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corrosive effects of darkroom chemicals?


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I just had a new sink installed in my darkroom and the stainless-steel basket strainer has rust beginnings. So far, to the best of my knowledge, I've only used plain water. But just to rule out all possibilities, suppose some dated D-76, Dektol, fixer, Photo-Flo was poured out. I don't use a stop bath. The sink itself is stainless steel and shows no corrosion.

 

Could these very standard chemicals cause rust?

www.paulwhitingphotography.com
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I just had a new sink installed in my darkroom and the stainless-steel basket strainer has rust beginnings. So far, to the best of my knowledge, I've only used plain water. But just to rule out all possibilities, suppose some dated D-76, Dektol, fixer, Photo-Flo was poured out. I don't use a stop bath. The sink itself is stainless steel and shows no corrosion.

 

Could these very standard chemicals cause rust?

 

Photo chemicals are corrosive however a good grade of stainless is immune. Stainless comes in many grades, photo grade is #316 most sinks #312 not as good. The strainer is likely not a good grade, Stainless is pacified during sink manufacture. It is treated with nitric acid. This cleanses the metal of any iron contamination from tools. Is low grade or traces of iron that you want to avoid. Never uses iron wool because if traces of iron imbed, they rust and this action causes the underlying stainless to corrode. Only nitric acid will stop this action. Under normal conditions, stainless corrodes but this is transparent and this coat protects the underlying stainless. Likely the sink will be OK for years and photo chemicals won't harm. The strainer is likely a low grade stainless or was never treated with nitric acid. I suggest replacing because it's corrasion may contaminate. Again, if corrasion starts, only nitric acid will stop and arrest. All photo chemicals are OK except Farmers Reducer which requires a sink made of red-brass (high copper content). .

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Here in Hawaii so called stainless steel will start to show "rust spots" within days of plain tap water hitting the material. The quality of stainless steel is smaller items like your debris basket is of question. I have knives, utensils and other kitchen items of SS that all show the "spots". I would not worry about the average volume of liquids you use. . just replace the basket now and then. Aloha, Bill
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I'm with Bill. Much stuff sold as 'stainless' these days is no such thing. And there are various grades of 'stainless' steel too. Some containing more chromium or nickel than others.

 

Good laboratory tools, like spatulas etc, are made of pure nickel and definitely won't rust. OTOH, I have a cheaply constructed Japanese made stainless steel developing tank that's showing a few rust blemishes!

 

BTW, some genuinely stainless items pick up low-grade steel from the stamping or bending tools used to form them. These specks get embedded in the surface of the stainless steel and will form rust spots quite readily.

Edited by rodeo_joe|1
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Most dangerous of all is the multi-strand 'stainless' cable sold cheaply in the big box hardware stores. A friend bought some and after cutting to length and swaging eyelets onto it left it outside for a couple of months. Corrosion was obvious and he returned it and managed to get a refund as it was not fit for purpose. Just as well he didn't use it on his boat in a salt water environment. We reckon that this steel cable is only plated but with what we don't know.
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Most dangerous of all is the multi-strand 'stainless' cable sold cheaply in the big box hardware stores. A friend bought some and after cutting to length and swaging eyelets onto it left it outside for a couple of months. Corrosion was obvious and he returned it and managed to get a refund as it was not fit for purpose. Just as well he didn't use it on his boat in a salt water environment. We reckon that this steel cable is only plated but with what we don't know.

If it's 'plated' it would be galvanised (tin plated) and would have a different look to stainless. Far more likely is that it's the low grade stainless being discussed here.

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If it's 'plated' it would be galvanised (tin plated) and would have a different look to stainless. Far more likely is that it's the low grade stainless being discussed here.

Galvanising involves zinc, not tin. This cable was sold as stainless steel but must have been a very poor grade. Troubling thing was it looked like any other multi core stainless cable. (I have been around sailing dinghys and boats for 40+ years and it would be very scary is someone used this for stays etc.)

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The hardest photographic chemical on metal is the bleach in color and reversal processing.

Very true.

Even 'good' stainless reels will get an etched appearance after being heavily used for colour processing. Having said that; the most consistent colour results are got from using a rotary processing machine that doesn't accept stainless reels.

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  • 3 weeks later...
Im using Xtol, Ilfostop, Ilford Rapid Fix, and Photoflo.

All developers have a reducing (anti-oxidant) effect. They'll actually have a preserving effect on metals, although they might leave a brown stain on crazed porcelain.

 

Used fixer shouldn't really be discharged into the drain, and doesn't need to be, since it's re-usable several times.

 

Stop bath and photoflo are used at such weak concentrations that they won't affect anything. Common vinegar is a stronger acid than stop bath working solution, and photoflo is just liquid soap.

 

In short, most household cleaning solutions are much more likely to remove the chrome plating from sink fittings. While plastic drain-pipe is made to withstand boiling water and all sorts of chemical attack. Don't worry, but flush your used developer away with running water to prevent it staining the porcelain.

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