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Saturday, September 8, 2012

Favored Method For Antiquing Brass

I have never really liked brass very much because it doesn't react well to liver of sulphur.  Instead of producing an antiqued patina, it just looks dirty.  It would be easy enough to purchase a professional patina fluid (Jax, Sculpt Nouveau, Birchwood Casey, etc.) but I like to use the most natural methods whenever possible.  I've struggled to get a finish that I actually like because I don't like shiny brass.  I moved to satin finish and then to hammered so that I could break up the light and reduce the shine but I quickly tired of hammered both.  Green and blue patinas were easy to produce by using Jax Green, vinegar, salt, and ammonia.  But I have definitely found my favorite method.

I read about a method used to antique recesses and details in gold (gold doesn't react to liver of sulphur) jewelry which entails plating the item with copper.  That is the same method that I use to copper plate silver solder seams.  I wrap 0000 steel wool around a toothpick and dip it into old (blue-green) pickle and rub it over the solder seam.  The reaction between the steel and the pickle causes a chemical reaction that plates the copper molecules in the pickle onto the solder seams.  In the example of gold jewelry, the entire item is plated leaving a thin coating of copper.  The copper layer is easily removed from the high points by using 3M Polishing Papers, etc. and the copper remains in the recesses and will darken when the item is treated with liver of sulphur.

That gave me the idea to make use of the copper gilding that occurs naturally when brass is annealed.  Brass is an alloy of copper and zinc with zinc being the more volatile or unstable of the two metals.  When brass is exposed to the torch flame, the uppermost layers of the metal are oxidized but the zinc reacts more readily leaving behind less of the zinc and a pink gilding of copper.

I first need the thin layer of copper.  Fold formed or hammered pieces have already been annealed, zinc depleted, and are copper gilded.  After the item has been pickled to remove firescale, the pink layer of copper is revealed.  For etched brass, I like to plate the piece using the blue-green pickle and 0000 steel wool method. 

Peachy-Pink Cu Layer on Fold Formed Brass
Peachy-Pink Layer of Copper on Fold Formed, Annealed Brass

Those who wish to return the item to the original, raw brass appearance, usually remove this by using a special pickle made with a 1:1 mixture of  pickle (I use vinegar & pickling salt) and hydrogen peroxide.  Not removing this layer or copper gild gives me a surface that will react with liver of sulphur to produce antiquing.  I then hand polish the piece with 3M Polishing Papers to remove the copper from all the high points leaving the copper in only the recesses. 

Disc Polished With 3M Polishing Papers
Disc Polished With 3M Polishing Papers

After that, I tumble polish the item as usual.

Tumble Polished Disc & Domes
Tumble Polished

The item is then treated with liver of sulphur in the same manner that I would treat a piece that is solid copper.  The copper gild that remains will react with liver of sulphur to accentuate the metal's detail and pattern while the raw brass portions react minimally.

Disc & Domes Treated With Liver of Sulphur
Treated With Liver of Sulphur


After a hand polishing with a Pro Pad or 3M Polishing Papers and a few rubs with a Sunshine cloth, the item is finished.

I can feel good about using this method and recommending it to others because it is an inexpensive, environmentally friendly method of antiquing brass.
If you try this method or have already been using it, I'd love to see the results!  Please feel free to leave your Flickr or other photo-sharing links in comments.

9-10-12 Edit:
 Brass Was Plated With Copper, Tumble Polished, & Treated With Liver of Sulphur (Not Yet Hand Polished)

L:  LOS-Treated Copper Plated Brass (Polished) R:  Polished LOS-Treated Copper

6 comments:

  1. This is a really cool technique, thank you so much for sharing! Trying it in the near future :)

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    1. You're very welcome. I like to use the least amount of chemicals so, this method really appealed to me. Plus, I'm cheap ;)

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  2. Thanks so much for sharing this info. And your earrings are gorgeous!

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    1. You're welcome, Cynthia and thank you so much for the compliment! :)

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  3. All that work makes it not all that "inexpensive"! But I like your results. The fold-formed discs and the earrings do have a very pretty finish. I kind of like what just plain ammonia does to my red brass (from Monsterslayer); the finish isn't as dirty-greenish as the one from LOS.

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    1. Thanks so much!

      For me, it's not any different than the amount of work that I'd do using any other finish. It's just polishing. That's the beauty of using what's already there. Rather than using the pickle/hydrogen peroxide mixture and removing the copper layer from the brass and then using a patina liquid to give it color, I just polish it down until copper remains in the recesses and treat it with LOS. The pieces that aren't annealed and need to be plated only take a minute or two to plate and then it's the same drill! It's actually pretty fast.

      I wish that I could get ammonia to just darken brass but with our heat & humidity around here, it starts to turn blue--no salt needed!

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