93 - The Material to Make All Enamels
Take for example 30 lbs of fine lead, and 33 lbs of fine tin. Blend these metals together and calcine them in the kiln, as was described for Iead in its place [chapter 62], and then pass this calx through a sieve. Boil the calx in clear water, in a clean earthenware vessel, which is to say in a kettle. When it has boiled a little, lift it from the fire and empty the water per your inclination, so that it will carry away the finer metallic calx. Replace it with new water over the sediment of the calx, and return it to boil. Decant this as above, and repeat many times. Do this so the water does not carry with it the bulk of the calx, so that the larger sediment will remain in the bottom.
In order to get finer pastes, retum the calx to calcine and then boil it in common water, as above. Then evaporate all the water that has carried with it the fine part of the calx. Do this on a low fire, especially near the end so as not to spoil the calx. The finest calx will remain in the bottom, much more so than usual.
Take 50 lbs of this fine calx, and 50 lbs of crystal frit made with thoroughly ground white tarso. Through a sieve, sift 8 oz of white tartar salt, as previously instructed. Thoroughly pulverize everything, and mix it together, pass it through a sieve, and set this material down in the terracotta pot again, giving it fire for 10 hours. Remove the material, pulverize it well, and store it in a dry place. Cover it so dust does not get inside, since this is the [base] material to make all enamels, in all the colours.