I have some SS knives and some gun parts that I would like to DIY darken. I don't need them to be dark black, I just want to darken them somewhat so they are not so shiny and reflective. Can you use brass black to darken up stainless a little bit.
I'm more interesed in a non-dimensional finish, somehting that works room temp or that can be set up w/ a torch or regular oven.
Birchwood casey makes a bluing solution also something called presto black but they both say they are for non-stainless ferrous metals.
I thought I heard you could use brass black on stainess, even though it only talks about brass, bronze and copper.
Many people/makers etch dark logos or designs into stainless, using etching solutions made for the purpose. Might be able to adapt that (in a diluted form, perhaps), for dipping/soaking/painting the blade in the solution? Just an idea.
soot from a flame?
If you heat hardened steel you will destroy it.
A coating or rough sanded finish is the only ways I know of for stainless steels. Gun blue and other like products will not work.
H2SO4, which you can find in car batteries (and therefore at many hardware stores).
You should get a more or less dark grey afterwards and you'll have to experiment a little bit with the percentage of the acid and the time you leave your object in there.
If all you want to do is knock the shine/polish off sand/bead blast it. Most machine shops have a cabinet and cost should be minimal. It does darken it a bit also.
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will sulfuric acid eat up you edge?
Pure sulfuric acid would be a liquid - but I dont know how to get it in the US.
I would try using the stuff from a car garage or a hardware store which is supposed to be used for battery acid.* Concentrated acid may not work (i'm not sure anymore) but.. anything between 30 and 70% should do the trick.
Of course: Be careful. Put the acid into some water - not the other way around. And dilute it when you're dumping it.
IIRC most drain cleaners are made of chemical bases - not acids - and I'm not sure if they work for forcing a patina.
It should work just as forcing a patina on carbon steels using weaker acids - so the very edge of knives will get weaker, too, but if you check the blade from time to time the patina layer shouldn't get too thick.
But yes, it probably wont shave as good as before and you may need to resharpen/at least strop a little bit.
Good luck! And again: be careful... can be dangerous stuff and it's easy to underestimate it... ((safety) glasses?)
*: the liquid in car batteries is supposed to be diluted sulfuric acid - so about 10-20%. Since it's possible to dilute it with destilled water I assume they'll sell the acid at a higher percentage (33% ?)
I dont know what I'd do if that doesn't work - probably trying to get stronger stuff (but still H2SO4) and leaving the objects in there for a longer time.
Last edited by s_f; 01-05-2011 at 02:55 PM.
I have a sandblasted 154cm blade, and after you oil it, it is rather dark grey. Could try that.
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