24 APRIL 1886, Page 23


The At tistd' Manual of Pigments. By H. C. Standage. (Crosby Lockwood and Co )—Too little is known by the modern artists of the chemical nature of their paints, whereas, in the time of the old masters, every artist had to grind and prepare his own colours. Although chemistry was then in a most elementary state, he had perforce to know something about the reactions which occur between certain mixtures of pigments. This enabled him to know what was safe to use ; it prevented him from ruthlessly mixing colours which in time destroy each other, and saved him from cheap and adulter- ated paints. This little manual cannot fail to be a very valuable aid to all painters who wish their work to endure and be of a sound character ; it is complete and comprehensive. The chemical nature and qualification of each colour in its perfect form is given, also the simplest mode of testing their purity. The use of the blow-pipe, which is recommended as an easier means of analysis than what is known as the "wet process," where it is desired to know what metal the pigment is a salt of, could no doubt be practised after the simple explanation here given ; but all the same, we advise any artist who wishes to use this test, to see if he cannot get some chemical friend to put him in the way, as there is a knack about it which can be more easily shown than described. The paragraphs on permanency and non-permanency are exceptionally useful, and following up the account of the chemical names and composition, enable the artist to judge what colours may be safely used, either alone or in combination with others. For instance, white lead affects many colours deleteriously, impure air others ; again, there are some colours paled by light ; cobalt and gamboge slightly chrome to a great degree ; Prussian-blue loses its colour with light, but darkness restores it ; while Indian-yellow is affected by darkness and obscurity, and remains unchanged in light, or even strong sun. Then there are some colours whioh are valuable in water-colours, but un- stable in oils, and, again, vice versa. Then many colours, when pure and unadulterated, stand ; but where impure, become unstable in various ways, according to the adulteration. Among the reactions which are the most destructive to the permanency of the painting, are those which occur between pigments possessing a lead base and those where sulphur is a component part. " Briefly, the action is this,— lead possesses a great affinity for sulphur, consequently these two elements forsake the other components of their respective pigments, unite and form a new compound—sulphide of lead—which is of a black hue." To take an example, red vermilion (which is a red sulphide of mercury) when mixed with chrome-yellow (a yellow chromate of lead), these two colours will produce an orange hue; " but as soon as the sulphur in the vermilion unites with the lead in the chrome - yellow, we get the black particles of lead- sulphide produced, and these commingling with the yellow and red particles of the above pigments, change the orange hue into an auburn or brown hue, or to a brownish red, in proportion to the amount of black particles proportionately to the yellow and red ones. Take another case of this visual physical change. Say a lead-chrome is mixed with artificially made ultramarine, and that there is some free sulphur in the ultramarine (i e., that this pigment has been care- lessly made, and consequently not entirely freed from this sulphur). The mixture of the yellow and blue will produce a green ; bat in time, as the free sulphur unites with the lead in the chrome, black sulphide of lead appears, and we then get yellow, blue, and black particles hetero- geneously mixed, with the result that the visual impression pro- duced by these three colours will no longer be the bright green formed by the blue and yellow, but will be a dark green approaching

black." These few examples will suffice to show the importance of some study of the chemistry of colours. It is possible that in some details we may find some slight difference in opinion among colour-chemists, now that their attention is more turned to the study ; but in all the broad, main facts, we may be sure that they will agree, and we could not do better than advocate the study of the science of Mr. Standage's little manual.