RE: preservation of negatives/slides/prints
Don't have time to get into details, but the way the film was made, including the formula for the "film dope" and the way it was filmed has some influence on the stability of the film as well. Acetic acid is a relatively weak acid compared to the degradation product of common plasticizer, triphenyl phosphate (degraded into diphenyl phosphate). Plasticizer is present at about 1:10 in acetate film and it's a lot. So the name is "vinegar syndrome" but the reality is probably more complicated. Because these things are rather easily studied by accelerated aging tests, the formulation has improved since 1980s. It is likely true that modern triacetate film from Fujifilm and Kodak may be more durable, but I don't think it is correct to apply findings from modern material to early cellulose films. Old collections deserve more close attention in these areas. Another thing is that it is very misleading to describe one variable as "the most important factor" etc. here. For b&w silver image, humidity is an major factor, but even at 30-40% RH, if there is degrading paper or adhesive in the container, the image may degrade much faster. One must realize there are several ways to ruin an image just as easily and the image gets ruined from the weakest mode. It is often the case that the factors must be prioritized to fit in limited budget, etc., and humidity is one key factor that should be given a high priority, but a bit of peroxide from degrading paper or tape can do a big damage as well. It's not an "or" but rather an "and." In case of silver image, combination of proper sulfiding toner treatment can greatly reduce the impact of several variables and it is highly recommended for anything important. On Tue, 20 Mar 2007 12:05:36 -0400, "Gawain Weaver" <gawain.weaver@gmail.com> said: > Hi Richard-- > > 1) That's a good question. IPI did find that "paper envelopes offers no > advantage over plastic to control vinegar syndrome" (Environment and > Enclosures in Film Preservation, Bigourdan and Reilly, 1997). > > The question here is two-fold. First, does the plastic sleeve prevent the > acidic degradation products from diffusing away from the film? And > second, > if it does, does it matter? In other words, does the buildup of acid have > any effect on further degradation? > > In theory, since acetate base deterioration has been shown to be > acid-catalyzed and auto-catalytic, the buildup of acidic degradation > products will be harmful. However, in real life practice it is not the > determining factor in the life expectancy of film. > > > My SPECULATION on it goes something like this: There is no significantly > harmful acid-trapping effect from plastic sleeves on acetate film (di or > tri, they're both unstable) that is still in good condition and does not > have increased acidity levels. At this stage acid production is slow > enough > that acid diffusion away from the film is not a significant bottleneck. > > Degraded film with high acidity levels will undergo fairly rapid > acid-catalyzed hydrolysis regardless of whether the plastic sleeve > prevents > the acid from diffusing away from the film or not. IPI did find that > there > was a VERY SMALL advantage to be gained by the use of paper envelopes, > but > it is an insignificant factor if one is concerned with long-term > preservation. > > In the end, deteriorating film needs a cold and dry environment, ideally > very cold and moderately dry (say 0F, 25%RH) to essentially arrest > degradation. Short of such cold storage, any cooler storage with > moderately > low RH will be a vast improvement over room temperature. Attempts to > control > degradation by varying the type of enclosure have proven ineffective. > > 2) There is no specific risk to scanning, apart from the usual concerns > over > care and handling. I was simply warning against the casual use of > digitization for preservation purposes. > > 3) storage materials to avoid-- just the usual-- PVC, cellulose nitrate > or > acetate (that includes Kodak's triacetate sleeves), glassine, and poor > quality paper are generally to be avoided. Of course, the real > "acid-test" > in this case is the Photographic Activity Test, and many enclosures have > passed the PAT and are advertised as having done so. As Ryuji noted, > untoned > silver gelatin prints are susceptible to damage by many types of inferior > enclosures and other materials like adhesives. Certainly these things > should > be taken into account, and good quality enclosures should be used. > > The problem however, is that enclosures are a quick and easy fix, and > there > is a tendency to think that once everything is in a good enclosure that > the > collection is safe, and this couldn't be farther from the truth. Silver, > nitrate and acetate bases, and color dyes will degrade at room > temperature > and moderate RH and or in the presence of common pollutants like sulfur > dioxide, nitrogen oxides, and peroxides. They don't need poor quality > enclosures to degrade. And basements and attics with their extremes of > temperature and humidity will only make matters worse. I trust that Light > Impressions will convince people to use good quality enclosures, but > unfortunately that's not the most important factor by a long shot. > > Gawain > > -----Original Message----- > From: Richard Knoppow [mailto:dickburk@ix.netcom.com] > Sent: Tuesday, March 20, 2007 2:33 AM > > > Lots of snipping... > I have a couple of questions. > 1, I generally keep negatives in so called archival envelopes or sleeves, > is > there a problem with these when used for acetate film due to the surfaces > of > the film being pretty much sealed even though the ends are open? > > 2, By risk of digitizing for archival purposes do you mean that the > archival > storage of the original material may be ignored or is there a specific > risk > to scanning? > > 3, Are there storage materials you would specifically warn against? > > I always read everything you post> > > > > -- > Richard Knoppow > dickburk@ix.netcom.com > Los Angeles, CA, USA > > -- > > -- > No virus found in this outgoing message. > Checked by AVG Free Edition. > Version: 7.5.446 / Virus Database: 268.18.15/728 - Release Date: > 3/20/2007 > 8:07 AM > >
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