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Pyro & selenium toning of negatives
I usually tone my negatives in dilute (1:30) KRST, but I've never done this
with my films developed in PMK. I can't think of any reason why I shouldn't, since I believe that the KRST has a positive ph & shouldn't detract from the stain. Any other opinions? -- -Lew The workers took the robot for Maria. |
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Pyro & selenium toning of negatives
"Lew" wrote in message news I usually tone my negatives in dilute (1:30) KRST, but I've never done this with my films developed in PMK. I can't think of any reason why I shouldn't, since I believe that the KRST has a positive ph & shouldn't detract from the stain. Any other opinions? -- -Lew Selenium or a sulfiding toner will tone the silver but not the stain. Actually, the stain image is a pigment and very permenant. Kodak Rapid Selenium Toner is probably about neutral pH, it is certainly not acid. Note that diluted KRST is no longer considered an adequate toner for preserving film. A better toner is Kodak Brown Toner. KBT tones all densities evenly so partial toning will provide protection to all parts of the image. KBT is quite alkaline. While KBT tones prints brown or sepia it may result in a slight cooling of image color of some negative emulsions. KBT or some other form of Polysulfide toner, is now the recommended method of protecting microfilm. -- --- Richard Knoppow Los Angeles, CA, USA |
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Pyro & selenium toning of negatives
Thanks, Richard:
Would you happen to know, or would you be able to point me to recommendations for KBT dilutions and times for this purpose? -Lew "Richard Knoppow" wrote in message nk.net... "Lew" wrote in message news I usually tone my negatives in dilute (1:30) KRST, but I've never done this with my films developed in PMK. I can't think of any reason why I shouldn't, since I believe that the KRST has a positive ph & shouldn't detract from the stain. Any other opinions? -- -Lew Selenium or a sulfiding toner will tone the silver but not the stain. Actually, the stain image is a pigment and very permenant. Kodak Rapid Selenium Toner is probably about neutral pH, it is certainly not acid. Note that diluted KRST is no longer considered an adequate toner for preserving film. A better toner is Kodak Brown Toner. KBT tones all densities evenly so partial toning will provide protection to all parts of the image. KBT is quite alkaline. While KBT tones prints brown or sepia it may result in a slight cooling of image color of some negative emulsions. KBT or some other form of Polysulfide toner, is now the recommended method of protecting microfilm. -- --- Richard Knoppow Los Angeles, CA, USA |
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Pyro & selenium toning of negatives
"Lew" wrote in message t... Thanks, Richard: Would you happen to know, or would you be able to point me to recommendations for KBT dilutions and times for this purpose? -Lew "Richard Knoppow" wrote in message nk.net... "Lew" wrote in message news I usually tone my negatives in dilute (1:30) KRST, but I've never done this with my films developed in PMK. I can't think of any reason why I shouldn't, since I believe that the KRST has a positive ph & shouldn't detract from the stain. Any other opinions? -- -Lew Selenium or a sulfiding toner will tone the silver but not the stain. Actually, the stain image is a pigment and very permenant. Kodak Rapid Selenium Toner is probably about neutral pH, it is certainly not acid. Note that diluted KRST is no longer considered an adequate toner for preserving film. A better toner is Kodak Brown Toner. KBT tones all densities evenly so partial toning will provide protection to all parts of the image. KBT is quite alkaline. While KBT tones prints brown or sepia it may result in a slight cooling of image color of some negative emulsions. KBT or some other form of Polysulfide toner, is now the recommended method of protecting microfilm. -- --- Richard