Dictionarium polygraphicum. Bollito.

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
BOLLITO a name by which the Italians call a sea green colour in artificial crystal.

This colour is not to be made without a great deal of precaution.

To succeed well, you must have in the furnace a pot fill’d with forty pound of good crystal frit, carefully skimm’d, boil'd and purified, without any manganeze.

Then you must have twelve ounces of the powder of small leaves of copper thrice calcin'd, as directed in the article COPPER. And half an ounce of zaffer in powder, prepar'd as directed in the article ZAFFER.

Mix these powders together, and put them at four times into the pot, that they may the better mix with the glass, stirring them well each time of putting in the powder, for fear it should swell too much and run over.

After the whole has been incorporated, well mix'd and pretty well settled for two hours, try if the colour is deep enough, if so, let it rest, though the sea green or sky colour seems at first greenish, you need not be concern’d at it; for the salt in the glass will consume all that greenness, and change it into blue.

After the metal has stood at rest for twenty four hours, it may be wrought, and you'll have the colour deeper or lighter, according to the quantity of powder you have put into it.

There is no other rule for that but the fancy of the work man, for which reason it cannot be ascertained; besides, the matter that is us’d for tinging glass, makes it have some more colour, some less, which proceeds from the preparation of it.