Whats the chemical for "chemically blackening"?

[Guest]

I've come across about 2 dozen references to chemically blackening brass parts, including this instruction book in front of me, but none of them say exactly what the chemical is.  So...whats the secret sauce?

 

B

[xken]

Try this product from JAX Chenicals. I have used this in the past and it works great but follow the instructions.

 

https://www.jaxchemical.com/jaxshop/shopexd.asp?id=61

Edited July 22, 2016 by xken

[Cathead]

I posted a short forum a while back about a similar product from BlueJacket, it has some responses, advice, and my own followup experience with the product.

 

http://modelshipworld.com/index.php/topic/12757-experience-with-bluejacket-metal-toners/

[Guest]

Thanks guys.  Any idea what the "active ingredient" is in these products?

[grsjax]

Phosphoric acid is a common one.  Probably other chemicals as well.

[xken]

30. Black (For Cast Bronze and Brass) Ingredients  

• Sodium Thiosulfate... 6.25 gm [MORE INFO]
• Ferric Nitrate... 50 gm [MORE INFO]
• Distilled Water... 1 L

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 July 22, 2016 by xken

[dgbot]

MetalBlackeningnew.pdf

Here is a PDF that should give you all the info you need.

David B

 

[dvm27]

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?

[Gaetan Bordeleau]

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 July 23, 2016 by Gaetan Bordeleau