I don't think it would be a stretch if it was discovered that the use of camera obscura to be more prevalent than previously thought - we await time travel... Van Eyck and many other artists have fascinated me with their expertise and skill. Use of camera obscura would bring their art closer to human scale - though still well outside my range without a lot more practice and imagination. Wouldn't that also add the photographic perspective?
I'm not clear what you're suggesting regarding something of a chemical nature? Some of the techniques he used - oil paint... multiple translucent glazes... tools to enhance details... and use of light to enhance depth, etc. The oils and glazes are certainly of a chemical nature,... am I missing something more?
What if some painters were using something of the following nature to sketch over before painting. The following notes are for an article I never published due to experiments that were not successful (pictures not copied into post) : -
The elusive leucotype
Within the history of photography there were many different chemical formulations which were capable of reacting to light. Some of these could be stabilised or fixed after exposure and some could not. There are probably others that were never brought into practical use after the Calotype and Daguerreotype became established processes.
I would like to draw attention to a little-known process that Fox Talbot discovered in 1840 in which I believe was a response to a desire to develop a direct positive process to presumably compete with Daguerre. He was not alone in experimenting with a direct positive process, as others such as Robert Hunt, Hippolyte Bayard, Dr Andrew Fyfe and Jean Louis Lassaigne in France were among others, experimenters of that era.
Just prior to developing the Calotype (the first practical negative/positive process), Talbot experimented with a chemical means to create a positive image, presumably because he had not fully realised the full potential his repeatable printing process had for multiple copies of prints. Something that the Daguerreotype could not do, being a one-shot process. He succeeded in producing direct positives with a process utilising Silver Nitrate and Potassium Iodide and called these images Leucotypes. The name is derived from the Greek word Leuco, meaning white.
The process Fox Talbot developed, was basically to darken his photogenic paper in sunshine and then apply potassium Iodide, after which he could produce a positive photogram effect with objects placed on the paper in sunshine. He called it a Leucotype , but didn’t patent it with that name, as it appears in patent number 8842 on the 8th February, 1841 along with 5 other process applications.
The reason I think it is worth exploring the Leucotype in greater detail is because when we look at it in its historical, chronological context, it was only 2 days later Talbot was to discover how the use of Gallic acid had the potential to develop a latent image. A discovery so important in the History of photography that it makes the discovery of the Leucotype pale into insignificance in the race to produce a practical photographic process. If I could draw an analogy, it could be a bit like discovering a propeller to power a plane and then discover the jet engine. So, let’s step back in history and look at Leucotype chemistry in greater depth.
Letter from hunt – investigate – very important
My own experiments in this process were very limited, but thought it worth mentioning, as others may wish to explore this process in greater depth.
To make a Leucotype is a fairly simple process, which involves coating paper with Silver Nitrate, fogging it in sunlight and then recoating it with Potassium Iodide prior to exposing it in contact with some image material, as in a photogram situation. The initial low sensitivity of these Leucotypes made them difficult to use in a camera. However, he did find through experimentation that changing the strength of the potassium Iodide in relation to the strength of the silver nitrate did increase the sensitivity. This was recorded in his notes on the 18th September, 1840. He also found that it could be fixed or stabilised, just by simply washing it in hot water. But what makes the lectotype even more interesting is that ******** >I’
Reference dates in Talbots notebook Q to Leucotype –
Sept 17/18 1840
27 Feb/5mar 1841
20 Apr and 5 may 1841
may/Sept !841
Sept 4 1842
Oct 7 1842 – March 1843
March/April 1843
Q37 – common photogenic paper blackened in sun, place object on its re-expose in sun, the exposed part will turn green, then wash with potassium iodide and put in light. The black part is whitened and the green blackened.
Q75 – curious anomaly. Some specimens of leucotype paper are not partially whitened by a very short exposure, but darkened. A longer exposure however lightens them.
Curiouser and curiouser said Alice.
Test exposures under glass
Q75 – Paper dipped in nitrate of silver very strong and then in iodide potassium of moderate strength turns brown in light, or when warmed. This browned paper washed with prussiate potassium is whitened. This whitened paper is very sensitive to light.
Positive prints may be made on this dark paper, viz by washing it with prussiate potash after the picture has been received, which whitens the part acted on by light much more than the light itself has done.
