Vandyke Brown

Three brown pigments pass in commerce under the name of Vandyke brown. The first is made by calcining certain very ferruginous earths or brown ochres; the second is nothing more than a dark-brown variety of colcothar; the third is a kind of brown earth containing, along with some iron oxide and hydrate, a good deal of organic substance in the form of humus or bituminous matter. The first and second kinds are permanent and innocuous, but the third kind will not resist the prolonged action of light, becoming paler and redder in the course of time. The discrepancies in the published statements as to the permanence of this pigment are thus readily explained; it is to be regretted that most of the samples of Vandyke brown now met with in England belong to the third kind, and therefore fade quickly in water-colour, more slowly in oil. This sort may be recognised by the dark sublimate which it yields when its powder is heated in a test-tube, as well as by the change in colour and great loss of weight which it then shows.

We shall designate this less satisfactory variety in the Tables of Permanent and Fugitive Pigments in the present volume as Vandyke brown B., the other kinds being called Vandyke brown A. It is unfortunate that the colour-value of the perishable variety is incomparably greater than that of the more permanent sort.

Cologne or Cullen earth, and Cassel brown or Cassel earth, are soft, impure varieties of brown coal or lignite. They vary in fixity, some of them being even more easily bleached by light than Vandyke brown B.; these should not find a place on the palette of the artist. When slightly roasted, a part of the brown organic matter in these earths is charred or carbonized, and the substance becomes darker, duller, and decidedly less alterable by exposure. Some of the so-called Cologne earth now sold is merely Vandyke brown B., slightly changed by gentle roasting; it is then rather less alterable. We have met with some specimens of Cassel earth which proved practically permanent in oil, but even these faded quite distinctly when exposed to strong light after having been mixed with flake-white.