Knoppow Los Angeles, CA, USA Not specifically for Pyro negatives. The recommendations for microfilm is to tone until there is a minimum of 60% conversion of the silver to silver sulfide as measured by bleaching out the silver and making comparision density measurements. One would have to do this once. However, I think that using normal dilution, 1:30, for perhaps 2 minutes would be right. There will be some visible difference from the toner. Even if its just visible the image will be protected. There is a great deal of information on protection of microfilm on the web. I would do a Google search to find sits. There is some information at the Conservation On Line site at http://palimpsest.stanford.edu but you should also check out the Image Permanence Institute which is operated by the Rochester Institute of Technology. It was an IPI investigation into degraded microfilm at the National Insitute for the Humanities that discovered the failure of diluted KRST to protect the film. KRST did work for many years but then stopped. No one knows the reason. Kodak swears that they did not change the formula. Evidently, something that was once in KRST caused some incidental sulfiding which boosted the protective effect, perhaps an impurity in one of the ingredients. Microfilm is more critical than pictorial film because it is much finer grain and, thus, more vulnerable to oxidation and unwanted sulfiding; loss of even a small area can be important because of the loss of data. Protective treatments for microfilm should ideally not change the structure of the silver image or change image color or density. All do to some extent by KBT and diluted KRST, when it worked, are satisfactory. Another toner used for microfilm is gold toner like Kodak GP-2. This is a very satisfactory toner but the gold content makes it expensive. -- --- Richard Knoppow Los Angeles, CA, USA |
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Pyro & selenium toning of negatives
"Lloyd Erlick" Lloyd at @the-wire. dot com wrote in message ... On Mon, 28 Aug 2006 21:04:33 GMT, "Richard Knoppow" wrote: There is some information at the Conservation On Line site at http://palimpsest.stanford.edu but you should also check out the Image Permanence Institute which is operated by the Rochester Institute of Technology. It was an IPI investigation into degraded microfilm at the National Insitute for the Humanities that discovered the failure of diluted KRST to protect the film. August 29, 2006, from Lloyd Erlick, Richard's post jogged the memory of the following post from Douglas Nishimura a few years ago: _______________________________________________ From Mon Sep 04 01:57:38 2000 Newsgroups: rec.photo.darkroom Subject: Warning: Negative base deterioration From: Douglas Nishimura Date: Mon, 04 Sep 2000 01:57:38 -0400 I was trying to think of a subject line that would catch peoples' attention. I hope it worked. If you haven't been using polyester based film (such as Kodak Estar base films), then I expect that most of you won't have any negatives left within a few decades. Let me give you the sad story first before I talk about the whys and hows. Long quote snipped... You can find a great deal about this by searching the web for _vinegar syndrome_. It is a serious problem for some "safety base" films both movie and still. Others have proven to be reasonably stable. As you know, the motion picture industry has had a severe problem with cellulose nitrate film base. All nitrate was discontinued in the US in 1951 (Sunset Blvd was the last picture on nitrate) but some of the safty base used after that has proven to be even less stable than the nitrate. Even though it does not pose the fire hazard of decomposing nitrate it still destroys the image. One difference is that old nitrate still film seems to hold up better than some 1950's acetate base. -- --- Richard Knoppow Los Angeles, CA, USA |
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Pyro & selenium toning of negatives
.... as in you just told *every*one else? Is there any hope besides digital?
