http://britishphotohistory.ning.com/profiles/blogs/nano-scientists-attempt-to-save-disintegrating-artworks?xg_source=activity

Quoted in full:

The recent article in the Scientific American magazine paints a picture of doom and destruction for daguerreian art pieces. Of course this is disconcerting for collectors and institutions that have significant investment in these beautiful objects. The author implies that degradation surrounding some Southworth and Hawes daguerreotypes in the Young America exhibition can be applied to all daguerreotypes when he writes “The vanishing images suggested that any daguerreotype could spontaneously crumble.” This sky-is-falling statement in my opinion does not represent the majority of daguerreotypes.
Lets review this issue.
Approximately 160 Southworth and Hawes daguerreotypes were exhibited over two years at three institutions. Five plates changed significantly with an obscuring white haze, and supposedly 25 plates changed slightly. The majority of the plates did not change at all.
From personal experience I can tell you that I have 19th century daguerreotypes as well as my own daguerreotypes that have been on continuous display on my studio for 10+ years with no sign of change. This is my argument against the claim that daguerreotypes are light sensitive.
What every collector or institution must know is Southworth and Hawes plates have a very unique storage history contrary to the norm. The great majority of S&H images that remain were plates retained by the studio stored completely unsealed in plate boxes. They were sold in this condition through Holman’s bookshop in the 1930’s. and early 40’s. As they migrated to private collectors and institutions they were sealed using what were thought of at the time to be proper conservation materials. A typical preservation package used by the George Eastman House from the mid-1970’s to 1999 consisted of 4-ply buffered board with a paper binding tape, and a buffered die cut paper mat separating the plate from the glass. The buffering agent is 3% calcium carbonate to provide an alkali reserve of ph 8.5.
A significant case in point. In 1999, a trove of Southworth and Hawes daguerreotypes were discovered in the garage of David Feigenbaum after his death. A team of conservation professionals from the George Eastman House were asked to prepare the plates for auction at Sotheby’s. Over 200 plates were housed in the materials described above. A collector who purchased a Southworth and Hawes daguerreotype from the David Feigenbaum sale brought it to me to replace the conservation housing with an 19th century brass mat, preserver and case. I retained the die-cut buffered mat and backing board. Soon after, I made a daguerreotype that I felt wasn’t good enough to frame in my own passe-partout housing design, but I wanted to preserve it as I had made it in collaboration with my friend Irv Pobboravsky. I placed the daguerreotype behind glass using the die-cut mat I retained from the Feigenbaum sale held together with spring clips and placed it in a zip-lock back. It was stored in the dark for approximately four years. It now has a very definite obscuring white haze adjacent to the mat. While this is not a scientific experiment, it does provide a significant observation and cause to question if the housing materials are contributing to the deterioration of the plates.
I have experienced the “white haze” phenomena on other of my contemporary images as well as on 19th century images that have been in contact with buffered board. What is good for the conservation of paper, ie alkaline buffering, is not necessarily good for daguerreotypes.
In reviewing the conservation efforts for the Young America Exhibition I learned that plates were not removed from their buffered mat board and die cut preservation packages. These were placed intact into extremely well sealed secondary housings incorporating shallow copper pans to act as pollutant scavengers. A complete overview of the conservation for this exhibition can be found here.
http://notesonphotographs.org/images/1/1e/Young_America_design_for_…
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.
In closing, I would say that daguerreotypes are among the most stable of photographic objects providing the housings are intact to prevent atmospheric pollutants from reacting with the silver surface and that the housings themselves are not contributing to the problem. The nature of the mechanism of deterioration particular to a small percentage of Southworth and Hawes daguerreotypes is not yet fully understood. The findings reported in the Scientific American article should not prevent us from exhibiting, collecting or enjoying these amazing photographs. It is prudent, as has been shown by the Young America exhibition, to accurately document any daguerreotype intended for exhibition and carefully monitor it at regular intervals to note any changes.
sincerely,
Mike Robinson
Daguerreian Artist
President of the Daguerreian Society

This certainly adds a new wrinkle to the previous Scientific American article. It also goes to show that just because an article comes from a reputable source does not necessarily mean it is accurate. My bad. This bears further following, and I will post updates as I find them. That said, I would still be careful in exhibiting Dags to prevent unnecessary degradation.