Pickling solution?

[Bo’sunParticipant @bosun58570]

Good afternoon,

A while ago I made up some pickling solution from CuP Alloys “cleansing salts” and all worked fine.  Having saved the solution for future use, I find the plastic container it’s in has what looks like mould growing on the sides and lots of black bits floating around.

Is this normal?  Is the solution still usable, or should I start again?

I believe the salts are citric acid based.

[Bill PhinnParticipant @billphinn90025]

It sounds like it’s outlived its shelf life.

I usually use sodium bisulphate for pickle, or white vinegar if I’ve got none of the former mixed and only need a small quantity.

[Harry WilkesParticipant @harrywilkes58467]

Ive had the same thing happen with some old citric acid in the first instance I used it then threw it out for the record it did work OK

H

[SillyOldDufferModerator @sillyoldduffer]

Yes, normal.

Citric, Acetic, and Formic Acids are all weak organic acids, and some bacteria and moulds eat them.   (So do people in that many fruits contain Citric Acid, and Acetic Acid, aka Vinegar, is a condiment.)  They’re bio-degradable and gradually go-off.  However, a bit of mould on top wouldn’t stop me using older acid as a workshop pickle.  Change it when it stops working, smells, or the biology escapes from the bucket.

Sulphuric, Nitric, and Hydrochloric are all strong inorganic acids, pretty much deadly to all forms of life.  They don’t go-off and are powerfully quick, which is a good thing industrially.  Apart from Hydrochloric, they require special handling and licences, so probably more trouble than they are worth in a small workshop.  Hydrochloric isn’t recommended as a pickle because it tends to leave Chloride ions behind, which can cause corrosion underneath paint and plating later.

Sodium Bisulphate is a good compromise: “Sulphuric Acid half neutralised”.   Inorganic, doesn’t go-off, cause severe burns, need a licence, or more than sensible handling precautions.   The original Harpic Toilet Powder found in every home was Sodium Bisulphate but the modern stuff isn’t, I think because accidentally mixing toilet Bisulphate with toilet bleach emits Chlorine gas , which is nasty.

Dave

[FulmenParticipant @fulmen]

IIRC you can get sodium bisulphate as pH Down (pool supplies).

[JAParticipant @ja]

I believe CuP Alloys cleaning salts are citric acid (as it says on the packet) and a biocide. I kept aquious solutions of the salts in glass jars (away from sun light) for years and never seen anything growing.

I would not throw it away without straining out the growing matter first and then trying it. If it does not work then it is hardly likely to damage any metal.

JA

[bernard towersParticipant @bernardtowers37738]

Like JA my Cup salts are very old and in a glass jar and have no growth. They are used regularly.

[Bo’sunParticipant @bosun58570]

Hi All,

Many thanks for the replies.  After an hour in the solution, nothing noticeable happened, so a new mix is on the cards.  While the cost is fairly minimal, I just abhor wasting stuff.

[Martin KyteParticipant @martinkyte99762]

Curious as to why JA keeps his pickle away from sunlight?

regards Martin

[Grindstone CowboyParticipant @grindstonecowboy]

Late to the conversation, but I suspect it may be down to the plastic container – I’ve found on numerous occasions that black “mould” will grow in liquids stored in plastic, where glass does not have the same problem. Might be due to tiny scratches harbouring microbes, or something to do with the chemical make-up of the plastic?

Try glass jars.

And another thought, once you’ve pickled some copper parts, would the copper tend to have a biocidal effect?

Rob

[Grindstone Cowboy]

On Grindstone Cowboy Said:

Late to the conversation, but I suspect it may be down to the plastic container – I’ve found on numerous occasions that black “mould” will grow in liquids stored in plastic, where glass does not have the same problem. Might be due to tiny scratches harbouring microbes, or something to do with the chemical make-up of the plastic?

Try glass jars.

And another thought, once you’ve pickled some copper parts, would the copper tend to have a biocidal effect?

Rob

From my experience,  no, it does not.

James

[Martin Kyte]

On Martin Kyte Said:

Curious as to why JA keeps his pickle away from sunlight?

regards Martin

Only because it is on a shelf away from the window. Sunlight does encourage the growth of things.

I should add, after using the pickling solution I pour it back into its jar to re-use. The solution eventually gets a bluey-green tint, I guess from copper, tin and silver citrates. These three metals are powerful biocides.

JA

[Martin KyteParticipant @martinkyte99762]

Sunlight certainly helps anything that photosynthesises but for bacterial growth the UV should help keep the pickle clean. UV lamps are routinely used as pond cleansers and as a general thing UV is quite damaging to cells.

regards Martin

[Bo’sunParticipant @bosun58570]

I would have stored it in a glass jar, but two litres is too much for any glass jars I have.  Just wish I still had the half gallon demijohn I threw out a few years back.

[File HandleParticipant @filehandle]

There are microbes that live quite happily in boiling sulphuric acid. The organic and inorganic chemically means the presence or absence of carbon, and bears no relation to their use by living organisms. having said that citrate is an intermediate in the citric acid cycle involved in the metabolism of many living organisms.

[Martin KyteParticipant @martinkyte99762]

Interestingly Haemocyanin is the oxygen carrier in the blood of some invertebrates notably octopus and horseshoe crabs where the element that binds the Oxygen is Copper rather than Iron. OK maybe you won’t get bothered with an octopus in your pickle but it illustrates that pretty much any element gets employed by life in some form or other. In fact Copper is quite important in human health.
(I know I’m off topic again)

regards Martin

 

 

 

[Fowlers FuryParticipant @fowlersfury]

Re: Cu ions, metallic copper and biocidal properties.
Years ago the marked biocidal properties of copper and its alloys were observed and described as “oligodynamic properties”.  The value of brass door handles came to the fore again at the beginning of the Covid epidemic in reducing the spread of infection, whereas modern, more common, aluminium & plastic handles were considered to lead to spread of the virus.

A reputable source of opinion and research is Harvard and a relatively recent review is:-
https://harvardtechnologyreview.com/2020/10/30/harnessing-the-oligodynamic-properties-of-copper-to-reduce-disease-transmission-during-a-pandemic/

I think that black particles in a strong mineral acid, used pickle (HCl or sulphuric) are insoluble oxides or flux residues.
(Shorter wavelength UV (e.g. UV-B & UV-C) light does not pass through normal bottle or window glass, only UV-A).

 

[File HandleParticipant @filehandle]

Not sure who wrote the article, but I don’t believe that finely divided copper forms a solution in alcohol.

Not from this article but elsewhere “Metals which exhibit the oligodynamic effect include mercury, silver, copper, brass, bronze, tin, iron, lead and bismuth.
Of all metals, the strongest effect is exerted by mercury and silver.”
our fridge has silver in it for its biocidal properties, so this is not a new idea. And Bordeaux and Burgundy mixtures have been used for some time in horticulture, both based upon copper salts.

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