What a nightmare. -Lew "Lloyd Erlick" Lloyd at @the-wire. dot com wrote in message ... On Mon, 28 Aug 2006 21:04:33 GMT, "Richard Knoppow" wrote: There is some information at the Conservation On Line site at http://palimpsest.stanford.edu but you should also check out the Image Permanence Institute which is operated by the Rochester Institute of Technology. It was an IPI investigation into degraded microfilm at the National Insitute for the Humanities that discovered the failure of diluted KRST to protect the film. August 29, 2006, from Lloyd Erlick, Richard's post jogged the memory of the following post from Douglas Nishimura a few years ago: _______________________________________________ From Mon Sep 04 01:57:38 2000 Newsgroups: rec.photo.darkroom Subject: Warning: Negative base deterioration From: Douglas Nishimura Date: Mon, 04 Sep 2000 01:57:38 -0400 I was trying to think of a subject line that would catch peoples' attention. I hope it worked. If you haven't been using polyester based film (such as Kodak Estar base films), then I expect that most of you won't have any negatives left within a few decades. Let me give you the sad story first before I talk about the whys and hows. I got a call around 1992 or so from Evelyn Hoffer (I hope that I spelled that right) a photographer in New York who was known for her coffee table books in the 1950s and 60s of European cities. She called because she went into her negative collection and found that they were all badly distorted and the emulsions were lifting off. We had been researching this problem since 1988 and were very aware of what the problem was. It was probably one of most difficult things that I've done -- to tell her that her life's work (other than what books and prints were already out in the world) was gone and there was nothing that could be done. A few could be saved by special methods, but it's so labor intensive that of her thousands of negatives, it would only be worth treating a couple. Think about it.....this was only 30 years or so......... Any film that you're shooting that isn't polyester (also called poly(ethylene terephthalate), trade names include Estar and Mylar) then you're on cellulose triacetate. All of the cellulose acetate film bases are made by taking cellulose (the main constituent of paper and trees) and modifying with acetic acid. (I'm oversimplifying here, but this is the general idea.) This is why it's cellulose acetate. Kodachrome film was on a variation of this base until about 1976 and then it switched to triacetate. Ektachrome sheet film was also on another variation, but all of these bases behave in the same way. The plastic base reacts with water and the humidity in the air is sufficient. The water in the presence of acids (and alkalines) pulls off the acetates as acetic acid (or vinegar) and you can smell it. Water alone can also do this, but the acid or alkaline acts as a special kind of accelerator called a catalyst. A catalyst makes reactions much faster without being consumed. (This is why the catalytic converter on your car only needs a tiny bit of platinum.) Consider then that one acid and water goes in and two acids (the original plus a vinegar) comes out. Those two can go into a reaction to produce four acids and so on and so on. This is what we call an autocatalytic reaction...The stuff is generating it's own accelerator to destruction. If we measure the deterioration over time, it starts out very slowly and slowly gets faster. Eventually it generates enough acids that it reaches what we call the "autocatalytic point" and the reaction really accelerates and gets faster and faster. To visualize what I see when we measure acidity over time, take a piece of paper and draw an x and y axis. Now draw a line that starts just above the x axis and rises at maybe a 10 degree angle. At the end of this line draw a line that is almost at 90 degrees. Round the sharp angle where the two lines meet. This is more or less how the reaction goes. Right at the elbow is what we call the auto-catalytic point. Now...at the same time, acids and water can also react along the length of the long plastic molecules causing them to break into shorter pieces. This reaction is acid (or alkaline) catalysed, but is not autocatalytic. Removal of the large acetate groups as acetic acid vapors causes the film base to shrink. It will ultimately shrink about 10% to 15%. At the same time, the gelatin emulsion is trying to stay attached, but it's not shrinking so eventually the adhesion between the base and the emulsion gives out and we see this as "channelling." You literally find tunnels formed by the emulsion (on top) and the separated base on the bottom often about 1/8 inch in diameter. Sheet films with an anti-curl layer will also do that on the anti-curl layer side as well. Breaking of the plastic molecules into short pieces meanwhile causes the base to get brittle. I've shocked my students by giving them a sheet of deteriorated film and letting them flex it. It eventually has the flexibility of fresh potato chip. I've crumbled a negative between my fingers like crisp bacon. Meanwhile plasticizers in the base become incompatible and they start