Developing the blackened edge on San Mai

G

GrenfellsBrutalForge

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May 23, 2016
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Hello everyone,
Going to be doing some more San Mai probably this week. The steel will be 1095 core with a mild steel jacket.
I'm wondering if anyone can explain to me the process of getting that blackened edge?
I don't have ferric chloride, would have to order it but that's probably not happening any time soon with the postal labour dispute here. I have access to household acids like vinegar and lemon juice and I'm able to get muriatic acid locally.
I'm assuming you etch to develop it. What grit should I take it to before etching and after?
I usually don't like to go much beyond 600g but I'm thinking I'm going to need to go higher here?
I have the means to go as far as 5000g.
And help is very appreciated.
Thanks,

-Colin Matthews
 
i love how the black edge looks. ( i have only used ferric) does it wear off during use ? how fast ? thanks.
 
Get a tube/bottle of gun blue. It will blacken the edge like FC will. Just wipe it on with a Q-tip.
Other acids, like lemon juice and vinegar, will also darken the edge.

For the finish with a mild steel san-mai, just go to 400 grit. The sides will scratch easily in use, so the slight satin look of 400 grit is good. The edge will look fine at 400 grit, too.
 
Do you have to lay the gun blue on carefully to follow the wavy line of the hard steel or do you sand the flats again after applying?
Would be awesome if it's that simple, I have gun blue on hand.
Thanks Stacy!

-Colin
 
I have been told that if you do it with hydrochloric acid with a small amount of hydrogen peroxide mixed in it will result in the effect you are looking for.
 
Any acid solution will work. Don't use a very concentrated solution of HCl. The peroxide in the solution will accelerate the oxidation by providing oxygen radicals and O2. This will make it darker faster.

Whatever you use, you can paint the acid on with a Q-tip, let darken as needed, and then wash and neutralize the blade well. After drying, carefully wipe the san-mai skin with 400 grit paper to remove any darkness above the edge. With some practice, you can only apply the acid to the edge metal.

Another way is to paint the san-mai skin above the edge with an enamel paint. Let dry, and then darken the edge with the acid. Remove the enamel with paint thinner or acetone. Clean the blade well and it will be done.

Always remember to neutralize the blade well after any acid treatment, as san-mai and damascus can trap moisture and acids that will come out to haunt you later on. Boiling in a TSP solution will work the best. Remove, rinse well, wipe dry, and dry in the oven above 220F. Some folks place in the oven at 250F for half an hour, then oil while hot.

However you do etching - after all work is done, liberally oil the blade, rub it in hard, and wipe off the excess. Repeat this every time you do more work on the knife.
 
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