How do you remove silver nitrate stains?

[robshepherd]

It was only going to be a matter of time after switching to Kallitype printing...

Do any of you know how to remove silver nitrate stains from a porcelain sink?

Thank you!

[goamules]

Try hypo fixer.

[Bob Salomon]

In the USAF we used to process 20x20” prints in trays in a large sink. 4 of us standing at the sink. One with the dev. tray, one with a water bath, one with fixer and one with wash. This was a resin based DuPont paper in the early 60s and we would do this for hours at a time. If you had the developer tray you ended up with mahogany colored nails! At the end of the shift you would stick your hands in the fixer tray for a couple of minutes and that would clear the stain.

[Two23]

Several things to try. Make a paste of Comet cleanser and press that on the stain, then put a damp folded paper towel over it. Leave overnight. Straight fixer can work but take many applications spread over a number of days. Hydrogen peroxide and ammonia 50/50 with repeated applications sometimes works. And sometimes, nothing works at all. If you live in Europe you can find some Silvosol that's supposed to be good.


Kent in SD

[Gary Beasley]

There was a product called developer system cleaner that was basically dichromate bleach. Stands to reason if you have any C41 bleach handy you can try that then scrub it with fixer and rinse.

[Doremus Scudder]

Assuming the stain is mostly metallic silver, you can rehalogenate and then use fixer to make it soluble in water.

A solution of chlorine bleach should turn silver into silver chloride. After the stain is gone, use fresh fixer to dissolve the now invisible stain away. If you omit the latter step, the stain will gradually reappear.

Doremus

[Duolab123]

I worked in a analytical lab summers and vacations as a kid. We would mix 1 molar silver nitrate 2 liters at a time. 340 grams of silver nitrate in a 2L volumetric flask. I don't remember exactly who or what happened, but the flask broke. Someone grabbed a mop and a bucket, we mopped everything up, dried the floor with paper towels, no one hurt, no big deal. Came back the next day, floor was black! Well more like a deep chocolate brown. Fortunately the vinyl floor had about 20 layers of floor wax. There was a couple of us peons who got down and using razor blades we scraped the entire floor.

I remember we would buy silver nitrate, Eastman Chemical brand, 1lb brown glass bottles, 20 plus bottles at a time, reagent grade, $80 a pound.

[robshepherd]

Thank you all for the ideas!

Duolab123, interesting summer job. How was all that silver nitrate being used?

Doremus, I tried your idea first since I have bleach on hand. The sink has been full of bleach water for almost 3 hours now, and the stains are slowly disappearing. Will use some fresh fix on it maybe later this evening.

Kent, I did read about Silvosol. It's supposed to work well. But you're right, I couldn't find a source here in the states.

Thank you everybody! I appreciate the ideas. -Rob

[robshepherd]

Hypo did not work. Bleach however took care of it after an overnight soak.

[Gary Beasley]

Did you use the hypo before or after the bleach? The bleach can leave a residue that will darken again, the hypo should get rid of that after you bleach. If you remember, C41 process has bleach then fix or both mixed as blix to remove the silver.

[Doremus Scudder]

Hypo did not work. Bleach however took care of it after an overnight soak.

As mentioned, you should use fixer to remove the now-invisible stain after bleaching or it will come back.

Best,

Doremus

[Two23]

Now that we have a thread started and the OP answered, I'll add a little. Last month I was removing my trays etc. from the portable dark lab in the back of my Subaru after shooting wet plate. I had one of the trays full of water and a lot had sloshed out into the plastic storage box I used as the base of my dark lab. I was tired and thought, "Just water." I dumped it out on the ground. A few days passed but then one morning I looked and there was a big brown spot! The previous days had been heavy overcast but now it was sunny. Uh oh, wife isn't going to be happy. So I've washed it with a power washer, poured hypo on it and let it sit and then washed again, tried 50/50 ammonia and hydrogen peroxide. All of that lightened it but it's still there. It has a bit of a silvery sheen to it now. Should I try chlorine bleach, wash, and then high strength hypo again? My thinking is it's down into the pores of the concrete. Might get rid of some of it with a wire brush.


Kent in SD

[koraks]

It's likely the most valuable concrete slab out there, it being silver plated and all. I'd leave it as it is.

[robshepherd]

Doremus, I did just that. Look ma, no more stain! Thanks, Rob