coming out as perhaps feathery crystals or as oily liquid filled blisters, or as solid plugs. The feathery crystals are about the most common plasticizer, tri-phenyl phosphate. The oily liquid plasticizer is a phthalate, often dimethoxyethylphthalate. How fast can this happen? If you stored your negatives constantly at a comfortable 70F (21C)/50% relative humidity, we would expect to see fresh acetate film hit the autocatalytic point in about 40 years. In the case that I mentioned above, every summer she would close-up her Manhattan apartment and head to Europe so the negatives literally baked in the humid New York City heat which greatly reduced the life of her negatives. To give you an idea about how fast this thing can go, let me give you an example. Suppose that we track the acidity in the base over time. It starts out very very close to zero and at the auto-catalytic point has x amount of acid. Now I mentioned that at 70F (21C)/50% RH it will take about 40 years to create x amount of acid. How long do you think it would take, if we left it stored under the same conditions, to double in acidity or to reach 2x acidity? Let me tell you that it will be about another 5 years....and to increase to 3x acidity would take around another 2 years. Most of you don't have 70F/50% RH storage. Temperature and humidity play a big role. If you were at 75F (24C)/50% RH rather than 40 years, it would take roughly 25 years to reach the autocatalytic point and another 4 years or so to double. Humidity also plays a big role (since the reactions need water.) If you were at 70F/80% RH not only would I worry about mold, but you'll reach the autocatalytic point in about 17 years. However, if you were in a very dry place at say 20% RH, it could take about 90 years to reach the autocatalytic point. I should add that the autocatalytic point isn't the end of life for your negative. It'll stink, but will still be printable. Even at double the acidity, you should still be able to use the film, but time left is very short. Now before people start calling the manufacturers to complain, it isn't their fault. In the early 20 th century when acetate bases came out to replace nitrate, they ran accelerated studies and found that the acetate hardly deteriorated at all while the nitrate was falling apart like crazy so they thought that it was pretty darn stable. Unfortunately they didn't realize that the reaction needed moisture and they were running dry oven tests. (The RH was probably only around 5% to 8%.) They started getting complaints in the 1950s or 60s, but they were all from tropical countries (parts of India, south-east Asia, South America,....) and they thought that it would only happen in tropical countries. Much to their surprise it started showing-up in north america starting in the early 1980s. People said that the triphenyl phosphate also reacts with humidity to form phenol (aka "carbolic acid") and phosphoric acid. This was true, but even film that contained different plasticizers also deteriorated. Some people said that it was the nitrate subbing layer. [Gelatin didn't stick very well to cellulose acetate, but it did to cellulose nitrate and cellulose nitrate also stuck very well to cellulose acetate so they used a very thin layer of cellulose nitrate as a glue to stick the emulsion to acetate bases up until at least the early 90s or so.) Well, research showed that it wasn't the nitrate subbing either because film with and without the subbing layer deteriorated at about the same rate. (More recently companies have found how to make gelatin stick and the nitrate subbing layer isn't used anymore.) Some people worried that it was processing since people were using acid fixing baths and acid stop baths. Well, it's not the processing either. I have a large box of unprocessed sheet film that just stinks. About the only thing that you can do is to store your negative at a reasonably cool temperature. In fact the ISO and ANSI standards recommend that collections store their acetate negatives below 45F (and only then if they can be stored between 20% and 30% RH otherwise they have to be even colder.) One of the lessons that we've learned about this is that bad conditions count for more than good conditions so even if your place is pretty good most of the year, but bad during the summer, the summer will kill you. Consider my apartment. I keep it pretty cool during the winter (I like the cold) and it sits at 55F and a humidifier keeps it around 50% RH. If my apartment was like that all the time, my negatives wouldn't reach the ACP for about 100 years. During the summer though its often 85 or worse since I don't have a good flow of air through the place (due to window locations.) The humidity also gets pretty high (although my bedroom is air conditioned.) At 85F/70% RH I should reach the ACP in about 9 years. What are the comparable effects of these two extremes? We'll ignore the spring and fall and for simplicity say that my apartment is at each condition roughly half the time (all other times are somewhere in between.) The overall effect is that my negatives (if I stored them there) would reach the ACP in 16 or 17 years. They would be toast