Dictionarium polygraphicum. Verdeter, verditer, verditure.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol II.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
1735
Verdeter, verditer, verditure is properly a native mineral substance, of a stony consistence, and of a blue colour, but spangled with little shining points like gems; it is found in the mountains of Hungary and Moravia, and is the same that is also call'd lapis Armenius.

The green us'd by the painters, and call'd verditer, should be made of this stone well-ground and cleansed by washing.

But this stone being very rare, the verditer commonly us'd is not a native, but a factitious substance; which some say is prepared by casting wine or water upon new copper, as it comes red-hot out of the furnace, and catching the steams that rise from it upon copper-plates: others again say, it is prepar'd by dissolving copper-plates in wine, much after the manner of verdegrease.

But the method of making it in England is as follows:

The refiners pour their copper-water into an hundred pound weight of whiting, stirring them well together every day for some hours, 'till the water grows pale; then they pour that off, and set it by for further use, and pour on more of the green water, repeating this 'till the verditer is made; which they then take out, and lay on large pieces of chalk in the fun to dry.

The water which is pour'd off from the verditer, (which remains at the bottom of the tub) is put into a copper, and boil'd 'cill it comes to the confidence of water-gruel; now consisting principally of salt-petre reduc'd, most of the spirit of vitriol being gone with the copper into the verditer: and a dish full of this being put into the other materials for aqua-fortis, is redistill'd, and makes what they call a double water, which is near twice as good as that made without it.