Dictionarium polygraphicum. To make German BLUE.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol I.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
1735
Take sal armoniack two pounds, flowers of sulphur three quarters of a pound, quick lime half a pound; pound and grind them in an iron or marble mortar, till the mercury is wholly mortified and disappears; then put it into a glass body, well luted up to the middle; set it in a very gentle lime; sand heat uncovered, till all the moisture is vanished. Stop it close, and increase heat gradually, to make the mass sublime; so will you have an excellent azure or Blue, which grind on a porphyry to a subtil powder for use in painting.