NATURE 



24] 



THURSDAY, JANUARY 14, 189: 



THE CHEMISTRY OF PAINTS AND 

 PAINTING. 

 The Chemistry of Paints and Painting. By A. H. 

 Church, M.A., F.R.S. (London : Seeley and Co., 1890.) 



CONSIDERING the widespread interest which at- 

 taches to all matters connected with pictures and 

 painting, it is perhaps somewhat surprising that up to 

 within quite recent times no attempt has been made to 

 discuss and review in a comprehensive and efficient 

 manner the materials and methods of painting from a 

 strictly chemical point of view. It will, however, be 

 readily conceded that the field is an extensive one, and 

 it is, moreover, obvious that an intimate acquaintance 

 with the technique of painting will be found only very 

 rarely associated in the same individual with a thorough 

 knowledge of chemistry. Neither a mere chemist nor a 

 mere artist could undertake the task with a fair prospect 

 of success. 



The author of the present volume, on accepting, some 

 years ago, the Professorship of Chemistry in the Royal 

 Academy of Arts, found there a congenial sphere of 

 activity, and an opportunity of devoting himself thence- 

 forward to chemistry in its bearing on pigments and 

 painting — a subject which long before had had a great 

 attraction for him, as evinced by his early publication 

 referring to these matters, and also by the fact that he 

 has himself practised with no inconsiderable success the 

 art of painting. It is thus that the information given in 

 this work is derived on the one hand from an exact 

 scientific study, whilst on the other hand it is based upon 

 a knowledge of the technical details of the art. As it 

 has been written especially with the view of explaining to 

 the artist and the art student the more important chemical 

 and physical characters of the materials they employ, 

 and of the processes they manipulate, the author has 

 exercised commendable discretion in not encumbering 

 the text with chemical detail beyond the general scope 

 of those for whom the book is intended. 



" In many instances a sketch of the processes for 

 preparing certain pigments and varnishes is given, 

 not in order to turn the painter into a colour-maker or a 

 varnish manufacturer, but rather that he may acquire 

 a clearer insight into the nature and properties of the 

 most important constituents entering into the composi- 

 tion of his pictures." 



The author very aptly begins his work by a discussion 

 of the various painting grounds, and briefly describes the 

 essential qualities of paper, vellum, ivory, fresco and 

 stereochrome grounds, of slate and stone, of wood panel 

 and canvas. This part is divided into four short 

 chapters, which contain many valuable practical hints. 

 He next proceeds to the description of the vehicles and 

 varnishes, and this part comprises the oils, resins, waxes, 

 paraffin waxes, yolk and white of ^g-g, size, glue, gums, 

 glycerine, honey, water-glass, lime and baryta-water, 

 solvents and diluents, siccatives and dryers, varnishes 

 and oleo-resinous vehicles. 



Describing the several drying oils— namely, linseed oil, 

 poppy oil, and walnut oil, he enters more fully into a 

 NO. 1 1 59, VOL. 45] 



discussion of the first-named as being the typical one, 

 and also by far the most important. Here he gives an 

 account of the proper mode of preparing and purifying 

 the oil, and directs attention to the variation of the 

 qualities of the oil of seed of different origin ; he also 

 explains why preference should be given to the cold 

 pressed oils. A very concise and instructive discussion 

 of the chemical composition of linseed oil leads on to 

 a consideration of the chemical change which the oil 

 undergoes in the act of drying. This remarkable change, 

 in which the chief value of these drying oils centres, is 

 greatly accelerated by the presence of certain metallic 

 oxides, such as those of lead, iron, or manganese. Later 

 on, in a chapter devoted to siccatives and dryers, the 

 author directs attention to the excessive and improper 

 use of lead compounds, and very justly refers to the 

 advantage of using instead of them the compounds of 

 manganese, and especially the borate, in the preparation 

 of the strongly drying oils. Such delusive dryers as 

 borates of lime and zinc or sulphate of zinc, however, we 

 think ought to have been mentioned only in order to 

 condemn them. 



The chapter on resins, waxes, and solid paraffin, con- 

 tains a description of these substances and their properties 

 in so far as they are of interest to the painter. In a 

 similar manner the author treats the various other 

 materials considered in this part, such as yolk and white 

 of Qgg, size, gum, glycerine, water-glass, &c. ; and under 

 the head of solvents and diluents we find a very useful 

 and instructive account of the different kinds of oil of 

 turpentine and the liquid hydrocarbons made use of in 

 the artist's studio. Amongst them, oil of turpentine 

 stands foremost in importance. It is to the painter in 

 oil colours what water is to the painter in water colours ; 

 and in order to fulfil its function in the most perfect 

 manner, it is essential that it should be pure, and should 

 completely volatilize without leaving any phlegma in the 

 substance of the paint. Oil of turpentine is very prone 

 to become changed and acted upon by the atmospheric 

 oxygen, especially in the presence of moisture and under 

 the influence of light. As the author points out, different 

 kinds of oil of turpentine vary very materially in this 

 respect, and the artist has to be on his guard to select 

 the best kinds for his use. The employment of de- 

 teriorated or inferior oil of turpentine may give rise to 

 very serious defects which are often ascribed to other 

 causes. Other hydrocarbons, now available for the artist, 

 are petroleum spirit and the benzenes, which comprise 

 liquids of very varied degrees of volatility, and which do 

 not share the objectionable propensity of oil of turpen- 

 tine just alluded to. Here we would, however, remark 

 that the petroleum hydrocarbons are much less efficient 

 solvents than oil of turpentine, as they do not entirely 

 dissolve even mastic or dammar ; whilst, on the other 

 hand, the benzenes are much superior in this respect, 

 and especially the higher members of this series deserve 

 the attention of the artist and varnish maker. 



The last chapter in Part II. discusses varnishes and 

 vehicles, their composition and preparation. Treating 

 of mastic varnish — which is merely a solution of mastic 

 in some volatile solvent, generally oil of turpentine — the 

 author assigns to this substance its proper function, 

 which is that of a surface varnish only. On no account 



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