cleaning brass - chemistry

Where's your spirit of adventure? There's unlikely to be enough for a large bang regardless though on your own head (or more likely eybrows) be it.

However,

Regardless, I am not a chemist but IIRC metal+acid can produce hydrogen but metal and base doesn't and sodium carbonate (washing soda) / sodium bicarbonate (baking soda) are bases.

Alternatively, rub with lemonjuice and salt or vinegar, salt and flour to remove the tarnish.

WP

I had consderable success over the weekend dunking some tired brass parts in brick acid (HCl) - which left a reddish deposit on them which came of easily with a brush or pan scourer.

I might give that a go then, I was a bit concerned about acids (particularly strong ones) leaving the brass pitted.

In message , WhingingPom

I wasn't really worried about a bang as the windows were open as a precaution, however it was fizzing away pretty vigorously and I'd have had trouble putting the flame out were it flammable.

Tried various stuff, but it's a very thick patina.

Cover in HP sauce, wait a few hours wait and then use a toothbrush in the crevices.

Adam

Cheap soy sauce works well, too.

Sheila

Neither willl work very well. Ammonia in particular is likely to cause more trouble than it solves, particularly for discolouring it (although it might fake up some patina for you, should you want it)..

Best cleaner for brass is simply vinegar and scrubbing. For door knockers, a fibre glass brush (pen shaped) is good.

I wouldn't use salt and vinegar (or HP sauce or soy sauce) on brass or especially on bronze. It's a powerful cleaner, but it can be hard to completely remove the chlorides afterwards and you can get pale green crystals of coper chloride appearing long after.

Well don't leave it there forever...and weash off later.

I was too, but tried on a little bit first, and it came up good so I did the lot..

In message , ARWadsworth writes

I tried Sainsbury's tomato sauce, but it had no discernible effect.

Now soaking in (diluted) brick cleaner . . . anyone know what typical %HCl brick cleaner is? (Jewson's in this case)

Possibly the worst cleaner for bronze you could possibly use - not quite as bad for brass, but still not a good idea. Watch out for green crystals appearing in the future.

In message , Andy Dingley writes

Thanks, I'm now the proud owner of a splendid gleaming brass door knocker. The final recipe for success was an overnight soak in warm citric acid {something like 8 heaped table spoons in two pints of water), this left a thin reddy black film that further soaking wouldn't shift, which was removed with a brass wire brush (I prefer these to the fibre glass ones as they don't leave fibres stuck in your fingers)

The citric acid soak may have been a little too much (or it may have been the earlier aluminium foil and washing soda treatment) as in places the brass has a coppery tint where, I guess, the zinc's been preferentially etched.

Thanks to all for the advice.

That's why you wash it off afterwards...

What you get is cuprous Chloride initially - sort of loose red rust. That comes off readily.

No doubt it would turn to cupric chloride eventually, but is that green? I thought that was copper carbonate and copper sulphate (blue)

Copper chloride is black isn't it?

Tomato sauce is used to polish off fish and chips not brass

Adam

The problem is that this is _very_ difficult to achieve reliably. You need to use benzotriazole to neutralise it properly.

Go and look up "bronze disease"

Mm. Bu we aren't burying these brass or bronze artefacts for a thousand years Andy. Just cleaning up a doorknob that is going to be grasped by hands every day, which will wear it all away anyway.

I got the impression from (skim) reading the article that the problem was caused by the chorine salts remaining on the bronze and, in particular storage conditions, acting similarly to a catalyst, it did sound fairly dramatic having artefacts reduced to a pile of dust.

I was thinking the rain would wash it off, but I guess there could be some chlorine salts on the back, I suspect once the frosty season starts it's going to be exposed to chlorine salts anyway.

the danger is not so much leaving it pitted as leaving it pink - if you let the acid take out too much zinc leaving just the copper behind. Vinegar diluted in water is good, remove when the pinkness just starts to appear.

if the brass has previously been laquered you'll need to remove that first with paint stripper.