COLOURING, DYES & CHEMISTRY

Colouring Agents

The following is a generic list of substances that can be added to glass, pottery, paint, etc. to produce the specified colours:

Black	Lamp-black
	Charcoal
Brown	Burnt iron ore
White	White lead	produced by placing lead plates in pots of vinegar
	Calcined bones
	Lime-wash
Red	Red ochre	iron ore and clay
	Red lead	roasted white lead (fades with time)
	Vermillion	produced by heating a mixture of quicksilver and brimstone
Blue	Azurite	Blue copper ore
	Smalt	produced by heating alkali, sand, and blue vitriol
	Ultramarine	produced by grinding lapis lazuli in wax and oil, then kneading it in alkali
	Copper blue	produced by placing copper in stale urine (fades with time)
Green	Malachite	green copper ore
	Verdigris	produced by packing copper plates with fermenting grape skins
	Salt-green	produced by mixing vinegar, copper and salt
Yellow	Yellow ochre	iron ore and clay
	Orpiment	a mineral
	Saffron	dried crocus stigmas
	Ground gold leaf

Ink is produced by adding lamp black to a watery gum to produce a permanent colour, or by mixing oak galls with green vitriol for black inks which eventually fade to brown. Varnish is made by heating resins in oil, and will always darken with age. Tempera, a substance added to the paints used for murals, can be made from a variety of different substances including gum, alumina, glue, chalk, honey, egg whites whipped in water, or (if suitably desperate) earwax.

Lacquer is common only in the orient, although it may be known elsewhere. It is made from shellac, a substance secreted by the lac insect, and is generally painted on layer by layer onto wickerwork or thin wood, sometimes pre-covered by a very thin layer of fine clay.

Dyeing

The following can be used as dyes:

Black	Gall extract & green vitriol	(fades with time)
Red	Madder	From plant roots
	Archil	lichens + lime + stale urine
	Crimson	from certain insects
Blue	Indigo
	Woad	fermented in water then stored in watertight barrels
Green	Verdigris	(see above)
Yellow	Weld	from the plant 'dyer's rocket'
Purple	Imperial purple	from certain molluscs (very expensive)

Alum is the essential ingredient of most permanent dyes. Deposits of high quality alum are rare, and material produced from them can demand high prices. The alum is purified before use by crystallising it out in a solution of stale urine.

An inferior but cheap alternative to alum is argol, a deposit found in wine casks.

MEDIEVAL CHEMISTRY

Caustic potash is made by percolating water through a mixture of wood ash and lime. Boiling it with tallow produces a foul smelling gooey substance called soap, which can be used in a variety of processes (although you would be well advised not to try washing with it!)

Stale urine is widely used for a variety of processes. Alkali is a concentrated form of stale urine, the very strongest form of which is known as ammonia. Ammonia can be used to clean up grease, and as an additive to alum.

A variety of pieces of equipment are used by alchemists. These include, but are by no means limited to stills, alembics, beakers, flasks, phials, basins, pots, candle lamps, braziers, smelting furnaces, wind furnaces, bellows, files, spatulas, hammers, ladles, shears, tongs, forceps, moulds, water-baths, crucibles and double-crucibles. One of the more sophisticated pieces of equipment is the curcubit, which consists of an earthenware jar with an ambix (a long brass tube) attached to the top. It is used to reflux hot liquids.

RENAISSANCE CHEMISTRY

Fractional distillation is a Renaissance innovation, but was initially very crude compared with more modern methods, largely because there is no obvious way of measuring the precise heat of a fire.

Distilling nitre with partially hydrated blue or green vitriol at high temperatures produces a substance called nitric acid. One of the uses for this substance is to separate silver from gold (the silver dissolves).

Adding nitric acid to sal ammoniac produces aqua regia, the only substance known which will dissolve gold. This is also used to separate silver from gold; the silver precipitates out of solution and is then recovered by smelting with alkali.

There are two new methods for producing soap. One involves a mixture of suet, stale urine and deer's grease and, while cheap, is not very popular.

By replacing caustic potash with polverine (the ash of certain woody shrubs) and using olive oil instead of tallow, it is possible to make much harder soaps with relatively little odour. It is possible to add perfumes to these soaps, and to use them for washing. Such soaps are a widespread luxury item.

The early sixteenth century also saw the invention of small sticks of wood treated with brimstone. These matches could be used as an alternative to flint and steel for lighting fires.