Dictionarium polygraphicum. To make a milk white colour in glass. Another fairer and whiter colour. To make common glass become white and crystalline. To make marble colour in glass.

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 a MILK WHITE colour in GLASS.
To make the milk white colour well, requires no less exactness than the blue.
To succeed in it, take twelve pounds of good crystal frit, two pounds of calx of lead and tin, one of each, and half an ounce of manganese of Piedmont prepar’d; the whole being pulveriz'd and mixt together, put them into a pot heated in the furnace; let it stand there for twelve hours, then mix the whole well and make an essay of it.
If the colour don't please you, add to it some calx of the two metals beforementioned, which incorporate with the glass, mixing it well. In eight hours time after the glass will be fit to work, and white as milk.


Another fairer and whiter colour.
This second way of giving a milk white colour to glass is much better than the precedent, and the work more exquisite.
We only make use of calx of tin, without mixing any lead, and we put fifteen pounds of that calx to a hundred pounds of pure crystal frit, with twelve ounces of manganese of Piedmont prepar'd; the whole being well pulveriz'd and mix’d, put it into a pot heated in the furnace, there to purify during eight days.
Then cast the matter into water, the better to purify it; then after it has been dry'd, put it into the same pot to be melted again.
If it be transparent, you must add three pounds twelve ounces of the same calx of tin as before, mixing it well with the melted metal, to make it the better incorporate; and in twenty four hours it will be finer and whiter than snow, and fit to be wrought.


To make common GLASS become white and CRYSTAL LINE.
If you put in a convenient pot frit of polverine, you will have a common white glass.
If you add salt of rochetta to this fritt, you will have a very fair crystal glass, which will be between ordinary glass and crystal.
To make it very fine, you must add the same dose of manganese of Piedmont prepar'd as for crystal; for the manganese takes away all greenness in the glass, and makes it very white.
If you would have a very fine glass, you must always cast the crystalline matter into water; you may also do the same by common glass to bring it to perfection.
When this has been done, put the matter into the pot again, and when it is melted, put it again into water, repeating this till it be purified and made fine.
To have glass finer than ordinary, this casting of it into water must be very exactly observ’d; for besides its whitening, it is there calcin’d and purified, and has fewer blisters and pustles.
But to raise the matter to the greatest perfection, mix fifty pounds of crystalline glass, and as much common, and put to it ten pounds of purified salt of tartar; that will give a glass and crystal more than ordinary fine, provided you always take care not to mix it with the collets of the glass, which has touch'd the iron rod; for they always make the glass blackish, and are only fit for green glass.


To make marble colour in GLASS.
White marble being very simple, it is easy to imitate; the way of doing it only requires crystal frit, which must be wrought as soon as it is melted, before it be purified, for so it will give a very fair marble colour.