…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

Richard Of York Gave Battle In Vain: colour pigments

Let’s start with red, or should I say reds….

red, the color of blood, fire and wine….. life, danger and vitality

Alizarin crimson (Alizarin madder lake)

About: Madder lake was made from the European madder root, Rubia tinctorum.  Since the 1850s (approximately) it has been made synthetically– under the name alizarin– with an identical chemical composition, but a superior clear transparent tone and lightfastness and by manipulating these chemicals, a range of shades has been made from scarlet to ruby.

Pigment: Roots of the madder plant are dried, crushed, hulled, boiled in weak acid to dissolve the dye, and fermented to hydrolyze anthraquinones from the glycosides. The extracted dye is made into a pigment by dissolving the dye in hot alum (aluminum potassium sulphate; AlK(SO₄)₂ · 12 H₂O) solution, and precipitating pigment with soda or borax. Synthetic alizarin lakes are prepared by reaction of alizarine with aluminum hydroxide.

 In art: Alizarin lake colors are permanent to light and to the gaseous atmospheres of urban areas. However, when mixed with ochre, sienna and umber, they lose their permanence, and when mixed with blacks or oxides, their permanence is not affected at all. Excellent as a glazing color over a dry surface. Alizarin madder lake  is a coal-tar color, and in permanence exceeds the natural product, which in contrast ages more gracefully than the artificial.

For more information see http://jcsparks.com/painted/pigment-chem.html