Technique and condition
This etching in warm brown ink on medium weight off-white wove paper has been worked up by Turner with warm monochromatic washes of watercolour in a similarly warm brown tonal range. The visual effect is closer to an engraving with aquatint than to a watercolour sketch made for latter engraving, and Turner did not often experiment with this combination of techniques on the same sheet of paper. It is a relatively deep bite etching as seen by the raised ink on the recto and mirrored indentations on the verso. These marks form the outline, definition and depth of the images while the watercolour forms subtle and loose washes over the rest of the support.
Some materials analysis was carried out, using a tiny sample of paint and ink removed from heavy applications that run right out to the sides. The very heavy printing of the etched lines made it possible to lift a sliver of ink clear of a line, while leaving most of it behind on the paper. Such a microscopic sample of printing ink can be flattened out for characterisation of its binding medium by a technique know as Fourier transform infrared microscopy, which involves shining infrared light through the sample and comparing the results with those from known historical materials, or modern reconstructions of historical recipes for artists’ materials. This indicated that the printing ink is oil-based. There is no sign of the yellow staining that often surrounds oil paint applied with a brush: printing ink is more viscous and it is intended to dry fast to avoid just this problem – which means that its component materials cannot be identified reliably by eye. Turner habitually used additions of varnish to oil paint to create thick, gelled paints that would be capable of forming similar-looking printed lines, but here the choice of ink was entirely conventional for work with an etched copperplate.
The same tiny sample could be retrieved and placed in the sample chamber of a scanning electron microscope in the path of a beam of electrons, which are scattered off the sample in a technique called energy-dispersive X-ray analysis, that leads to information on the elements used in the pigments and other components of the ink. Here it can be inferred that bone black (calcium phosphate) and umber (an iron-based earth pigment with manganese oxide incorporated) were used, which is the simplest possible mixture that would create a deep warm brown ink. Printers would mix ink from a range of earth pigments including ochres and umbers, blacks, and bright red vermilion to give warmth: all of these constituents have been found by analysing a small number of other suitable etchings and engravings which belong to the Liber Studiorum as does this work.
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