Quote Originally Posted by dmschnute View Post
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/...ource=activity

http://notesonphotographs.org/images...ign_for_&#8230

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.