I haven’t been making colored Daguerreotypes lately but a few years ago I did some experiments on the effects of various copper and iron salts on heliochromes. In the Burder and Niepce de Saint-Victor process the plates are coated in a solution of ferric chloride and copper sulfate. I found that copper chloride, also worked to a limited degree. At least the silver chloride was formed on the surface.
Plates coated in iron chloride solutions tended to form more reddish flag images whereas plates coated in copper chloride solution formed fainter reds and blues.
Plates coated in a solution containing both ferric chloride and copper chloride together or both salts applied sequentially in separate solutions tended to reproduce the colors of a Kodak Q60 Target slide better than did a solution of ferric chloride alone. The Q60 Trans was very thin. Therfore the exposures required were only 20 min in direct sun The colors produced appear to depend upon the presence of water soluble Iron and copper salts trapped in the insoluble silver chloride matrix and can be washed out with water in 24 hours leaving the silver chloride behind.
Approximately 3-4 years ago I did make and keep 4×5 heliochromes prints of Burder’s high density Fruit bowl transparency. They were made by coating silver plates for 3 minutes in 3.0 or 4.5% FeCl3 solutions which also contained 2.2 or 2.6% CuSO4 respectively followed by a 5 second rinse in distilled water. Longer contacts with water both before and after exposure were avoided. Burder’s fruit bowl transparency was very dense. Therefore exposures of 12 hours in direct summer sun were required. Since then the plates have been kept in the dark in glass plate holders. except for brief periods of examination. They have shown very slight signs of fading.
However when the plates were fixed in a solution of sodium thiosulfate, the colors completely disappeared, leaving a positive Daguerreotype image.
I have images of all my heliochrome work but I was unable to attach them here.