in less than 25 years. Now most people don't keep their places as cold as I do in the winter and most people in Rochester would find even less time before they were in trouble. This is not to say that every negative stored under these conditions will suffer this fate. We find it to be like people. You find the odd 90-year old who still smokes a pack a day. Who knows why they're still around? We also find the odd negative that does better or worse that we would expect. However, anecdotal evidence from collections suggest that on average, our estimates are pretty good. We run a seminar every August and back in the early 1990s I asked how many people (there were usually around 50 participants) had acetate deterioration in their collections and a few people put up their hands. Each year the number of hands increased and now there's virtually no one who says no (unless they don't have any acetate negatives.) The motion picture industry spent millions on cold storage in the past 10 years just because of this problem. They call it "vinegar syndrome" for good reasons. People there ask how much vinegar can come out of film so I ran a calculation based on typical triacetate film -- 1000 ft of 35 mm. This is roughly equivalent to 200 rolls of 36-exposure 35 mm film or roughly 200 8 X 10 sheets. Ask yourself how much vinegar you might expect if we took all of the acetate off of the film and turned it into aqueous vinegar (as you buy it in the store.) The amount is just a tiny bit less than one US gallon. You can smell acetic acid at very low levels by the way-- roughly 1 ppm in the air. Polyester will more or less do the same thing (producing ethylene glycol (anti-freeze) and terephthalic acid.) However if it takes say 100 years for acetate to reach some point of deterioration at 70F/50% RH, under the same conditions, it would take polyester somewhere between 500 and 10,000 years to reach the same state. This is why we don't tend to worry about it with polyester. You may ask why the companies don't switch totally to polyester. They're certainly trying to, but it's not necessarily all that easy. One problem that needs to be dealt with is know as core-set. (This is different from a corset. :^)) If you roll plastic film tightly onto a small reel....like a 35 mm spool...you cause stress. The outside of each lap of film is larger than the inside of the lap. (We see this at the Olympic field events. The runner in the inside lane has a shorter distance to run so must start further back to compensate.) Inside the plastic these stresses cause the polymer (plastic) molecules to slide against each other to relieve the stress. This is known as "cold flow." The plastic is literally changing shape at room temperature. The result is curly film. I remember when I was in high school standing in the dark with this roll of incredibly curly film trying to get it onto a film real. Ack. Cellulose acetate takes on core-set faster than polyester. However, what happens to the curly roll after processing? It hangs nice and flat (pretty much) certainly nothing like the horrible mess you were trying to get onto the reel. This is because acetate film absorbs a fair amount of water during processing (a few percent by weight) and this causes the core-set to be released. Polyester, on the other hand, only absorbs a fraction of a percent water by weight during processing so 35 mm polyester film would come out of processing about a curly as it went in. Imagine how hard it would be to print curly negatives. As far as I know, the only 35 mm polyester film on the market right now is Techical Pan. The industry is working on the problem though and may even now have a solution. (And they may be producing much more 35 mm polyester film.) Polyester, as I've mentioned in regard to photo enclosures, is also fairly expensive and tends to dull cutting blades pretty easily. By the way, you may hear of people saying that this base deterioration is just a "diacetate problem." It's not true. When diacetate film was made starting in the late teens they didn't add as much plasticizer and one of the consequences was a larger degree of solvent pooling. Have any of you ever tried to dry tomatoes? If you don't cut them up, the outside dries quickly forming a hard shell outside. Water from the inside can't pentrate this hard shell so the tomato stays wet inside and eventually rots. Acetate film base has the same problem. It's cast by mixing the plastic with methylene chloride (and a few other solvents) to form a viscous syrup called "dope." This is poured onto a very large, continuously rotating wheel. As the wheel turns, heaters and fans (effectively) evaporate off the solvents so that by the time the wheel has made one rotation, the film base can be peeled off for coating. The solvents evaporate off the surface very quickly but this forms a solid outside while there's still solvents trapped inside that can't get out. One of the things that the plasticizer does is to reduce the amount of trapped solvent. (It's primarily added as a fire retardant.) By the time you get the film, it contains around 2% solvent by weight and this slowly evaporates out over time. (Causing the film