FP-100C Negative Cleaning Problem
Two months ago I began shooting FP-100C in a Zero Image 4x5 camera with a PA-145 film holder. This week I began to clean the negatives based on watching several youtube videos and reading comments on various websites. I had read that some people waited weeks or months to clean the negatives with no ill effects noted.
I cleaned a number of negatives. While the positives (prints) that I obtained in the field when I took the photos were good, most of the negatives had a reddish-pink color to them. When prints were made from scans of the negatives by a photo lab they had a green cast.
Before shooting the FP-100C film the film packs were kept in a refrigerator whenever one was available. When transported by car the film packs were in a makeshift camera bag on the floor where there was air conditioning. The camera bag was also shielded from direct sunlight by a sunshade. The ambient temperatures during shooting were typically 23 to 25 degrees Celsius.
After shooting the positives and negatives were placed in a cardboard drying box and fastened so that they could dry without anything touching the wet surfaces. The drying box was not designed to be light proof, but it had a top on it that was secured by a large rubber band. Direct sunlight could not enter the box.
The method for cleaning that I was using is a follows. I soaked each negative in water to soften up the paper around the edges of the negative. The paper was then removed. Water was put on a large glass plate and the negative was placed on the plate emulsion side down. The surface tension of the water held the negative to the plate and kept the Clorox from damaging the emulsion. The paper was removed from the edges of the negative to improve the seal with the water and the glass.
Clorox precision pour bleach gel was poured on the back of the negative and spread around with a small paint brush. The back of the negative was then rinsed. When all of the black backing was removed the negative was removed from the glass plate and rinsed again to remove the green gunk from the emulsion side.
It was after the negatives were hung to dry that the overall reddish-pink color of the negatives was noted. This color did not correspond to the colors on the prints obtained on the day of shooting.
First, I noted that after several cleanings that the bristles on the small paintbrush had disintegrated. I placed another brush from the same package in a pool of Clorox gel bleach on a glass plate. Within a minute the bleach pool turned a cloudy white and the bristles were disintegrating.
Second, I tried to rewash the negative to see if the reddish-pink color could be removed. It remained, but after the negative had spent some time in water the water (in a clear plastic bowl on top of a white sheet of paper) had a pink tint to it. After several hours there was no change in the color of the negative.
Third, I compared a normal FP-100C negative (so far I only have two normal ones) with one that had the reddish-pink color. Around the edges of the normal negative, where the paper had been, was the same reddish-pink color. However, it was confined to the edges and did not extend onto the image.
I changed the cleaning procedure. I did not removed the paper from the edges of the negatives, and taped the negatives to the glass plate with electrical tape. I poured Clorox gel onto the back of the negatives and did not use a brush.
The black backing was effectively removed as expected, but unfortunately most of the negatives I cleaned with this new procedure still had some of the reddish-pink color on them. However, the abnormal color did not extend across the entire image as with previous negatives. It was on only parts of the images.
I have read that other people have successfully used Clorox gel to clean FP-100C negatives. At this point I am beginning to suspect the gel. In spite of having read a lot of discussions about FP-100C negative cleaning and watching youtube videos, I have not been able to get any insight into this problem.
It appears that the reddish-pink color is the normal color of the negative without the emulsion on it. Any attempt to clean gunk off of the emulsion side, even by simply and gently placing the negative in a bowl of water, can result in losing emulsion and more appearance of the reddish-pink color of the negative material. Some posts on the internet lead one to believe that the FP-100C emulsion is fairly sturdy and can withstand slowly flowing water or a finger gently brushed across it. I don't think it is that sturdy. Best not to touch it with anything, including standing water.
I'd maybe give some other bleach a whirl. I just use the cheapest liquid bleach I can get, and glug it onto the negs. Not washing the negs beforehand I do think helps, however: the dried chemical goop gives a little protection to the emulsion from seeping bleach (or bleach that hits the neg when washing/removing from the glass or whatever), and I've had the emulsion get damaged when washing a second time around.
I just dug out a box of my 100c negs, and they do have a definite magenta tint to the emulsion in areas around the actual image, and green underneath where the paper was. The images themselves appear to maybe have some type of magenta tint. However, they scan up just fine on my Epson V600. Perhaps the lab performing the scan wasn't getting the color balance right? I've found this stuff can be a little different to scan. Do you have raw files for the scans?
Edit: Just saw your update about it. The emulsion is fairly durable when washing the dried up chemical goop off of it; soak it in water for a few min after bleaching, and running water will wash it right off, and the leftover paper stuff will peel off without taking the emulsion with it. If I remember, the goop turns a sort of whitish/milky color. The emulsion is far more vulnerable when re-washing, I've found.
I used to use Scrubbing Bubbles with Bleach, before it was pulled from the market. I'd be concerned if you're using full-strength bleach, as that might damage the negative at the same time it's removing the backing (viz the damage to your brush).