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Brass photo-etchs treatment for blackening

I keep my procedure simple. A jar with 100% ammonia. A small , round, plastic shelf to place the items. They are only exposed to the ammonia fumes. The pics show some cannon barrels in the jar and one after treatment. They come out a bit more like a dark, bronze colour. I like it. I have also tried this with rings/hooks but you have to be careful how long they are in the jar, as they can become brittle and break. A few hours maybe. Good luck.P1070047.JPGP1070048.JPG
 
Th
frankieg said:
I keep my procedure simple. A jar with 100% ammonia. A small , round, plastic shelf to place the items. They are only exposed to the ammonia fumes. The pics show some cannon barrels in the jar and one after treatment. They come out a bit more like a dark, bronze colour. I like it. I have also tried this with rings/hooks but you have to be careful how long they are in the jar, as they can become brittle and break. A few hours maybe. Good luck.View attachment 173696View attachment 173697
Click to expand...

Nice, thank you for showing us your method.

How do you do the blackening to photoetched parts ?

In the same way?

Thanks
Daniel
 
Brass is an alloy.... Modern brass is about 70% copper and 30% zinc with some additional elements added sometimes for different applications. Ammonia WILL color brass, HOWEVER... please remember what frankieg said about cracking.!!!
Ammonia attacks the zinc in the alloy. The result is a form of stress corrosion cracking. The more zinc there is in the brass, the worse the cracking. In modern brass this IS a problem. Once the zinc percentage in the alloy rises above 15% the problem gets worse. Since modern brass is about 30% zinc....well, you can see what’s going to happen.

Obviously, the thicker, heavier brass in a cannon is not as critical as thinner pieces. Thinner pieces, like photo-etched, WILL BE affected, and you won’t like the results.!!
Brass, contains stress risers wherever it has been cold formed. Any brass piece that has been formed, shaped, bent, etc. will have these stress points. These stress risers become focal points for stress corrosion cracking. Exposing these brass components to ammonia will cause them to crack. It might happen immediately, OR it might happen weeks or months later.
It doesn’t have to be a lot of ammonia either.!! I have seen (yes, ME..!) brass ammunition start cracking around the shoulder and neck of the cartridge case after being stored in a dry shed with bags of fertilizer. The ammonium nitrate in the fertilizer was enough to affect the brass cases. I didn’t think about it at the time. I should have stored it in hermetically sealed containers instead of wooden packing crates.!! Lesson learned.!!!!

Bottom line = Keep ammonia away from modern brass alloys...ESPECIALLY thin sections.!!
 
Hobbit99 said:
Brass is an alloy.... Modern brass is about 70% copper and 30% zinc with some additional elements added sometimes for different applications. Ammonia WILL color brass, HOWEVER... please remember what frankieg said about cracking.!!!
Ammonia attacks the zinc in the alloy. The result is a form of stress corrosion cracking. The more zinc there is in the brass, the worse the cracking. In modern brass this IS a problem. Once the zinc percentage in the alloy rises above 15% the problem gets worse. Since modern brass is about 30% zinc....well, you can see what’s going to happen.

Obviously, the thicker, heavier brass in a cannon is not as critical as thinner pieces. Thinner pieces, like photo-etched, WILL BE affected, and you won’t like the results.!!
Brass, contains stress risers wherever it has been cold formed. Any brass piece that has been formed, shaped, bent, etc. will have these stress points. These stress risers become focal points for stress corrosion cracking. Exposing these brass components to ammonia will cause them to crack. It might happen immediately, OR it might happen weeks or months later.
It doesn’t have to be a lot of ammonia either.!! I have seen (yes, ME..!) brass ammunition start cracking around the shoulder and neck of the cartridge case after being stored in a dry shed with bags of fertilizer. The ammonium nitrate in the fertilizer was enough to affect the brass cases. I didn’t think about it at the time. I should have stored it in hermetically sealed containers instead of wooden packing crates.!! Lesson learned.!!!!

Bottom line = Keep ammonia away from modern brass alloys...ESPECIALLY thin sections.!!
Click to expand...

Great learning stuff. So far i learned that for brass blackening there are many options. I already got some of the solutions to do the blackening job, suggested on here an in another thread.

I didn't have any idea of the Ammonia effect on brass.

Thank you !!!

My problem wasn't the blackening method by itself. My issue when I started this thread was "how to clean the protective film" that brass photo etched parts have to allow the blackening products do their job.

I got very nice answers to that question and I ordered some of the suggested products. I will see if this week I have time to test them. Because soon I will have to blacken some photoetched parts.

Nevertheless, these postings about ammonia are highly educational for me and I belive for many others.

Thank you for taking time to write them.

Have you all an excellent day !!!

Daniel
 
Jimsky said:
A very good tip from our member @janos to lightly rub blackened barrels with graphite powder. It will for sure give that gunn effect.
Click to expand...

Jimsky.... just rub and that is it ?

By any chance, have you saved the link to Janos posting ?

I will start to cut and paste all these excellent tips in a word document for years to come.

Best
Daniel
 
I can try to find the link, but have tagged Janos in my post, so he may respond himself. But, believe it is as simple as this: with both fingers lightly rub using graphite powder. If you rub hard, you may remove blackened surface. The 'blackened' process is chemical reaction it is affect only very thin layer.
 
Dematosdg said:
Jimsky.... just rub and that is it ?

By any chance, have you saved the link to Janos posting ?

I will start to cut and paste all these excellent tips in a word document for years to come.

Best
Daniel
Click to expand...
Yes.... pretty simple.
After blackening, rub a little graphite around the ends of the cannons (the muzzle, the “business end.”). It adds a slight “graying” look...like burned gun powder. Indicating the cannon had been fired.
You could do this with a lead pencil maybe, as well as powdered graphite. Don’t want it to be neat and even. Irregular and splotchy looks real.
Thanks to @janos and @Jimsky for this idea.!!
 
This is what happened to some rings with over exposure to ammonia. The barrels seem fine. As mentioned by hobbit99, be very careful. I did try some rings with much less exposure (a few hours), which were ok but it's probably not worth the risk , if they can get brittle later. The below shown rings only cracked as I was trying to open the rings, if you don't need to apply pressure, they may be ok. I tried this method on hatch hinges with good results. All good advice on this site here.


P1070054.JPG
 
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