…and another red: brazilwood

Brazilwood:

Origin: Brazilwood dye comes from the Caesalpinia tree, and was named “brazil” even before the discovery of that country!

In the Middle Ages it was always sold in blocks, and the craftsman had to reduce the solid wood to powder by scraping it with a piece of glass, or filing or pounding, as the finer the powder the more easily the color can be extracted from it.

In its natural state, brazilwood is a light, brownish red; mahogany in appearance. Today it is sold in blocks or chips, and sometimes in scrapings or shavings (as of 1960s).

Pigment: When the brownish powder of brazilwood is wet it turns reddish. When steeped in a solution of lye it colors the liquid deep, purplish red, and hot solutions of alum extract the color from the wood in the form of an orange-red liquor.

Most medieval brazil lakes were made either from the extract made with lye (a weak solution of potassium carbonate) or from the alum extract, as these solutions get the color out of the wood more thoroughly than plain water. Just what the shade is that is extracted depends on how acid or alkaline the mixture of solutions is made. The more alum: the warmer the color, the more lye: the colder the red. The precipitate is collected by settling and pouring off the liquid. The pasty mass is smeared on an absorbent surface such as a new brick or tile to dry. Then it is ground, and has the same degree of transparency as the alumina of which it is chiefly composed. When chalk is added to the alum, a more opaque pink rose is produced by the resulting admixture of calcium sulphate to the alumina lake. When white lead was used, it had no other effect than to give substance to the lake and slightly less transparency, rather than to make it opaque. When marble dust and powdered egg shells were added to newly formed lakes, they further controlled the color produced by reacting chemically with any excess of alum which might give a brown cast instead of rose. In all these cases the brazil color was mordanted upon the white material, so to speak, dyed with the brazil, and the pigment so formed was different from a mixture of a finished lake with a white pigment. 

In art: Brazil lakes are not very permanent.

Reference source: http://jcsparks.com/painted/pigment-chem.html#Brazil