Burnt Silk Metal Finish

[Stanley Covington]

Last night I finished working up a set of chisels I purchased here in Tokyo for my son. The kanmuri and kuchigane were originally bright steel with clear lacquer. Very unattractive. I refinished them with a very traditional but little-known treatment using silk that you may find interesting. This is not a smooth, uniform finish like hot blue or rust-blue or paint, but is much more interesting and attractive in my experience for this particular application. It is also easily accomplished. Warning: if you aren't careful, you can burn your fingeys, or even worse, if you do it in her kitchen and the range hood is not very powerful the odor may drive your wife temporarily insane possibly forcing her to use your money to buy an all-expenses paid vacation in Hawaii for some lucky attorney (may they burn in hell forever amen...).;)

1. Remove the kuchigane and kanmuri.

2. Heat them on a gas stove until just past the point where the metal turns blue. A camp stove outside is safest due to the smell. A propane torch will also work.

3. Holding the metal with pliers (I like needlenose), scrub the metal with a steel or stainless steel brush to remove oxidized particles of paint or oil.

4. Reheat. How hot? Idunno. If it isn't hot enough, the silk will not melt/scorch/stick properly. Too hot and the silk will bubble and crater. Somewhere past blue, the metal will turn greyish. That seems to be a good point.

5. Wad the silk into your off hand thick enough to protect it from the heat. Be careful.:eek:

6. Wrap/rotate/wipe the hot metal in the silk. The silk will smoke and scorch. If it doesn't, you don't have it hot enough. Remove the metal before it cools enough for the silk to build up too thick a layer or globs will adhere to it.

7. Quench the metal in water.

8. You can leave the metal as it is, or use a SOFT, FINE bristle steel or stainless steel brush to remove loose particles. A bit more polishing will burnish it. Too much and you will cut through to bare metal. If that happens, simply reheat and reapply.

9. Apply oil to the dry metal to prevent rust. The silk carbon will retain oil without softening, and is a very effective rust-preventative.

Warning: don't use this treatment on heat-treated metal unless you want it to go soft.

I love this finish. Some won't. Give it a try.:D

Stan

[Jonathan McCullough]

Ooh, I'm a sucker for the mystique of the orient and love to have another tool tinkerer's technique. This looks to be an interesting treatment for tool steels. But I have some questions. Kuchigane = ferrule or tang? Kanmuri = hoop? I take it you're not suggesting we give the actual chisel this treatment (unless, is it part of the tempering process for some Japanese chisels?). Is there some intrinsic oiliness about silk that makes it preferable to something else like, say, paper or cotton?

[Stanley Covington]

Ooh, I'm a sucker for the mystique of the orient and love to have another tool tinkerer's technique. This looks to be an interesting treatment for tool steels. But I have some questions. Kuchigane = ferrule or tang? Kanmuri = hoop? I take it you're not suggesting we give the actual chisel this treatment (unless, is it part of the tempering process for some Japanese chisels?). Is there some intrinsic oiliness about silk that makes it preferable to something else like, say, paper or cotton?

Don't know about mystique, but it is unusual. I understand it was a common finish for tansu and sword hardware prior to the chemical methods available nowadays. It was taught to me by a sword polisher many years ago.

If you use it on anything with a cutting edge, expect the edge to be ruined. If it is metal that needs to be hard to do it's job properly, expect it to no longer function. Kuchigane and kanmuri are mild steel. Soft is fine. I hope that's clear enough.

Sorry for the romanized Japanese. I don't know these terms well in English. As you say, Kuchigane (mouth metal) = ferrule. Kanmuri (crown) = hoop.

Oiliness isn't the issue. Silk is a protein produced by caterpillars, and when it get's hot, for a brief moment it melts, sticks and then turns to carbon. Some of this carbon gets infused into the metal. Some of the carbon adheres to the surface. This stickiness is something that paper and cotton don't have, even though both turn to carbon when heated.

If you practice and get the procedures and temperatures down perfectly, you can create a smooth, matte or satin-finish black surface. I've been able to do that a few times. But I can get that appearance with rust bluing or out-of-the-bottle bluing. The way I have described is simple, but it creates a very unique finish with a lot of character. Not for everybody.

[Bob Strawn]

It seems logical that breathing hydrogen cyanide would be unpleasant. You wife is quite wise to not like the smell of burning silk.

I would advise extraordinary ventilation and knowing where the vapors were going.

Bob