Dictionarium polygraphicum. Copper Green.

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
To make this, take a pound of right French verdegrease made at Montpelier, that being the best, because the verdegrease made at any other place will fade.

To this add three ounces of cream of tartar; let them be both reduc’d to a very fine powder; but be sure to take care to stop your nose while the verdegrease is pounding, and hold a bunch of fine linen in your mouth, to breathe through; or otherwise the subtil powder of the verdegrease will offend you.

When this is done, mix both the powders in two quarts of water, and boil them in an earthen pipkin to the consumption of one half; then set it by till it is cold; then strain it, and put the liquor into a glass bottle; stop it up, and let it stand to settle till the liquor be very clear, and so you will have a delicate green water for washing prints, &c.

But the verdegrease not being always of a goodness, some times the colour may not prove so deep as you would have it for some uses.

To remedy this, put some of it into a broad earthen dish, and set it over a chafing dish of coals, and by a gentle heat, cause so much of the liquid part to evaporate, till by trying on a paper, and letting of it dry, the colour is as you would have 1t. Here you may note, that if it shine too much when dry, it is not as it ought to be, for it is not rightly made, if it does any more than just shine; and if you cannot make the colour by evaporating it (as before) without making it shine too much, the best way will be to add some more verdegrease, and boil it up again, till it becomes a transparent deep willow green.