Caustic soda on damascus?

Will52100

Will52100

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Dec 4, 2001
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Any info on using caustic soda to darken damascus? How long to soak, how concentrated a solution? Watched a video and after etching, the damascus was put in the caustic soda for a while and it turned it black. After a 2000 grit wet sand to the high parts it came out beautiful, bright silver and black.

Thoughts?
 
Probably would work but that's another very strong chemical to use. If the item is carbon Damascus and immediately after being etched is handled carefully so as not to disturb the area wanted to be darkened placed overnight in a solution of water and lots of baking soda it will be a very deep black even after wiping off with paper towels.
Frank
 
Sodium Hydroxide AKA "Caustic Soda is used to clean Radiators it is a harsh chemical much worse than Acid in some circumstances. Be very cautious of chemical burns....this stuff will dissolve aluminum before you eyes. The other caution is Hydrogen Embrittlement where the Hydrogen molecule dissolves into steel and can cause cracking under heat treating and steel processing.
 
The leaving in baking soda overnight, how tough is the black?

I've used caustic soda while offshore, mainly caustic soda beads and mix to add to mud, and it's not a pleasant substance to work with at all. I was hoping the caustic soda would not need to be as concentrated as what I've used before.

Thanks
 
In fact it gives a very good black finish after being oiled several times. Certainly as good as anodizing a metal. Sorry I can't send a picture.
Frank
 
I would stay away from CS. Personally I etch until I get the look I want and then put the blade in a pot of Trisodium Phosphate and let it boil for 10-15 min.. This neutralizes the acid and "sets" the etch. Baking soda will work as well.
 
If it was boiling caustic soda you saw, that process is known as hot bluing. A mix of caustic soda and a nitrate. Its a VERY strong mix, imagine a tank of boiling drain cleaner, if not even stronger.
It does a beautiful job, but definitely isn't risk free. Same way firearms are typically blued.
 
Actually it was a room temp solution, and clear as water. No idea the concentration, I imagine it's a bit weaker than what I used as a derrick hand, but still not something I liked working with.

I'll give the overnight soak in backing soda a try, thanks for the tip.

What I normally do is etch for 10-15 minutes and scrub with 0000 steel wool that's been de greased and etch again and clean again until I get the look I'm after, most times three etches/cleanings. I just saw the results of the CS and thought it looked good. If I can achieve the same result from soaking in baking soda overnight that would be a plus.
 
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I can get real caustic soda but after using it once or twice I went back to the ferric chloride and the overnight or so in the backing soda. I'm pretty sure you will like the results. Use your "regular"etching time and it happen for you!
Frank
 
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