Pound it in a covered bronze mortar, that the powder may not fly away; then put it on your slab porphyry, and grind it without water; afterwards, take a covered strainer like that used by the druggists for sifting drugs (spices), and sift it and pound again as much as is required. But bear in mind that though the more you grind, the more finely powdered the azzurro will be, yet it will not be so beautiful and rich and deep in colour; and that the finely ground sort is fit for miniature-painters, and for draperies inclining to white.

When the powder is prepared, procure from the druggist, six ounces of resin of the pine, three ounces of mastic, and three ounces of new wax to each pound of lapis lazuli. Put all these ingredients into a new pipkin and melt them together. Then take a piece of white linen and strain these things into a glazed basin.

Then take a pound of the powder of lapis lazuli; mix it all well together into a paste, and that you may be able to handle the paste, take linseed oil, and keep your hands always well anointed with this oil. This paste must be kept at least three days and three nights, kneading it a little every day; and remember that you may keep it for fifteen days or a month, or as long as you please.

When you would extract the azure from the paste, proceed thus. Make two sticks of strong wood, neither too thick nor too thin, about a foot long; let them be well rounded at each end and well polished (smoothed). Then, your paste being in the glazed basin into which you first put it, add to it a porringerful of lye, moderately warm; and with these two sticks, one In each hand, turn and squeeze and knead the paste thoroughly, exactly in the manner that you would knead bread.

When you see that the lye is thoroughly blue, pour it put into a glazed basin; take the same quantity of fresh lye, pour it over the paste, and work it with the sticks as before. When this lye is very blue, pour it into another glazed basin, and continue to do so for several days, until the paste no longer tinges the lye.

Then throw it away, it is good for nothing. Range all the basins before you on a table in order, that is to say, the first, second, third, and fourth ; then beginning at the first, with your hand stir up the lye with the azure, which by its weight will have sunk to the bottom, and then you will know the depth of colour of the azure. Consider how many shades of the azure you will have, whether three, or four, or six, or what number you please, always remembering that the first- drawn extracts are the best, as the first basin is better than the second.”