It Finally Dawned on Me Why a Hamon Shows Well After Etched -

R

rlinger

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Mar 29, 2002
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Even after I had to HT a set of damascus bolters for another maker because the soft bolsters would not etch to match the hardened blade it did not kick in to me. I've been looking at a couple 1075 blades that a freind gun maker of mine hot blued and was admiring how pronounced the hamon is compared to two other identical 1075 blades that are not hot blued and do not pronounce their hamon. So now, finally, I have a better understanding of why etching brings out the hamon. Oh well, just thought I would share my glee over that.

RL
 
The secret? Soft steel don't etch as well. The harder the more declarative.

(Did Chris call you last evening?).

RL
 
Thanks Roger, that's my experience too. Just wondered what hot bluing would do for it.

No, I didn't hear from Chris though I go to bed very early and might have missed his call. I'd like to talk to him though! Sounds like a decent sort, even if he does share some views with you. ;) :D
 
UH?; sounds to me like you know more than I :confused:. However, this ol'conservative ain't hurt even just a little bit ;). Chris Duda is real stand up guy, just like I told him you are Dave.

BTW, my answer to your question above, I hope you know, is the West Virginia two weeks before spring goobler season answer. Hopefully one or two of the ol'timers will chime in and give us the text book answer. I wouldn't mind hearing myself. It is curious to me.

RL
 
I have always noticed a deeper etch on the softer steel of my knives. I assumed that the hamon was brought out by the different rates in which the steel deteriorates under the etching solution. I thought it was that the hardened steel etched away more slowly and the softer steel etched away more quickly thus producing a hamon. Am I off my rocker?
 
That could make sense I guess. The more the etch the more dull in appearence. In that respect I would have it backwards as to my first comments. Thanks for that. Surely the text book guys will chime in before long.

RL
 
OK now to really mess with your mind... Fully hardened steel doesn't etch as dark as hardened-tempered steel :confused: . Some time ago metallographers found that extremely fine tempering carbides etched darker than untempered martensite, I assume that this accounts for the macroscopic effect that I have observed.

Annealed steel always etches a very grainy gray color and often needs to be etched quite deep to get a nice contrast. I do a low temp normalize/stress relieve on all my damscus fittings before etching. You may have encountered this headache- heavily grind your fittings with a course belt (like a 36X) and then polish all those scratches entirely away, heck mirror finish if you want, and then when you etch, to your horror those @#$! 36X scratches will reappear! :mad: Coarse grits will deform annealed steel enough to induce strain in the material. The stored energy within the metal will increase its susceptibility to corrosion- the ghosts of those scratches will stick around and haunt the fittings :eek: Heating things to 1000F or more, will result in what is called "recovery" wich is the anhilation of that residual strain. It will also allow things to etch a little better than if it were fully annealed- thats my tip for the day ;)

As quenched steel (65hrc) tends to etch quick, as far as topography goes (lots of strain energy there) but it etches lighter. The more you temper those needles, the darker the etch seems to become. I have found hundreds of variables in etching, only a few of them will do what you want :( . A fresh etch mixed with body temp. water will bite the fastest and the darkest, and the treatments you apply to keep the etch colors there are equally important.
 
Among other beneficial teachings, a most explanitary support for stress relieving. Thank you Kevin. Your post, perhaps not your primary intention, should go far in support of no short cuts in properly heat treating. I hope all, including myself, re-read your post several times.

RL
 
I was also told by NC-Cooter that adding hydrogen proxide to a weak / old etchant will revitalise the oxygen content and refresh the etchant. I still have to try that when my etchant shows that it is slowing.......
 
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