Dictionarium polygraphicum. Gums.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol I.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
1735
The chief of all is Gum Arabic, that which is white, clear and brittle; the Gum water of it is made thus.
Take Gum Arabick, bruise it, and tye it up in a fine clean linen cloth; then put it in a convenient quantity of pure spring water in a glass or earthen vessel, letting the Gum remain there till it is dissolv’d; which being done, if the water be not stiff enough, put more Gum into the cloth; but if too stiff, add more Water.
Of which Gum water have two sorts by you, the one strong and the other weak; of which you may make a third at pleasure.

But if Gum Arabick is not to be had, use the following preparation of sheep's leather or parchment.
Take the shreds of white sheep skins, (which are to be had at the glovers) or else cuttings of parchment one pound, of con duit or running water two quarts; boil it to a thin gelly, then strain it whilst hot through a fine strainer, and so use it.

Gum lake is made with whites of eggs, beaten and strain'd a pint, honey, Gum Hedera, of each two drams, strong wort four spoonfuls, mix them and strain them with a piece of sponge, till they runlike a clear oil, which keep in a clean vessel, till it grows hard.
This Gum will dissolve in water like Gum Arabick, it is a good ordinary varnish for pictures.

Gum Hedera, Gum of Ivy is gotten out of Ivy, by cutting with an ax a great branch thereof climbing upon an oaken tree, and bruising the ends of it with the head of the ax; at a month's end or thereabouts, you may take from it a very clear, and pure fine Gum, like oil.
This is good to put into gold size, and other colours for these three reasons.
1. It abates the ill scent of the size.
2. it will prevent bubbles in gold size, and other colours.
3. Lastly, it takes away the sat and clamminess of colours.

Gum Ammoniacum is a foreign Gum, and ought to be bought strain'd. Grind it very fine with juice of garlick, and a little Gum Arabick water, so that it may not be too thick; but that you may write with it what you will.
When you use it, draw what you will with it, and let it dry, and when you gild upon it, cut your gold or silver to the fashion you have drawn with the size or gum; then breathe upon the size, and lay the gold upon it, gently taken up, which press down hard with a piece of wool, and then let it be well dry’d; when it is dry'd, strike off the loose gold with a fine cloth; and so what was drawn will be fairly gilded, if it were as fine as a hair. It is call'd gold ammoniack.