86 - An Oriental Sapphire Loaded with Colour
Take 2 oz of rock crystal ground impalpably, as was described in its place [chapter 76]. Add 5 oz of ordinary minium, which is 7 oz in all. To each ounce of this material, give a proportion of 6 grains of prepared zaffer, which will be 1 pwt and 18 grains [of zaffer] in all. lnto this zaffer, blend 8 grains of prepared Piedmont manganese. Unite these things together thoroughly, as was done with the other pastes. Put them in a crucible as usual, and cook them in a pottery furnace, or purpose-built kiln. They will make a deeper oriental sapphire of notable grace that has a tinge of violet.