Points well taken, Jon.
Light-induced print deterioration is an accumulative experience, so there are many ways to ration the dose, and the Met's guidelines were just one of many suggestions as to how a collector might go about rationing the display time and keeping illumination levels to an absolute minimum (not always practical or enjoyable for the viewer). Although the most common way of expressing display life is by assuming steady state illumination and continuous uninterrupted years of display, the reciprocity law I described earlier (exposure = intensity x time) is simple linear math. So, you can accumulate the "allowable" exposure dose any way you deem appropriate. Of course, steps could also be taken to reduce the light intensity as the Met also suggested, but assuming that isn't possible, then print rotation or rationing the display time to some kind of amortization schedule is the other viable option. So, for example, if the curator does what the Met suggested, ie. put the artwork on illuminated display for only 3 months out of 12 and retires it to dark storage where no light fading will occur for the rest the year, then you'd get a factor of four times increase in "print life". But it's a not magic recommendation. Display a print only one month per year, and now you've stalled off light induced deterioration by a factor of 12! Getting even more creative, say you keep the print off exhibit for six years, now exhibit for six months, and there you go... you've achieved a one month per year light cycle that extends the print life prediction by a factor of 12 even though you had one six month exhibit instead of the Met's suggested 3 month limit. Once again, I stress the huge role of the collector in all of this print life prediction stuff. Reduce light levels, rotate sample locations and strive for lower light levels when and where you can, and you can have a huge impact on the life of the artwork! Light-induced fading is essentially straight-forward math for integrating the accumulated dosage over much longer time periods than one can achieve by constant illumination and constant time on display. In fact, the WIR and Kodak print life predictions already amortize their estimates in a fundamental way by assuming a day/night light cycle where no appreciable exposure is occurring for 12 out of the 24 hour daily time period.
When I was working at the Smithsonian Institution in Washington DC, I actually created a more sophisticated version of this pint life "amortization method" for photographs kept in cold storage. I called it "time out of storage" and the idea was to determine the effect of room temperature display on photographs that were otherwise kept in cold storage conditions. The reaction kinetics is a bit trickier than the simple linear math of the reciprocity law, but the amortization principle is the same. As a simplified example, imagine you had a Eutopian storage environment where all types of print deterioration stop 100% effectively, ie. the "fountain of youth". But leave the vault and the normal aging rate begins again. So, if you take a print out of the Eutopian storage vault for one month each and every year, then the best improvement in print life that the perfect storage vault can give you is a factor of 12. The print will not last "forever" as it would if the print always remained in the vault. Cold storage vaults thus can have tremendous benefits on longevity, but only when wise collection use policies are also put into place. Enjoying photos on display is indeed a consumptive pleasure. Nothing lasts forever, but again, as I have stressed in this whole discussion, if reasonable care is taken in our storage, handling, and display choices, then we have it in our power to make even the most fragile prints last a very long time. The time scale in and of itself is therefore not a particularly good bench mark for print permanence ratings, IMHO, but it took me a long time in my studies of print deterioration to arrive at that conclusion I must admit. The true benefit of the good lab tests is not to serve up "how long will it last" bragging rights. Rather, good tests advise and inform us about what the strengths and weaknesses are of a given process. Some are very sensitive to light, others to handling, others to air pollution, others to temperature and humidity, and still others to all of the above!
kind regards,
Mark
--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "piezobw" <jon@...> wrote:
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> Mark,
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> The MET once put out a small booklet which I remember was called How to Care For and Preserve Works of Art on Paper. From their point of view, a work of art be it a watercolor or a photograph or a pastel (this was pre-digital print) should not be subjected to more than 3 months a year exhibition at 50lux eight hours per day. It may have actually been much less.
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> Of course this small amount of exposure to light is extremely cautious on the part of an institution entrusted to preserve works of art for future generations. But, the pamphlet they published was intended to advise collectors for how to preserve works of art in private collections. Many of the private collections today are so vast that the caution was given to make sure collectors gave works a rest by cycling them.
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> I think it would be advantageous for Aardenburg to get that specific condition set from the MET, and to use that as one additional Conservation Display Rating. In some ways, collectors (especially the ones who acquire large amounts of photographs) have been left out of the WIR & Aardenburg ratings because the assumption is always that the work will be continuously displayed.
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> I've always thought that the only photographs that will ever actually be continuously displayed from their inception to the end of time are portraits of Popes in the Hall of Popes at the Vatican. Where else is anyone going to put up a framed print for 200+ years?
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> Because some very fragile processes may yet to be used by photographers, and perhaps because some very important photography may utilize very fugitive and unusual processes existing now - it would give confidence to museums and collectors to preserve more rarer forms of digital photography, that while not being capable of displaying well in a storefront display, would have an attractive display life in archive.
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> What are your thoughts on establishing a rating that would be of interest to curators because it was directly targeted to museum display conditions according to their archival policies?
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> Just to be sure I've distilled to you what I am trying to say - I understand that you currently have a "Museum Standard" of 50 lux 12 hours per day. But, that assumes continual display which is not likely in a museum. My question is rather in regard to the policies of how a museum keeps a single work of art over its entire expected life span according to their policies (storage in dark, occasional exhibitions, etc.)
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> Jon Cone
> Piezography
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