decayed daguerreotypes/

[M Carter]

Found this oddly beautiful and spooky...

http://publicdomainreview.org/2013/01/08/decayed-daguerreotypes/

 

[BrianShaw]

Very interesting. Thanks for sharing that find with us!

 

[AgX]

the glass itself can also deteriorate and bubbles of solvent explode upon the image

Well...
But I admit deterioration other than caused by rubbing of any kind has been reported and is researched on in Rochester.

 

[BrianShaw]

There are several good (academic) books on dag deterioration and restoration. If anyone is interested I can give citations later. IDK about glass deterioration and solvent bubbles... never heard of that. Most of my dags (and those in the link) show silver oxidation (tarnish) more than anything else. I have one that someone tried polishing with silver polish... it's a complete mess.

 

[Photo Engineer]

There is a very extensive project at George Eastman House investigating this deterioration. The phenomena involved are not well understood.

PE

 

[falotico]

Daguerreotypes had a metal base, typically copper, which had a silver coating on top, if I remember correctly. The silver was immersed in halide fumes, typically iodine, forming light-sensitive silver halide crystals on the surface of the photograph. This was next placed in the camera and exposed to the image produced by the lens. This exposure could be as long as 15 minutes.

To develop the daguerreotype the exposed plate was placed in a dark box over a dish of liquid mercury which was heated by an alcohol lamp or a candle. Heated mercury fumes would bombard the plate. Wherever the plate was exposed to light the silver halide was converted to pure silver metal. The mercury atoms would stick to the pure silver metal and form an amalgam, (this process was known since the Middle Ages). The amalgam was lighter in color than the unexposed silver halide, so wherever light struck the plate it would appear lighter in color than the unexposed parts. Therefore daguerreotypes were a direct positive process which usually produced a mirror image.

Considering that the image layer of a daguerreotype contains silver, silver halide, mercury, mercury silver amalgam and copper it's a wonder that more daguerreotypes do NOT tarnish. There are so many chemically reactive metals touching each other it is hard to see how the system could be stable.

 

[BrianShaw]

IDK about the chemistry and associated stability, but the better sealed they are the less they tend to tarnish.

 

[Photo Engineer]

At GEH they are making glass frames that can contain a Daguerreotype under an inert atmosphere so as to preserve them. It does appear that air and air pollutants are involved, but again, no one seems to know the mechanism and no one knows how to restore one AFAIK.

PE

 

[AgX]

The amalgam was lighter in color than the unexposed silver halide, so wherever light struck the plate it would appear lighter in color than the unexposed parts. Therefore daguerreotypes were a direct positive process which usually produced a mirror image.

The silver halide is fixed out. The amalgam thus has to compete with still polished silver in the end. Something only possible if there is no specular reflection from the silver but diffuse reflecttion from the amalgam. Thus the process is a lighting dependant direct-positive process.

 

[falotico]

Did they use thiosulfate or cyanide compounds to fix daguerreotypes? Or was some other method used to remove the silver halides?

 

[BrianShaw]

At GEH they are making glass frames that can contain a Daguerreotype under an inert atmosphere so as to preserve them. It does appear that air and air pollutants are involved, but again, no one seems to know the mechanism and no one knows how to restore one AFAIK.

PE

Have you seen Barger and White, The Daguerreotype; Nineteenth-century technology and modern science, 1991? It addresses some of those issues plus restoration. I think it might be yoru kind of book... lots of science and technology.

 

[dmschnute]

There is an article in the December 2012 "Scientific American" describing a similar occurrence. Apparently a collection of daguerreotypes from GEH began to decay almost as soon as they were placed on exhibit in New York City. The article theorizes a possible cause as well as a strategy to protect them.

 

[Photo Engineer]

Guys;

I am not involved in this project at GEH. I have talked to the lead investigator many times and some of our work is done in the same labs. I feel uncomfortable about discussing this work any further as it is not mine and I am only peripherally aware of it.

PE

 

[TheFlyingCamera]

There is an article in the December 2012 "Scientific American" describing a similar occurrence. Apparently a collection of daguerreotypes from GEH began to decay almost as soon as they were placed on exhibit in New York City. The article theorizes a possible cause as well as a strategy to protect them.

The SciAm article is problematic in that it does not adequately address a potential cause of the problem, namely the materials used in storing the plates.

http://britishphotohistory.ning.com...ve-disintegrating-artworks?xg_source=activity

Dead Link Removed

If the buffered materials are a co-factor in the formation of “white-haze” deterioration it would explain why even with the best intentioned conservation, some plates still changed during exhibition. A questionable environment was enclosed within a stable one.
This remains to be explored and I hope to soon analyze the plate and mat from my example. I present this scenario as a possible alternative and/or co-factor to the silver-chloride scenario presented in the Scientific American article.

There is no proof that this is an endemic problem to Daguerreotypes, and plenty of anecdotal evidence that there is an external primary contributing factor. Given the age and irreplaceable quality of daguerreotypes, it is better to proceed with caution, but we should not panic a-la Chicken Little and presume this will be the eventual (and proximate) fate of all daguerreotypes. As PE has stated, further research is needed to determine the specific and exact causes along with prevention and remediation methods if possible.

 

[BrianShaw]

I'm still in the process of getting a copy of the article so the answer to my question may already be printed, but were the dags displayed in their orgiinal cases?

I have a collection of Dags, most in their original cases and even those with the seals unbroken there has been increased deterioration. All in dark, cool storage for about 30 years with viewing on rare occasion. Most of what I see appears to be the routine tarnish growth from edges to center... not "white haze", which I've never heard of before this.

 

[TheFlyingCamera]

The Southworth & Hawes dags were for the most part never in cases originally - they were kept in plate boxes, unmounted, until well into the 20th century. They were then mounted into what was considered to be the most archival preservation materials at the time - buffered mat board, glass and tape. The full details are explained in the links I posted.

 

[BrianShaw]

Thanks. Will check out those links ASAP.