[Prev][Next][Index][Thread]

copper clean-up?



----------
From:  RWB355-at-aol-dot-com [SMTP:RWB355-at-aol-dot-com]
Sent:  Saturday, August 22, 1998 12:41 PM
To:  tesla-at-pupman-dot-com
Subject:  Re: copper clean-up?

Hi Dan, all


My answer to your prob depends on a few things:

1.) Is the green stuff really patina? i.e: copper carbonate
2.) Or is it copper acetate?.
You can tell the difference because #2 (copper acetate) really eats away at
 the metal.

If it is just patina (CuCO3) AND (!!) the sheets are pure copper, there are
 several different ways to do it. All methods will remover copper to some
 extend, but there is no other way.

1.)
Mix some acetic acid (not vinegar, its too diluted) and a few tablespoons of
 table salt. This mixture makes a very dilute solution of hydrochloric acid
 (HCL) and is not very dangerous to use. Rub this solution on your copper plate
 (or dip it) with a cloth.
Rinse with clean water afterwards.

2.) 
A stronger (faster and deeper working) solution can be made of 1:2 conc
 sulfuric acid and destilled water. (be sure to pour the acid into the water
 NOT the other way round) Use as above, except you need gloves. To neutrilize
 the acid mix up some sodium hydroxide (lye) with water. A solution of 1:100 is
 good enough. Add the lye slowly to the water, as this is also an exothermal
 process (generates heat). Donīt leave the solution on the copper too long as
 it will turn your fresh copper into CuOH. Rinse with water.

3.) You can use some scouring agent like powdered soap or AJAX and rub the
 copper plate with it and a SOS pad and water. This method is the least
 dangerous. Needs a lot of elbow grease, tho.

4.) Take 25% ammonia (you can add a shot of lye and about 30% Canada Dry Club
 Soda (mineral water) which speeds up the process a bit) and rub the copper
 with it. It will turn to blue copper hydroxide, which can be removed with
 hydrochloric acid rather easily. This is really hard on copper, so use it only
 if the stains are deep. Shooters use this method to clean their barrels after
 shooting large quantities of copper-cased bullets.

5.) If you want a polished surface (none of the above give you this): You can
 hit the sheets with fine steel wool followed by 400, 600, 800 and 1200 grit
 wet and dry sandpaper. This will give you a mirror smooth surface. It will
 tarnish rather quickly, however, so you will have to coat with clear coat. Of
 course you can only do this on pieces (or places) where you donīt need to make
 an electrical connection.

I use the above methods to restore old tube radios. But be sure it is pure
 copper. If its just plated all of the above methods will remove the (thin)
 plating.

hope it helps,
Reinhard