55 - A Beautiful and Whiter Lattimo.
I took 400 pounds of crystal frit, 60 of tin calx, and 2-½ pounds of prepared Piedmont manganese. I pulverized everything and mixed it thoroughly with the frit. I put it into a crucible, and left it to heat and clarify in the furnace. At the end of 18 days it was fully clarified. I emptied this material into water, and then returned it to the crucible.
As a test, I took some clarified glass, and because it was still a little clear, 15 pounds more of the above calx was added. Tin calx is very common to have at the furnace. I then stirred the glass thoroughly, and at the end of a day, it became most beautiful and marvellous. In whiteness, it exceeded any snowfall, and was ready to work. I have made it many times in this manner, and it always proved to be good. Rocchetta can also make lattimo, but it does not come out as nice and white as with crystal. So if you want [your work] to be exquisite, you must always make it with crystal.