Reinforcing what Venning wrote, I quote from John Gage’s Color in Turner: Poetry and Truth:
By the standards of his time, when studio traditions of craftsmanship had all but ceased to exist, Turner’s sketchbooks are remarkably free from technical gossip; and Trimmer records only a single instance of the artist’s wish to discover the technical procedure of a contemporary: the oil vehicle of James Ward. In general, Turner seems to have been content to use the preparations of colormen like Newman, Middleton and Sherborn; and in view of the seven varieties of madder among the pigments at the Tate Gallery, and among the watercolors, it is notanble that he was asked by the Society of Arts as early as 1804 to test the qualities of a madder lake produced by Sir Henry Englefield.
Note, studio traditions of craftsmanship had all but ceased to exist. If someone has contradictory information I wish they’d supply it. I’m doing research, not trying to make subjective claims.
The next quote offers some insight into the radical nature of Turner’s experiments by the standards of his time:
Just after Turner’s death, John Burnet wrote that ‘the extreme vividness of his colours, especially when his pictures were fresh from the easel, arose from the chemical changes that took place in the manufacture of the pigments during his career, such as chrome yellow, emerald green, cobalt blue, &co,, which none had the courage to venture on but Turner.
Let’s also take a look at the reaction of one of the contemporary critics, completely unable to see what was plain in front of them, and clearly reminiscent of objections to all the later “radical” movements that followed. This is small wonder since many of those movements had their source in Turner’s apostasy. He liberated COLOR in ways that lit up the eyes and minds of painters toward the end of the 19th century.
The criticism of his day, later echoed again and again:
‘If the French fail in want of colour,’ wrote a critic of Ulyssses deriding Polyphemus in 1829, ‘this artist equally departs from nature in the opposite extreme. He has for some time been getting worse and worse, and in this picture he has reached the perfection of unnatural tawdriness. In fact it may be taken as a specimen of colouring run mad–positive vermilion,positive indigo, and all the most glaring tints of green, yellow and purple contend for mastery on the canvas with all the vehement contrasts of a Kaleidoscope or a Persian carpet.
The irony here, of course, is that it was precisely the French, seen in the quote as failing in the want of color, who charged ahead following Turner’s lead.