Verdigris is prepared in two ways.

The preparation of medicinal verdigris.

There are also various ways to make verdigris from copper, which need not all be listed here. We shall describe only two, with different preparations: one for medicine and the other for alchemy. Verdigris intended for medicinal use has this process. Take copper plates and anoint them with the following material: equal portions of honey and vinegar and enough salt to make a rather thick paste from the three, mixing well. Place them in a reverberatory or pottery kiln until the potter has fired the vessels. You will see the material adhering to the plates is black, but do not let this concern or frighten you. If you hang or place those plates in air, the whole black material becomes green in a few days, producing very fine verdigris which may be called the balsam of copper and is highly praised by all physicians. Nor should you wonder that this verdigris becomes green only in air, and that air can change black into so beautiful a green. Every dead earth or caput mortuum, as soon as it comes from fire into air, very quickly acquires another colour and abandons the colour it assumed in fire, as daily alchemical experience demonstrates. These colour changes vary according to the material, though they mostly flow from the blackness of dead earth. Those skilled in alchemy see that every dead earth of fixed powder or aqua fortis comes black from fire. The more ingredients there are, the more variously colours appear in air: sometimes only red, as with vitriol; sometimes only yellow, white, green or blue; sometimes mixed, as in a rainbow or peacock’s tail. All these colours appear after death and from death. In the death of all natural things other colours are seen, and each changes from its first colour to another according to its nature and property.

The balsam of copper.

Air changes the colours of burnt things.

The preparation of alchemical verdigris.

Let us now speak of the verdigris assigned to alchemy. Its preparation and process are as follows. Beat copper into extremely thin plates and layer it in a large crucible with equal portions of salt, sulphur and tartar, ground and mixed. Reverberate in a strong fire for twenty-four hours, yet do not allow the copper plates to melt. Remove it, break the crucible and expose the plates with the adhering material to air for a few days. The material on the plates will become very fine verdigris, which in all aquae fortes, waters of gradation, cements and colourings of gold tinges gold and silver with a deep colour.

How burnt copper or crocus of Copper is prepared.

To make burnt copper, also called crocus of copper, proceed in this way. Beat copper into plates and anoint them with salt made into a paste with the best vinegar. Place them in a large crucible in a wind furnace and burn them in a strong fire for a quarter of an hour, without allowing the plates to melt. Quench the glowing plates in vinegar containing dissolved sal ammoniac, always half an ounce to a pound of vinegar. Heat them again and quench as before. Always scrape the scales adhering to the plates after quenching into the vinegar, or knock them off, or remove them however you can. Continue until a good part of the copper plates has been consumed. Then draw off the vinegar by distillation, or let it evaporate in an open vessel, and coagulate it into a very hard stone. You thus have the highest crocus of copper for use in alchemy. Many ordinarily make burnt copper or crocus of Venus from Copper by extraction with alcohol of wine—others with vinegar—as they do crocus of Mars. I praise this method much more.

How sublimed Mercury is made.

Mercury is mortified for sublimation through vitriol and salt: mix it with these two and sublime it from them. It thus becomes hard like crystal and white like snow. To reduce Mercury to a precipitate, proceed by calcining it in the best aqua fortis, then draw graduated aqua fortis off from it about five times, more or less, until the precipitate acquires a fine red colour. Sweeten this precipitate as much as possible. Finally distil rectified ardent wine from it seven or nine times, or until it glows in fire without fleeing. You then have diaphoretic precipitated Mercury.

How fixed diaphoretic precipitate is made.