Roman chemistry: pickling baths

[richsc]

Since in the Roman bronze/brass I've seen there isn't a hint of firescale or other tarnishing, did they have the chemical equivalent of pickling solution (not the cucumber stuff)? I was thinking in terms of field demos at Roman Days, but if I'm going to anneal my bronze in a forge, I surely want to clean it off quickly. How did they do it? Firescale is most unpleasant to look at.

Brings me to the 2nd point: if they did have it, and knew how iron stuck in a pickling bath took on some copper, did that make for a kind of rust protection done deliberately?

[Marcus Mummius]

Since in the Roman bronze/brass I've seen there isn't a hint of firescale or other tarnishing, did they have the chemical equivalent of pickling solution (not the cucumber stuff)? I was thinking in terms of field demos at Roman Days, but if I'm going to anneal my bronze in a forge, I surely want to clean it off quickly. How did they do it? Firescale is most unpleasant to look at.

Brings me to the 2nd point: if they did have it, and knew how iron stuck in a pickling bath took on some copper, did that make for a kind of rust protection done deliberately?

I guess the just used vinegar after anealing. Posca would work too

I always use vinegar after annealing a cupric alloy and it works great.

Vale,

[Matt Lukes]

Same here. Vinegar works wonderfully even in a very low concentration. I've tried even about 2% (regular table vinegar is 5% acetic acid by volume) and it does the job- it's a little slower than full-strength, but it's not a huge amount of time really.

[Gaius Julius Caesar]

So is there a problem with full strength?

[M. Demetrius]

Well, yes, "full" strength would dissolve copper right away, and probably produce toxic fumes, like any other concentrated acid. The hotter concentration that can be bought at hardware stores is around 15% (for prepping galvanized metal for painting, usually, and killing cactus), and as already said, regular grocery store vinegar is 5%.

You don't want lab grade acetic acid around. Risky biz.

[Titus Petronicus Graccus]

A period solution is to use urine.
However, given the amazing stink that you get from doing that (trust me...) I would not advise it.
Stick to vinegar, far safer.

[richsc]

I will have to see if the chemists have to say: since today's pickle, sodium bisulfate, holds copper in solution and coats iron with it, does vinegar do the same thing? Not so you might notice it but enough to protect from rust?

[Gaius Julius Caesar]

Sorry, I was meaning full strength vinegar, my apologies.

[M. Demetrius]

Sorry, I was meaning full strength vinegar, my apologies

None needed. I was just being wooden-headedly literal. :?

Now where's those cucumbers? You did what? You put them in laboratory grade acetic acid?? That explains the jar of green slime by the sink. :lol: :roll:

[Gaius Julius Caesar]

A period solution is to use urine.
However, given the amazing stink that you get from doing that (trust me...) I would not advise it.
Stick to vinegar, far safer.

Hey, somebody had to try it! :wink:

[Matt Lukes]

I will have to see if the chemists have to say: since today's pickle, sodium bisulfate, holds copper in solution and coats iron with it, does vinegar do the same thing? Not so you might notice it but enough to protect from rust?

Yes it does- you end up with copper acetate, and it does redeposit copper on steel I found

[M. Demetrius]

Do you need to run DC current through it? I remember plating with copper sulfate in school, but I don't remember which lead to fasten to which metal. Been a while.

[Matt Lukes]

Nope- it's a very light deposition, just kind of gives the steel a copper hue. I suspect that if you did run current through, you would get real plating, but just conatct is enough it seems.

[Robbie Phillips]

I have used vinegar and salt to clean copper and brass. As a kid, my parents would have me clean the the copper-bottom cooking pots or pans from the kitchen. We'd get the metal wet with vinegar and scrub it shiny with a small brush and salt and rinse with soapy water. I've cleaned old brass sheet metal and belt buckles this way too. Hope this helps with your question-