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Fine Embellishment Everything from hand engraving and scrimshaw to filework and carving. The fine art end of the knifemaker's craft.

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Old 12-10-2012, 12:54 PM
Imakethings Imakethings is offline
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Location: Boone, NC USA
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Patinas for Copper, Brass, and Bronze

Eli gets the blame for making me think of starting this thread, he asked about patinas for brass, so I set out to do a few using only the stuff/chemicals I have floating around my home and shop. While I do have some slightly exotic stuff I'm going to try to produce most of these results with stuff I think is fairly common.

I'll be updating this post with pictures as I run through different patinas and I'll provide a list of ingredients I used to get a specific result and on what. If you have any specific requests for a patina feel free and I'll see what I can puzzle out.

Blue/purple/violet on brass or copper.
Required chemicals: Ammonia, common table salt (sodium chloride).

Procedure:
Get an airtight container that you can fit your piece to be treated in. Fill the bottom of it with a small amount of ammonia (windex, simple green, and several other ammonia based all purpose cleaners also work quite well). Spray the piece with a salt solution or sprinkle salt on to it. If you spray it you'll get a much more even coating, if you sprinkle you'll get a much greater amount of variation on the piece.
Let it sit for awhile, check it after about an hour to see how things are progressing, you should start to see discoloration on the surface of copper at this point, and probably not much of anything if you're looking at brass.
Check back in on it every couple hours till you get the coloration you want, seal with whatever type of goo you prefer.

Update with pictures:




Next up/pending: Rokushō

Last edited by Imakethings; 12-10-2012 at 07:52 PM.
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Old 12-10-2012, 09:30 PM
Imakethings Imakethings is offline
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The intended recipe for the Rokushō patina:

15g copper acetate
15g copper sulfate
0.5L solution of white vinegar diluted 5-12% with water

How I'm making the ingredients:

Copper acetate can be made by mixing equal parts hydrogen peroxide and distilled white vinegar, boil it for a moment or two then let it cool down a bit, I'm letting mine simmer on low. Throw in some copper, doesn't matter what, just so long as it's copper and reasonably pure, wire, tubing, sheet, whatever, doesn't need a whole lot 20-30g will do fine. Let it simmer and react, you'll get bubbles and it will slowly turn a blue green color. Keep it on low and it will slowly evaporate leaving you nice copper acetate crystals.

Copper sulfate is much easier to make. Most of your big box home improvement stores will carry copper sulfate as a root killer for septic systems, read the ingredients and you should be able to find it without too much problem.
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Old 12-10-2012, 10:23 PM
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Eli Jensen Eli Jensen is offline
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Thats two threads now I'm blamed for. Great info I'll have to go over it in more detail later
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Old 12-10-2012, 10:33 PM
Imakethings Imakethings is offline
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Well as you can see the brass did fair to middling, I'm thinking I'm going to try a different method for applying the salt to it and see if I can get it to have a more even patina.

Current attempt for the ammonia-salt solution:
I lightly oxidized the surface of the brass with peroxide and then brushed on a solution of salt and water, allowed to dry, and put in the closed container with ammonia. Keep in mind, the brass is not sitting in the ammonia, it's just in the same closed container with the ammonia and not touching it.

Update: lightly oxidizing the surface was a bad idea, it didn't produce the coloration I wanted, just kinda a muddy brown. So I've scratched it and reset using just a salt solution on the surface and reapplying to get uniform coverage.

Update II: Much better results for the finish, a great deal more uniform, but not blue enough.

Last edited by Imakethings; 12-11-2012 at 02:33 AM.
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Old 12-11-2012, 12:27 AM
Imakethings Imakethings is offline
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In other news the above Rokusho patina presented the following results after lightly sanding and a mild acid dip in HCl. I boiled it in the solution for about 15 min.

Brass gave me this:


And copper did this:


Not bad for a red, but I think I can tweak it to get a brighter red.
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Old 12-13-2012, 03:44 PM
Imakethings Imakethings is offline
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Unless someone comes up with another color for me to try and puzzle out this endeavor is going to die.
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