to slowly shrink very slightly.) When they made diacetate, they didn't include as much plasticizer so the there was a greater amount of solvent loss shrinkage and since acetate deterioration also manifests itself as a shrinkage, people assumed that they were the same problem. (Diacetate will also get acetate deterioration, but the initial rapid shrinkage found with diacetate was solvent loss and not base deterioration.) On a historical note, nitrate film was the first cellulose based film to be case on a wheel. Prior to that they used a glass table at Kodak that was made from a single piece of perfect glass 200 feet long and 40 inches wide. The glass had to be absolutely flat with no scratches. In the afternoon they poured the nitrate dope onto the table and then they turned on big fans and opened all the windows. (Obviously there was no EPA then.) In the morning, they closed everything up and poured on the emulsion (in the dark.) When the emulsion had set, they peeled the film and cut it up then poured the next batch of base. Now as bad as this sounds, prior to this, they used to shave sheet film base off a block of cellulose nitrate. One last thing.... polyester doesn't suffer from solvent loss shrinkage because it has to be melt cast rather than solvent cast. The melt is extruded into a sheet and then undergoes several physical modifications. One thing that they do is known as biaxial orientation. They take the extruded film and they heat it up and pull it in the length direction they repeat the process in the width direction as well. I never can remember the order and it may be width first. What this does is causes the plastic molecules to line-up in the plane of the film. (If this was a bed full of kids, all of them are lying down in different directions, but no one is standing up.) The last thing they do is to add dimensional stability by partly crystalizing the plastic. (For the chemists out there, of course that can't be done, but parts of the molecule end-up in a closest packing state.) If this wasn't done, if the film was heated (say in a projector), the base would shrink. Anyway, I'm hoping that if I can spread the word through the world of photographers I won't have to tell anyone else that there's nothing left of their life's work. -Doug Douglas Nishimura Research Scientist Image Permanence Institute |
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Pyro & selenium toning of negatives
"Lew" wrote in message t... ... as in you just told *every*one else? Is there any hope besides digital? What a nightmare. -Lew "Lloyd Erlick" Lloyd at @the-wire. dot com wrote in message ... On Mon, 28 Aug 2006 21:04:33 GMT, "Richard Knoppow" wrote: There is some information at the Conservation On Line site at http://palimpsest.stanford.edu but you should also check out the Image Permanence Institute which is operated Lots of snipping.... Unfortunately, digital storage methods are not yet archival and have a rather poor track record. If one is able to transfer data from one medium to another at fairly frequent intervals the life can be extended, but that is a real problem when one considers the enormous amount of material that is archived these days. Also, while digital records, in pricipal, can be transferred many times without loss of data, there is a limit beyond which there is some, or even total, loss. Phototraphic materials have a much better track record. The particular support material that is subject to "vinegar syndrome" was widely used for film for at one period and for a fairly long time, but other types of cellulose acetate are not affected by it and are surviving. Even some nitrate base has proven to have a relatively long lifetime. Paper is extremely long lived when stored under even reasonably good conditions; many people have family photographs which are approaching a century in age and have survived despite the lack of archival storage methods. Eventually we well have digital storage methods capable of centurys of life, but they are not available yet. -- --- Richard Knoppow Los Angeles, CA, USA |
#9
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Pyro & selenium toning of negatives
there is a limit beyond which there is some, or even total, loss.
Please explain. I see no reason why the chain of copying the most recent copy should ever end, even using today's materials. -Lew |
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Pyro & selenium toning of negatives
On Wed, 30 Aug 2006 20:13:34 GMT, "Richard
Knoppow" wrote: many people have family photographs which are approaching a century in age and have survived despite the lack of archival storage methods. August 31, 2006, from Lloyd Erlick, You know, this is exactly what made me a photographer. Or maybe it's more accurate to say it made me a portraitist. Bits of paper with mysterious images of people (my 'relatives'??) — stored carelessly. I doubt that digital files, stored well or poorly, would have affected me. regards, --le ________________________________ Lloyd Erlick Portraits, Toronto. website: www.heylloyd.com telephone: 416-686-0326 email: ________________________________ -- |
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