Silver Solder of Silver and Red Copper With a Burnt Wine-Stone Flux (Theophilus, 12th Century)

"Weigh two parts of pure silver, and a third (part) of red copper, and mix and finely rasp into a clean vessel."

Weigh two parts of pure silver and a third part of red copper, melt them together, and rasp the alloy finely into a clean vessel; keep the filings in a quill.

Take wine-stone from a vessel in which good wine has stood a long time, tie pieces in a cloth and put it in the fire until no more vapour comes from it. When cool, blow off the cloth ash and grind the burnt stone in a copper vessel with a round mallet, mixing in water and salt until it is as thick as lees.

With a thin piece of wood paint the flux round the joint inside and out, shake the filed solder over it with a small iron, and dry it. Paint more flux on, more thickly than before, put the work in the fire, cover it with coals and blow gently with a long breath until the solder has melted. Take it out, let it cool slightly and wash it. If the joint is not firm, do it again. Then file and scrape it smooth.

From Theophilus, **De Diversis Artibus**, Book III, chapter XXXI, translated by Robert Hendrie (1847) (checked on the archive.org scan essayuponvarious00hend, pp. 241-243). "A third (part)" can be read two ways; both are shown. Melting the alloy before rasping, the tools and the diagram are ours.