Differentiating hamon colors

K

Kellan Peterson

Joined
Jan 23, 2018
Messages
8
Hello all,

I've been experimenting with clay and hamons recently on my knives and had a couple of questions for you experts out there. First off, I've noticed I'm getting different colors (darknesses really) below and above the temper line. All of the steel I have used so far has been 1095, but sometimes the blade appears darker below the temper line and sometimes its darker above it. Why is this? Is one better or more correct than the other?

Even looking through some Instagram photos of some pretty reputable makers, I've noticed it varries between them as well.

Any and all insight would be appreciated!

Thanks,


Kellan
 
Photos are pretty much a necessity to diagnose a problem with an etch or hamon.

Assuming you have properly sanded the blade and etched the hamon:
1) The two areas have different structures. The area below the hamon is martensite. Martensite usually etches darker than the upper part.
2) The upper part is pearlite ( and maybe some martensite in pockets or along the spine). Pearlite usually etches lighter.
3) The hamon itself is a mixture of the two structures (It used to be called Troosite). There are crystals of martensite in a pearlite matrix. They are called Nie and Nioi. Nioi are fine crystals and have a cloudy white look, and usually compose the hazy edge of the hamon. Nie are coarse crystals with a sparkly look. They are often found above the hamon in individual crystals or groups of crystals making clouds.
4) Decarb left on the upper bevels due to incomplete togi ( sanding/grinding) will etch gray.
5) Scale left on a blade due to incomplete togi will look black.

Comment:
About 75% of the blades I have seen done by new makers or those new to hamon have not been sufficiently sanded down. The lines and colors from the quench are covering the real hamon and its features. Another common issue is way too much clay.
 
I think like Stacy said the biggest differentiation between different makers coloring comes from a combination of how they heat treat, how much scale and decarb they create, and how much post HT grinding they do.

I do quite a few hamon and having learned how much material I need to remove to get through any scale or decarb my blades are always dark where hard and lighter where not hard in the broadly speaking.

Then there's the question of how the blade is etched and how it's polished and what kind of polish is used with an almost infinite number of variations that can create different "color" appearance to the finished blade, as well as how much carbon is left in a particular area post etch regarding light/dark.
 
Prior to grinding it is very common to see weird colors or shades on the surface of the steel. Martensite, fresh from the quench will often have any scale (or anti-scale coating) pop off due to the rapid contraction of the underlying material. When this happens, the underlying martensitic steel tends to be a light matte gray. The clayed portion of the blade, even after cleaning, will have some clay that didn't pop off, possibly some scale, and other things that may leave it a bit darker. After tempering, depending on how clean the knife was when it went into the oven, you can get some really crazy colors. If you are talking pregrind, there are a ton of possible factors.

If you are taking plane jane 1095, grinding, polishing, and etching, and you are seeing darker metal on the spine and lighter metal on the edge, the only reasonable explanation I can come up with is that the clay is protecting your spine from decarb, while the edge is decarburizing and so etches lighter than the spine. This also presumes that you are not subsequently grinding through the existing decarb.
 
Okay, this is a lot to take in. One knife I did, I just cleaned up with a surface conditioning belt. That blade wasn't very distinct, there was a faint black line which I assume to be the temper line.

The other blade I spent about 5 hours hand sanding up to 2500 grit. The hamon was very clear and the lower (hardened part of the blade) appeared the darkest. The time spent standing was well worth it.

Most of the information, graciously provided by the experts above, seems to be on par with my results.

Thanks for taking the time to help a new maker out! I'll try and post some pictures later today or tomorrow if I remember.

Thanks again!
 
Kellan Peterson said:
Okay, this is a lot to take in. One knife I did, I just cleaned up with a surface conditioning belt. That blade wasn't very distinct, there was a faint black line which I assume to be the temper line.
Click to expand...

Are you saying you heat treated it, and then just brushed it clean with a scotchbrite belt? If so I can almost guarantee you aren't seeing what's really there. You have to take off .010 to .015" each side to get past the decarb unless you're doing something to prevent decarb all together.
 
For example. Here's a blade I scotchbrited after heat treat.

WLLSK4F.jpg


Here it is after grinding down .015".

OGBTBBT.jpg
 
kuraki said:
Are you saying you heat treated it, and then just brushed it clean with a scotchbrite belt? If so I can almost guarantee you aren't seeing what's really there. You have to take off .010 to .015" each side to get past the decarb unless you're doing something to prevent decarb all together.
Click to expand...


Haha yes that's exactly what I'm saying. Its entirely possible that's still decarb on it. All experimental.
 
You must log in or register to reply here.
Back
Top