cleaning damaged slides : LUSENET : B&W Photo - Film & Processing : One Thread

This is one for the books. My cat urinated on a number of slides. I've considered everything from dishwashing liquid,to Photo-Flo,to lye soap, but I've held off pending wiser counsel. Any solutions? Please, no pee jokes. I've heard enough.

-- donald owen (, November 29, 2000


I've never had that problem, but what I would try if they were my negatives is to take the least important negative, and try immersing it in an acetic acid bath. The reason I suggest this is that cat urine is a very strong base, and the acetic acid should neutralize it.

It might stain the negative, as when you mix an acid and a base, you get salt and water (if I remember my chemical theory). A thorough wash and immerion in a wetting agent, such as Kodak Photo-Flo, would be desirable before drying.

I recall reading in a newspaper column advice for a person who had the problem of cats spraying on the siding on his house; it was suggested that he try a 40% solution of acetic acid (2 parts glacial acetic acid to 3 parts water) to neutralize the odor. The stop bath suggested for general photographic use is a solution of about 1.3%, which probably have little or no effect on the cat urine; I would hazard a guess that a 28% solution would be the best place to start. If it doesn't work, try a more concentrated solution. Be sure to take all the usual precautions, such as eye and hand protection when handling acid, and don't forget to add the acid TO the water, not the other way around!

Let me know how you make out.

-- Terrence Brennan (, November 29, 2000.

I should have read your posting more carefully; you did say SLIDES! Try my suggestion on your least important SLIDE; I'm not sure what effect acetic acid of 28% will have on the dyes.

-- Terrence Brennan (, November 29, 2000.

I would guess that most of the minerals and proteins are water soluble anyway as the cat uses water to wash them out of its body. So maybe you should try water (maybe with a wetting agent in the last bath) first.

-- Thomas Wollstein (, November 30, 2000.

Donald: I don't know if using acetic acid will solve your problem or not, but I do know that you should not use glacial acetic acid (or anything nearly that concentrated). It is not necessary, and is much more likely to harm the slides than duilute acetic acid. (I don't like to tout degrees, but I do have a PhD in Chemistry.) Urine contains ammonia, other amines, minerals, salts, etc. All of which are water soluble. The overall pH of cat urine is basic, but is not characterized as strongly basic. I would suggest soaking a test slide in a large amount of water (preferrably distilled, can buy in supermarket); I would also use warm water, since the E6 process is run at 100.4 degrees. This should bring most if not all the urine residue into the water solution. Then I would change the water and resoak in a dilute sloution of acetic acid (as a guess, even more dilute than stop bath, and probably at room temperature). Let the slide soak for a few minutes, and then rinse in clean warm water. As an aside...There are many reasons why you don't want to or need a concentrated acetic acid solution: (1) it is corrosive, and may destroy the dyes; (2) based on numbers, you don't need it. There is plenty of acid present in dilute acetic acid to neutralize the amines in the quantity of urine present; (3) as part of the acid + base = salt and water reaction, heat is formed as a byproduct. Using a concentrated acid, will result in a very loacalized generation of heat (probably right on the film surface), which could be enough to damage the emulsion. In a dilute solution, the water acts to "buffer" the heat, and prevent any localized heating. Good luck and hope this helps. Arnie

-- Arnie Milowsky (, November 30, 2000.

One major problem with all the above advice. The color dyes are stabilized from fading with a formaldehyde solution, somewhere in the development process. If you just wash the slides in water (which is how I would start), the dyes will rapidly fade over time.

You need to re stabilize them. The Kodak process took the formaldehyde out of the final rinse years ago, the final rinse is similar to PhotoFlo with an activator for previously introduced less hazardous formaldehyde compounds early in the process. The other processes (Jobo/Tetnal, Beseler, Unicolor, etc) still have a formaldehyde based final rinse/stabilizer step. Some of thoese sell that step separately from the whole kit. You should use this as the final step in recovering the slides.

And of course, start by removing them from the mounts. While they are wet, watch that they don't stick together.

Overall, I would remove them from the mounts, wash them in distilled water, with several changes of water, then stabilize them, then remount when dry. If you wash with water, you really don't need an acetic acid step, but if you want to do that, it probably wouldn't hurt. I would use 1/2 strength stop bath, and NOT indicator stop (could add the indicator color to the slides).

-- Terry Carraway (, November 30, 2000.

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