70 - Sapphire Color in Lead Glass.
Take 15 pounds of crystal frit and 12 pounds of Iead calx. Mix these very well and pass them through a sieve. Once sifted, add 2 ounces of prepared zaffer and a pennyweight of Piedmont manganese, also prepared. Now, mix all this material well, put it into a crucible and leave it for 12 hours.
Then empty the glass into water. Separate any metallic Iead that has precipitated out in the glass, as well as in the pot. Do this with exquisite diligence. Then return the glass to the crucible and leave it to clarify for 12 hours.
At that point, check it to see if the colour needs adjustment to be satisfactory for the jobs that it must serve. To that end, you can load it with more or less color. ln order to come out well you must work it duly with the observations and diligences that are necessary for Iead glass. You will then have a glass that resembles oriental sapphire; most attractive, with a hint of double violet colour, which makes it quite nice in appearance.