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From: (Don Wilkins)
Newsgroups: rec.crafts.metalworking
Subject: Re: Help needed cleaning copper
Date: Mon, 14 Jul 1997 03:20:15 GMT

On 13 Jul 1997 18:42:34 GMT, "Bill Cottrell" <>

>I am using a mini oxy. - acet. torch to melt shapes out of .006 copper
>sheeting. I need (preferably an easy way) to clean this copper back to
>bright appearance so I can go into the finish process (making colors run
>using controlled heat) and then coating with polyurethane. I have ready
>access to sulfuric and nitric acids for baths if someone knows how to use
>these with copper cleaning. Thanks for any help.

Take a shot at muriatic acid (about 20% hydrochloric acid) which
should be available from most hardware type stores. It will clean the
oxides off and not attack the copper as long as you don't leave it in
the solution for extended periods of time. Full strength will work but
more dilute will be cheaper.

Hydrochloric acid is an excellent solvent for the copper oxides but
will not dissolve significant amounts of copper unless there is an
oxidizing agent present. Dissolved oxygen (from air) will serve as
that oxidizing agent hence the caveat about "extended period of time".

Sulfuric acid will work but may put holes in your underwear (or worse)
if you are not careful and nitric acid will dissolve copper metal and
skin if too strong. Hydrochloric may sting a little but it will remind
you to head for the water rinse with no permanent damage.

Try to keep the stuff off of the skin and out of the eyes.

  _               _   _                  Für d' Flöh gibts a Pulver
 (_|   |   |_/o  | | | |  o              für d' Schuah gibts a Wix,
   |   |   |     | | | |      _  _    ,   für'n Durst gibts a Wasser
   |   |   |  |  |/  |/_) |  / |/ |  / \_  bloss fuer d' Dummheit gibts nix.
    \_/ \_/   |_/|__/| \_/|_/  |  |_/ \/

Subject: Re: Cleaning Oxidized Copper?
From: (Don Wilkins) 
Date: Aug 08 1995
Newsgroups: rec.crafts.brewing (Jeffrey Ziehler) wrote:

>Don Wilkins ( wrote:
>: I didn't get the original either.
>: Try muriatic acid (hydrochloric acid). Dilute it  about 5 H2O to 1
>: HCl. It will dissolve copper oxide but not copper metal.  I presume

>just remember that when diluting acids, it's acid into water, not water 
>into acid.  Adding water to acid could generate too much heat and cause 
>problems.  Adding the acid to water, one can wait for it to cool down, 
>then add more acid, wait...etc.

>safety first.

Not true. You get the same amount of heat generated no matter which
way you mix them. It is a good rule to remember but in this case the
problem doesn't exist at all.
The problem you are referring to is with concentrated sulfuric acid.
The problem is two fold (1) the difference in specific gravities and
(2) the amount of heat generated. 
When you pour water into concentrated sulfuric acid it flows over the
surface and does not mix well. There is tremendous heat generated and
in fact can cause dangerous splattering.
When you pour the  concentrated sulfuric acid into the water (because
of its high specific gravity) it flows under the water to the bottom
of the container and the result is some substantial mixing which
alleviates the problem.
Now after some 50+ years as a research chemist I do it a little
differently. First of all if I was mixing H2SO4 & H2O I put the water
on a stirrer and poured the acid in quickly. Don't mess around putting
in a little and waiting. But an even better way is to weigh out he
appropriate amount of ice in a beaker and add the H2SO4. Smooth as
silk and you have already dissipated  a large amount of the heat.
This is probably more chemistry than any one in this group wanted to
know. Muriatic acid is available from local hardware stores or farm
product sources. It is cheap and not difficult to work with. Be sure
to rinse the pipes because I can guarantee that you won't like your
brew with a little shot of HCl.

Not mentioned and probably should have been. WEAR SAFETY GLASSES.
It will make the skin sting a little after it has been on for a short
time but if you get it in your eyes it will be extremely painful and
could cause serious damage. It is a chemical and should be treated as

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