The whole page is taken up with notes on chemistry in relation to colour:
Lac. 1 part of Borax to 5 of Lac | renders the whole soluable by digestion in water | at a boiling heat This solution is nearly equall | to Spirit Varnish
Litharge fuzed with common salt | Decomposes, the lead forms with the muriatic | soln yellow Patent yellow
according to Beckmann. is calcined Lead | with antimony and Potash in a reverb[...]y furnace | ant 4/5 of L P 2/5 of the whole. sometimes Salt
Joyce Townsend does not establish the origin of these notes, with a recipe for ‘white lac varnish’ and concerning the ‘production of yellow inorganic pigments, patent yellow and Naples yellow’.
1This is one of fourteen pages of notes on varnishes and colours resulting from chemical reactions between folio 62 verso (
D09974) and folio 55 recto (
D09959), working from the back of the sketchbook as now foliated. Thornbury noted ‘Naples yellow’ among his potted transcriptions from these passages.
2 As discussed in the sketchbook’s Introduction,
3 most are taken from William Nicholson’s 1808
Dictionary of Practical and Theoretical Chemistry., beginning here with part of the unpaginated entry on ‘Lac’:
The colouring matter is soluble in water; but 1 part of borax to 5 of lac renders the whole soluble by digestion in water nearly at a boiling heat. This solution is equal for many purposes to spirit varnish, and is an excellent vehicle for watercolours, as when once dried water has no effect on it.
The second paragraph is taken from the entry on ‘Lead’:
Litharge fused with common salt decomposes it; the lead unites with the muriatic acid, and forms a yellow compound, at present used in this country as a pigment, for which an exclusive privilege has been granted.
Incidentally, this yellow pigment is also referred to in more detail in Nicholson’s entry on ‘Acid (Muriatic)’:
From this salt, as already observed, the muriatic acid is extracted; and of late years to obtain its base separate, in the most oeconomical mode, for the purposes of the arts, has been an object of research. The process of Scheele, which consists in mixing the muriat of soda with red oxide of lead, making this into a soft paste with water, and allowing it to stand thus for some time, moistening it with water as it gets dry, and then separating the soda from the muriat of lead by lixiviation, has been resorted to in this country. A Mr. Turner some years ago had a patent for it; converting the muriat of lead into a pigment, which was termed mineral or patent yellow, by heating it to fusion. The oxide of lead should be at least twice the weight of the salt. This would have answered extremely well, had there been an adequate and regular demand for the pigment.
The patent Nicholson mentions was granted to James Turner in 1781, for ‘A Method of Producing a Yellow Colour for Painting in Oyl or Water, Making White Lead and of Separating the Mineral Alkali from Common Salt, All to be Performed in One Single Process Which Would be of Great Publick Utility’.
4 Townsend has noted J.M.W. Turner’s use of patent yellow
5 in his oil painting
Dido and Æneas, exhibited at the Royal Academy in 1814 (Tate
N00494).
6Turner’s last paragraph takes its heading from Nicholson’s entry on ‘Naples Yellow’:
According to prof. Beckmann this colour is prepared by calcining lead with antimony and potash in a reverberatory furnace. The proportions are different, but the antimony appears never to exceed four fifths of the lead, or be less than half: and the potash varies from two fifths the weight of the metals to an eighteenth. Sometimes too common salt is added. – Beckmann Hist. of Invent.
Nicholson cites the German scientific writer Johann Beckmann (1739–1811) and his History of Inventions and Discoveries, published in English in 1797.
