Caked on fixer stains

[DavidJRobertson]

I'm a little sloppier with cleanup than I should be so I have fixer stains all over the place. I've managed to clean most of the surfaces but annoyingly I can't shift a very visible ring (from the bottom of a bottle) on the bathroom countertop. It's absolutely caked on and I've tried everything I can think of to get it off with no luck.

What I've tried:

• Scraping it off
• 91% sulphuric acid drain cleaner
• Strong aqueous solution of potassium hydroxide
• Strong aqueous solution of sodium hydroxide and potassium permanganate.
• Sodium sulphite solution
• An aqueous acidified potassium dichromate solution
• A mixture of potassium dichromate and 91% sulphuric acid drain cleaner (no water added - extremely corrosive!)
• Following a Kodak guide which suggested treating the stain with hypochlorite bleach followed by fresh rapid fixer.

Any ideas?

 

[foc]

I would think that you could first gently scrape it off, using something like a flexible plastic spatula, so not to cause scrape marks. Then follow Kodak's suggestion.

 

[DavidJRobertson]

I tried scraping with a metal spatula and that didn't really do much. I didn't scrape too hard though to avoid scratching the surface.

 

[Rudeofus]

Fixer can deposit all kinds of stuff, maybe you could tell us which color that stain has?
Yellow: that's most likely Sulfur and will go away within a few hours or days with a mix of Potassium Hydroxide and Sodium Sulfite.
Brown/Black: that's most likely Silver Sulfide, in this case the Kodak method will likely work.

 

[RauschenOderKorn]

bathroom countertop

What is that counter-top made of that it will gladly accept a fixer stain but will let you treat it with 91% sulphuric acid for a prolonged period of time without any much worse effect?

 

[Svenedin]

In the UK we have various household surface cleaners that contain (dilute) household bleach along with detergents. One such product "Flash with Bleach" has removed fixer stains from my darkroom surfaces. It comes in a spray bottle for use in kitchens, bathrooms etc.

 

[Gerald C Koch]

If you can get it carbon disulfide will dissolve elemental sulfur. Be careful with it as it is very volatile and flammable.

 

[DavidJRobertson]

Fixer can deposit all kinds of stuff, maybe you could tell us which color that stain has?
Yellow: that's most likely Sulfur and will go away within a few hours or days with a mix of Potassium Hydroxide and Sodium Sulfite.
Brown/Black: that's most likely Silver Sulfide, in this case the Kodak method will likely work.

It's definitely not brown/black, i'd say it's sort of off-white/yellowish so sulphur is plausible. I'll give your suggestion a go, thanks.

What is that counter-top made of that it will gladly accept a fixer stain but will let you treat it with 91% sulphuric acid for a prolonged period of time without any much worse effect?

That fake reconstituted wood stuff with a tough plastic layer on top.

 

[DavidJRobertson]

Aqueous solution of sodium sulphite and sodium hydroxide hasn't touched it even after several hours.

Not sure where I'd get carbon disulphide, but I've ordered some xylene (well, mixed xylenes) since apparently sulphur is soluble in that.

 

[Rudeofus]

The reaction of Sulfur with Sodium Hydroxide/Sulfite may be much slower than your patience allowed for. I definitely do know that this mixture successfully cleaned out a bottle in which fixer precipitated a thick layer of Sulfur, but this may have taken a few days.

If you take a look at this patent, you can speed up the reaction with some tricks:

1. heat may be the easiest and most important. Process temperatures suggested in this patent are above 80°C, but even 60°C are better than room temperature.
   
2. the patent writes about cationic and anionic wetting agents, which you may find in dish washer or Photoflo/Ilfotol