Robert A. Boal
Blue tone photos
I found an album that has photos from about 1900. They are blue. Was there a blue type of photo finishing or have the black photos faded to a blue shade? We have other photos taken by the same photographer and they have remained black.
We would appreciate any insight you copuld share regarding these pictures.
|Alan N. Marcus||
As you know photography was and remains to some extent a chemical based business. The film and photo print was based exclusively on silver. To make film and paper the metal silver is compounded with one of three elements, these are members of the halogen family (salt makers). The three are iodine, chlorine, bromine. The silver salt of iodine is the least sensitive to light and used to make slow contact papers. Silver chloride is generally used to make enlarging papers where higher sensitivity is required for projection printing. Films are mainly silver bromide for higher ISO speed. Any and all can be made up of blends of two or more salts of silver. These salts are crystalline.
When exposed to light the bond that holds the silver to the halogen is weaker. A latent image (one that has been exposed but not developed show no trace of an image until developed.
The exposed film or paper is immersed in a developer solution. The developer seeks out those silver crystals that have been exposed to light and reduces them. Reduction is the splitting of the crystal into its two component parts. The magic of the developer is its ability to recognize exposed vs. unexposed crystals. Unexposed crystals remain intact. The two component of the now reduced crystal are silver and a halogen. The halogen is water soluble and dissolves away in the waters of the developer. Tiny flakes of metallic pure silver remain imbedded in the gelatin.
The film or print is immersed in a weak acid (vinegar) called a stop-bath this halts development. Next the film or paper is immersed in a fixer solution. The fixer is a solvent for silver salts but not a solvent for silver. The result is the finished print contains only pure silver flake imbedded in gelatin. The film or print is washed in running water to remove residual chemicals and then dyed.
The black and white image is white in locations void of silver, black in locations laden with silver and shades of gray are produced in intermediate areas.
The silver based print is prone to tarnishing. Silver combines with sulfur and forms silver sulfide a yellowish brown compound. Likely the tarnish takes place over time due to exposure to air pollution and airborne sulfur was prevalent in the first half of the 20th century due to heavy reliance on burning coal. Such tarnish is unsightly and uneven.
Photographers often pre-tarnished prints for permanency. Silver sulfide is inert thus the image will outlive the paper. The brown sepia tone that resulted is pleasing. Toning was a common added step in the photo lab. Toning combines something with the silver or replaces it altogether to make the print more enduring. Toning added color that was considered pleasing; after all it was a black & white imaging world.
Blue tone was produced by the chemical Prussian blue ferric Ferro cyanide (not poisonous). The image is bluish, not as inert as the sulfur based tone but many liked the blue and considered it a touch of class.
Alan Marcus (marginal technical gobbledygook)
John H. Siskin
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While the image in a cyanotype is in fact Prussian Blue it is not a silver based image. The standard formula for a cyanotype is made with Potassium Ferricyanide and Ferric Ammonium Citrate. The image is not a toned image but is actually iron based ( thatís the Ferric Part). This was a popular method of making prints at the turn of the century. It is both inexpensive and relatively permanent. I have a couple of cyanotypes from just after 1900. I have also made cyanotypes. The process was introduced by Sir John Herschel very early in the history of photography. Since it was also used for commercial blue prints it is the print process that was used for the longest continuous time. It is still used by alternative process people today. I am including a copy of a cyanotype with this post. Please keep in mind that seeing an actual print is different from what you see on the screen.
There is a blue toner, but it would not have been used in 1900.
|Alan N. Marcus||
Hi Robert & John
I considered that the blue toned prints in the album were indeed Cyanotypes of the Sir John Herschel process. Sir Herschel invented the process in 1843 however it did not become popular until 1880. I do not know how long thereafter it was retained in popular usage. Additionally, most Cyanotypes I have seen are somewhat more intense blue than a blue toned print. I would think that someone coming accross a collection of Cyanotypes might describe them as blueprint-like as opposed to blue-toned.
I suppose some knowledgeable person will see the prints and make a determination.
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