Mineral stain on print

I get this "stain" on prints after selenium toning, and using a home brew hypo clear.





It looks sort of like fingerprints, but it's not. It doesn't come off with PEC-12, which makes short work of grease like fingerprints. I toned 44 prints yesterday, and 12 of them had those marks. The good news is, it does come off in a short (10 second) rinse in fresh stop bath. I could do without the extra steps though, so I'd like to get to the bottom of this issue.

I absolutely never see these stains on an untoned print. I also absolutely never see them unless I hypo clear. So it's related to one of these.

I re-use my selenium for years, keeping a gallon jug topped up and filtering it every now and again. I don't have any recollection of having this issue with a fresh batch of toner, as that's a pretty infrequent event.

My hypo clear is a 2% solution of sodium sulfite in water with a pinch of EDTA. Yesterday's mix was 40g sodium sulfite, and 0.5g EDTA in 2000ml water. I hypo clear the prints after selenium toning for 3 minutes. Prints are rinsed prior to hypo clearing.

I add the EDTA in an effort to reduce this sort of mineral staining. It's not working so hot! Maybe I'm adding too much, or too little? Yesterday, I noticed that the hypo clear was a bit "cloudy" at the end of the session.

Any problem solvers out there who can help me with this?

Thanks!

It's the Toronto water, Bob Carnie was getting something similar using Sodium Slphite as a wash aid it's a good idea to do the final rinse in de-ionised or distilled water. I just used a water jug type filter here in the UK where my water is very hard and comes frome a borehole, I have worse issue when in Turkey as our borehole is close to the sea, I would get similar on films if I didn't use bottled water for the final rinses.

Acetic acid (stopbath) should dissolve the deposits.

Ian

I'm no longer in Toronto, but probably have similar tap water. So you're suggesting after the hypo clear I give a rinse in distilled water? Or are you saying after the final wash?

I was under the - possibly mistaken - assumption that the EDTA took care of this sort of thing.

Ian, if it is the water, how then do you explain the artefact being random spots?

The fact that the spots come off in an acid environment (stop bath) would suggest that they are calcium carbonate or other similar "hard" water deposits that acid can dissolve.

My suggestions:

First, squeegee your prints well before drying (I use a dedicated windshield wiper blade) and dry them face-up to avoid contamination. Getting rid of the excess water and any droplets will likely solve the problem.

If that doesn't work, use a distilled-water final soak after the wash and before squeegeeing to leach out the minerals. Three to five minutes would be my starting point.

You might also try a weak stop bath mixed with distilled water before the wash (and after the hypo-clear) and see if that does the job.

Hope this helps,

Doremus

Hello Doremus, thank you for the suggestions - I always appreciate your input. You always have a good way of thinking these issues through.

I think I do a pretty good job of squeegeeing my prints prior to them going on the racks - I have a good rubber squeegee. There's certainly no pooling water on either side of the prints. I'll pay more attention the next time round though - so many of these tasks you just end up doing by rote.

I'll also try a distilled water soak, but my question regarding that is: if I only have this problem post selenium / hypo clearing, why isn't it occurring for the rest of my untoned prints? My washing / squeegee process is otherwise the same.

The weak stop suggestion is also interesting, and I'd sooner do things that way as opposed to having to rewash prints after discovering the problem. I wonder about staining, what with left over selenium and the acid stop bath. I guess I can run a few tests.

Marco

AgX said:

Ian, if it is the water, how then do you explain the artefact being random spots?

Click to expand...

It's just odd patchesthat dry last, can be quite random.

Ian

Yes, if it is a deposit occurring at drying. But when I asked that still was not clear to me, but I rather had the idea that it was about some interacting during development.

Marco,

If there's a deposit on your prints after drying, something, from somewhere, was in the last water the print spent time in and is left behind when the water evaporates.

So, if it's something from the selenium toner, then it's not washing out. Same with the wash aid. Maybe extending the wash time will help. If it's something insoluble from wherever, then you need to track down which solution is contributing the contaminant. You may need to replace things in your regime one-at-a-time till you find the culprit. Maybe something's too old?

If it's the wash water itself, then the distilled-water final bath would definitely help.

The weak acid bath is a possible remedy for prints with deposits on them, to dissolve them away if they can be.

Best,

Doremus

When I lived on the US Gulf Coast, I never had drying marks.Then I moved to the desert in Arizona, and that's when I got drying marks on both film and prints. Using distilled water for everything did nothing. Then I read of someone who spritzed their fiber prints w/ distilled water after hanging them on the line. So I did that, along w/ running the shower beforehand and letting the bathroom get really steamy.

That not only eliminated the drying marks on my film and prints, it also allows me to hang the fb papers by a single corner like an rc print. They dry w/ a natural curl and are only minimal wavy on the very edges. After I set them under some weight for a few days they were perfectly flat.

momus said:

Using distilled water for everything did nothing.

Click to expand...

Did you use destilled water for washing?
If not, the paper after washing was saturated with your hard water. And maybe even a short dip into a wetting bath would not cure that. But then the effect of that flushing on the line surprises me.

If you used destilled water even for the washing, I would be even more puzzled.

Can someone make me wiser on what happened here?

AgX makes a good point: if you want to get hard-water minerals out of the paper, you need to soak it a while in distilled water. I'd go for 5 minutes for starters. And refresh the distilled water bath often.

That said, I've never had problems with tap water and papers. I've had film develop deposits before, though, and the distilled water bath does the job just fine. With papers, a good squeegeeing has always worked for me. (I love that word, "squeegeeing" )

Best,

Doremus

A quick follow up to this thread:

I found a hypo clear formula posted by Wolfgang Moersh, and have been using it for the past month or so, and have seen none of the staining I was experiencing in the original post.

For 1000ml water
20g sodium sulfite
1.2g EDTA
0.6g sodium bisulfite
0.4g sodium citrate

In the same darkroom environment, using the same replenished selenium toner, on the same paper, using this hypo clear eliminated the problem. My guess is that simply adding more EDTA was the answer.