than will cover them to dissolve; then add the benzoin, gum animæ, and Venice-turpentine, into either a glass or glazed earthen vessel, and pour on as much spirits as will cover them an inch; then put the gum mastic into a glass or glazed vessel, and pour strong spirits upon it, covering it also about an inch thick, to dissolve it rightly; then put your gum elemi into a distinct vessel as before, and cover it with spirits to dissolve.
For this purpose, you need only break the rosin a little, and powder the gum animæ, sarcocolla, and benzoin.
Let all stand three or four days to dissolve, shaking the glasses, &c. two or three times a-day, and afterwards put them all together into a glazed vessel, stirring them well, and strain the liquor and gums gently, beginning with the gums, through a linen cloth.
Then put it into a bottle, and let it stand a week before you use it, and pour off as much of the clear only, as you think sufficient for present use.
A hard varnish that will bear the muffle may be thus made: Take of colophony, an ounce; set it over the fire in a well-glazed earthen vessel, till it is melted; then by little and little, strew in two ounces of powder of amber, keeping it stirring all the while with a stick; and when you perceive it begin to harden or resist the stick, then put in a little turpentine oil, which will thin and soften it immediately; then put in two ounces of gum copal, finely powdered, sprinkling it in as you did the amber, now and then pouring in a little oil of turpentine; and when it is done, strain it as before directed.
This is proper to varnish over gold; and the things done with it must be set into a declining oven, three or
four days successively, and then it will resist even the fire itself.
To make a varnish for gold, or metals made in imitation of gold. Take colophony, and, having melted it, put in two ounces of amber finely powdered, and some spirit of turpentine; and, as the amber thickens, keep it well stirring: then put in an ounce of gum elemi, well pulverized, and more spirit of turpentine; constantly stirring the liquor till all is well mixed and incorporated: but take care, however, to use as little turpentine as you can, because the thicker the varnish is made, the harder it will be. Let this be done over a sand-heat, in an open-glass: then strain it, as is directed for the preceding varnish. This varnish is to be used alone, first warming the vessels made of paper paste; and lay it on with a painting-brush before the fire, but not too near, lest the fire raise it into blisters. After this has been done, harden it three several times in ovens; first with a slack heat, the next with a warmer, and the third with a very hot one; and the vessels will look like polished gold.
And as for such vessels, &c. as shall be made with sawdust and gums, the varnish may be made of the same ingredients as above-mentioned, except the gum elemi; and this will dry in the sun, or in a gentle warmth.
To make a varnish for any thing covered with leaf-silver. First paint the thing over with size, and ground chalk or whitening; let them stand till they are thoroughly dry, and then do them over with very good gold-size of a bright colour (for there is much difference in the colour of it, some being yellow, and others almost white; the first is most proper for gold, and the last for silver. When this size is so dry as that it will just stick a little to the touch, lay on the leaf-silver, and close it well to the size.
To make a varnish for silver. Melt, in a well-glazed pipkin, some fine turpentine, and put in three ounces of white amber finely powdered (more or less, according to the quantity your work will require;) put it in by little and little, keeping it continually stirring, adding by degrees some spirit of turpentine, till all the amber is dissolved; and then add to it an ounce of sarcocolla well beaten, and an ounce of gum elemi well levigated, adding now and then a little spirit of turpentine, till all is dissolved: do this over a gentle fire, and keep it constantly stirring.
This varnish will be as white and strong as the former; and is to be used warm, and hardened by degrees in an oven, as varnished gold, whereby it will look like polished silver.