Strange Hamon, what's going on with this blade does anybody know?

L

Londinium Armoury

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Jun 2, 2020
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Okay so I'll post video of the blade to make this easier, I have no idea what's going on with this hamon, I've never had this happen before. One side of the blade seems to be "Alright-ish" but the other side is blotchy, and seems to have strange irregular patches.


Did water or steam get underneath the clay? it looks like some of the blade might have hardened in strange patches, one side seems almost uniform except a patch near the upper flat towards the tang end. Then there's the other side which is all over the place. I tested edge hardness and it seems to be fine, I don't have a HRC tester to test for exact numbers, but the edge is hard and the spine is softer all over. Except it looks completely weird, what's going on exactly with this blade, I did everything normal the way I usually do it.

Maybe the clay was too thin on one side? or too thick?
 
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One possibility is decarburization. I am not an expert, and these details may need correction by more experienced smiths.

The regions that are splotchy, or not etching as dark, may have had more carbon removed while heating. This would result in more Ferrite, as opposed to martensite or pearlite. This different structure would etch differently - probably lighter.

If that is the case, the solution would be to grind away more material from the lighter regions and etch again. This would remove the decarburized outer layer.
 
FunkCoaster said:
One possibility is decarburization. I am not an expert, and these details may need correction by more experienced smiths.

The regions that are splotchy, or not etching as dark, may have had more carbon removed while heating. This would result in more Ferrite, as opposed to martensite or pearlite. This different structure would etch differently - probably lighter.

If that is the case, the solution would be to grind away more material from the lighter regions and etch again. This would remove the decarburized outer layer.
Click to expand...

Thanks I didn't think of that, I'm out of Ferric until my next batch comes in the post, so i've been leaving it in apple cider vinagar overnight, which isn't helping with the etch.
 
Londinium Armoury said:
Okay so I'll post video of the blade to make this easier, I have no idea what's going on with this hamon, I've never had this happen before. One side of the blade seems to be "Alright-ish" but the other side is blotchy, and seems to have strange irregular patches.


Did water or steam get underneath the clay? it looks like some of the blade might have hardened in strange patches, one side seems almost uniform except a patch near the upper flat towards the tang end. Then there's the other side which is all over the place. I tested edge hardness and it seems to be fine, I don't have a HRC tester to test for exact numbers, but the edge is hard and the spine is softer all over. Except it looks completely weird, what's going on exactly with this blade, I did everything normal the way I usually do it.

Maybe the clay was too thin on one side? or too thick?
Click to expand...


You didn’t get through all the decarb.
 
Willie71 said:
You didn’t get through all the decarb.
Click to expand...

So that's really all it is? it's a bit hard to sand off, I don't think I can even draw file it properly it kind of still skates the file on the edge. I might take it to a belt sander or grinding disc then, hope I don't take too much off near the edge it's getting kind of thin.
 
My first thought was that the blade needs more sanding/grinding . Hamons often look much different after the decarb is removed and the surface is properly sanded. I rarely pay much attention to how it looks right out of the quench tank, or even after the initial scale/decarb removal.
 
Stacy E. Apelt - Bladesmith said:
My first thought was that the blade needs more sanding/grinding . Hamons often look much different after the decarb is removed and the surface is properly sanded. I rarely pay much attention to how it looks right out of the quench tank, or even after the initial scale/decarb removal.
Click to expand...

I left it in a vinagar bath for another 24 hours just to see if it showed more, but it just made the already visible part more pronounced and the rest was still hidden. I'm going to remove the acid wash and take it back down to 120 grit and start the sanding process again. I have a few D2 blanks that I have to put scales and pins on first, once I've done them I will try dealing with this hamon sanding again. Thanks again, so the consensus is all agreed that it's a decarb and lack of sandng problem, that's good to know.
Cheers guys.
 
After the quench you need to remove a reasonable thickness of metal to expose the clean hardened metal. This layer is sometimes called the "skin". It is a layer of decarb which varies in thickness. The tip area has the most usually. Just sanding the blade to a shiny metal doesn't get rid of this layer. You have to remove about five to ten thousandths of an inch. This is part of why you leave the edge at .030" or thereabouts - so you can re-grind the whole blade and remove the skin while creating the proper edge.
 
Stacy E. Apelt - Bladesmith said:
After the quench you need to remove a reasonable thickness of metal to expose the clean hardened metal. This layer is sometimes called the "skin". It is a layer of decarb which varies in thickness. The tip area has the most usually. Just sanding the blade to a shiny metal doesn't get rid of this layer. You have to remove about five to ten thousandths of an inch. This is part of why you leave the edge at .030" or thereabouts - so you can re-grind the whole blade and remove the skin while creating the proper edge.
Click to expand...

Ah so that's why all my hamons are not coming out as pronounced, I thought it was due to 1095 manganese levels, or me not using ferric chloride to etch. I might go back and take a larger layer off then, they probably have much nicer hamons hiding under the surface after all.
Thanks again.
 
All preliminary togi has to be done and the blade scrupulously clean before working the hamon.

Long soaks will tend to over etch. On a hamon it is all about a subtle etch. Try lemon juice. Warm the blade a tad (100°F/40°C) and work the lemon juice with a cotton ball along the hamon.

Doing shiagi-togi to brighten or darken the ji above and below the hamon will also make it stand out better. It is in this work that you remove any over-etching.
 
Stacy E. Apelt - Bladesmith said:
All preliminary togi has to be done and the blade scrupulously clean before working the hamon.

Long soaks will tend to over etch. On a hamon it is all about a subtle etch. Try lemon juice. Warm the blade a tad (100°F/40°C) and work the lemon juice with a cotton ball along the hamon.

Doing shiagi-togi to brighten or darken the ji above and below the hamon will also make it stand out better. It is in this work that you remove any over-etching.
Click to expand...

Thanks, I've been using apple cider vinagar after polishing to a fine grit. I was just removing too little before going to the polish, I think if I go back and take more off then start the polish from scratch then do the lemon juice method it will come out nicer, I hope. I have a bottle of pure lemon juice in the kitchen, usually for pancakes, buit now it has a higher purpose maybe.

Cheers.
 
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