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Whats the chemical for "chemically blackening"?


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30. Black (For Cast Bronze and Brass) Ingredients  

Process  

Heat immersion - 1 minute.

When article is immersed in hot solution (120-140°F, 50-60°C) a succession of colors is produced. It changes to a purplish color after about 45 seconds. The color darkens quickly and the article is removed after about 1 minute. Wash thoroughly in hot water and air dry, wax finish.

 

Here is a link to the rest of the formulae:

http://www.sciencecompany.com/Patina-Formulas-for-Brass-Bronze-and-Copper.aspx#30

Edited by xken
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The best blackening agent I ever used was ferric chloride and ammonia, based on a technique described in Model Shipwright. It was a very nasty concoction, however, and extreme caution was used while preparing and using it. I have had mixed success with Jax products and also very good success with automotive spray paint primer and matte or flat black finishes.

 

Ken - your formula is for cast brass but I assume it works for other brass as well?

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I used to mix some solution. I do not exactly remember the recipe but it came from jewelry.

there was ammonia about 30% and copper nitrate powder and water to adjust the %.

 

You do not want to smell ammonia because it can put you down very fast!!!

Edited by Gaetan Bordeleau
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