So I started a Black and White Film photography class at my high-school (I'm a senior and this is the second time I've taken it). Today I was showing another student how to develop film (Kodak TMax400 in D76) and after we finished, the roll had a purple cast.
We asked my teacher about it and she said that we didn't fix long enough (We fixed for 18 minutes). She said that new Kodak Film was being made differently. She also said that we could remove the purple cast by letting the film dry overnight and fixing it again tomorrow.
Does what she is saying sound right? I am kind of nervous because I have a roll of Tri-X400 that I'm currently shooting and I don't want it to turn out purple. Any tips?
Over-fixed and insufficiently washed.
Film developing chemistry basics:
- It is best if *all* your B&W chemistry is done at the same temperature ... all development and fixing, all water washes should be at the same temperature ... unless you know precisely what you're doing and are 'bending' the process to achieve a given result. I prepare to process film by mixing the chemistry and filling my water supply jug the night before and letting everything stand on the counter overnight so that temperatures stabilize to room temperature. I set up the processing times by reading the time @ temperature development chart for the film type, exposure index used, and developer concentration. (I tweak that value per my agitation method and other experience.)
- Most standard solution developers are mixed to reuse for a number of films. If you process infrequently, you should mix developer concentrations for one-shot use, that way you always are ensured of fresh developer and consistent results.
- Using an acid stop bath is largely unnecessary. Most of what a stop bath is supposed to do is to keep fixer from being exhausted too quickly. I use a water bath instead, rinsing the film twice between developer and fixer.
- Fixer, like developer, is normally designed to be used for a number of films before it is exhausted. Over-fixing just embeds sodium thiosulfate into the emulsion which will eventually dissolve the silver grains and fade the negatives if not washed out. How long should you fix? Take an unexposed bit of film (say, the leader) and put it in a little puddle of fixer. Time how long it takes to become clear. That's the minimum ... add 50% to that and you have a good fix time. If it takes longer than 3-4 minutes to clear, either the fixer is too weak or it is almost exhausted: replace it with freshly mixed fixer.
- Washing should be long enough to expunge the residual fixer absorbed by the film emulsion, and not long enough to overly soften the emulsion. Ten complete changes of water is enough. I do it by filling the developing tank, agitating gently, stand for a minute, emptying, and re-filling rather than using a continuous wash so that I can maintain even temperatures. After the third rinse, I do a rinse with a hypo-clearing agent to chemically ensure that the fixer is removed from the film, and then continue rinsing for the remaining six fill and empty cycles.
- A quick bath in a wetting agent just prior to hanging the film to dry eliminates most water spots. I squeegee the excess water off the film by dipping my fingers into the wetting agent bath and running the film between my fingers.
Most film has a slightly blue to purple sheen until completely dry. Film that was insufficiently fixed tends to have a yellowish sheen over time as the residual fixer eats away at the silver in the emulsion.
G
