Stains on back of prints

Got a batch of prints that I did a few months back and half a dozen of them have brown stains on the back, varying from a couple of bubble sized dots to some goodly sized blobs. Done a lot of prints over the last five years but never had this before. The prints were, however, from some that I was doing as a bit of a batch job, three, four or five of each, expose, probably four (two pairs back to back) develop, back to back into the stop, bit of a wiggle to get some stop between the back of the sheets then back to back into the fix, another wiggle to get the fix inbetween them. Don't remember the wash sequence but it would have involved juggling the order of the prints.

Ilford FBIV, Mutligrade, stop, Hypam or rapid fix 1+4, one bath but never used for more than half its capacity.

I have to admit I always presumed that the fix primarily acted on the emulsion side but I presume that these stains are not enough fixing and I should just be more careful in future, more seperation in the fix when doing multiple prints. Or am I wrong and it's something else?

Hywel

It's poor fixing, it doesn't take much silver to cause these stains which is why 2 bath fixing is far safer, and also more economic.

Semi-soluble silver-thiosulphate complexes bind to the cellulose in the paper base, the second bath dissolves them fully.

Ian

Hi there Hywel. I agree with Ian. Think of fiber paper as a sponge: leave it in a bath of dissolved silver complexes, and they are going to get soaked up. Two-bath is about 4X as economical, and I think even more so if you hold your prints in a water bath after the first fix. I do my second bath at the end of the print session with the lights on, and never a problem.

Or, poor washing!

PE

Thanks, my suspicion, is that I've become a little lazy when it comes to the fixer when doing batches of prints; I've always thought of the fix being there to clear up the unused silver halide on the emulsion side. Never really thought about the back of paper soaking things up. Hence my laziness doing prints back to back and not being rigorous about separating them in the fix.

Then PE mentions my other concern; that it's a washing thing, as these prints would probably be from about the time I got my print washer. How would I tell the difference from the stain? (although as all the stains are on the back and all the prints go solo into the washer I'm still leaning towards the fix).

A well fixed print, by that I don't mean over fixed, but fixed in a final fixer bath with a very low silver content is less likely to stain if under-washed, rather the image itself will deteriorate over time due to the residual fixer breaking down into various sulphur compounds which will attack the silver in the emulsion layer.

Ian