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Lake Pigments
This important class of pigments has seen great developments in recent years.Originally, the name was applied to pigments or dyes derived from various plants, woods, and insects, as, for example, madder roots, logwood, and cochineal, but nowadays it has a far wider application and includes pigments produced by striking dyes or transparent pigments upon inert bases, such as alumina, barytes, blanc fixe, orange lead, or zinc oxide.
Most of the natural lakes are now obsolescent and the great majority of lake pigments are prepared from artificial dyes.
The natural lakes still produced on a limited scale include:
Carmine.- This brilliant colour is derived by steeping the dried cochineal insect, collected from the leaves of certain cacti in South America and Mexico.
It is insoluble in water, turpentine, or oils but soluble in alkalis, in which its colour deepens.
It can be ground in oil or water, but has no permanence and fades badly after a comparatively short period of exposure.
Crimson Lakes, Scarlet Lakes, are prepared from cochineal precipitated on alumina.
Although the colours are rich and brilliant, they are extremely fugitive and should not be used for any paint likely to be sub jected to the rays of the sun.
Madder Lakes.-These are derived from colouring matter found in
the roots of the madder plant (chiefly the Rubia tinctoria, but also one or two other varieties). They are remarkable for their brightness and also for their fastness to light.
Though still used to a certain extent by artists, natural madder lakes have been superseded by artificial alizarine so far as paints for decorators are concerned.
Indigo.-This deep-blue pigment is derived from a variety of plants grown in India and the East.
It has strong tinting properties but lacks opacity and is not fast to light.
Very little of the natural indigo is now prepared but it still finds some use as a pigment for artists.
Yellow Lakes.-A range of yellow lakes is prepared from various trees, plants, and flowers.
The most important, so far as the decorator is concerned, is that known as Dutch Pink, sometimes called Italian Pink.
It is made by colouring a white base, such as Paris white, with a decoction of quercitron bark, procured from a tree which grows in South and Central America, and in the USA. One of the uses of this pigment is as a glaze for subduing the brightness of a colour, as when, for example, it is desired to match paintwork which has faded.
Artificial Lakes
The great majority of lake colours now in use are prepared from synthetic dyes, precipitated on to suitable bases.There are many hundreds of these dyes, covering practically every colour, and their manufacture is a highly complex process.
As with most other products, the quality varies considerably, but the best lakes made artificially are remarkably permanent and give excellent results.