Quote Originally Posted by Photo Engineer View Post

If on the positive, you see a reddish yellow image, this means that those dyes are becoming absent in the original. These are affected by heat and humidity and the magenta, in particular, is affected by the lack of stabilizer.

Thank you for the info P.E., at least I know what's going on. I'll bear it in mind when deciding how to store the collection, though I'm not sure i want to start soaking 40 year old negatives in anything. :-)