Why didn't the entire blade color?

weo

weo

Joined
Sep 21, 2014
Messages
3,109
Hello all. I just finished this blade (minus the final edge) and like the title says and the pictures show, the blade area right at the heel of the blade doesn't take the coffee stain like the rest of the blade.
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This isn't the first time I've come across this. When I first came across this, I thought it might be that the blade didn't fully harden there, but I'm pretty sure that's not the case.
Thanks
 
Still got a lot of decarb on that blade. Also, coffee is a coating more than a stain. The blade should be acid etched ( or heavily FC etched) before the coffee so it has something to hold onto.
 
Thanks, Stacy. That's not decarb, but rather scratches from sanding to only 800g. I wanted to try a lower grit on this blade to see the difference. I know it would have been easier if I did this before putting on the handle, not sure why I didn't. I'm now thinking about taking the time to take pics of the stained blade after 1000g and 2000g for future reference.

Also, thanks for explaining how coffee works. Are you're saying it's the same stuff (grounds) that's at the bottom of your coffee cup just in a much finer form? Like staining your shirt when you spill coffee on it?
 
Weo, I think what Stacy is saying is that the silvered areas, the stuff that didn’t stain, are decarb.
 
Weo, you might want to explain what the blade is. Pretty sure that’s 2 different steels guys.
 
OK, I see the crescent at the heel he is talking about now. I missed it and thought he was talking about the blotchy looking areas.

The place at the heel could be not fully cleaned and have some contaminate from the grinding steps, or maybe a tad of the layered metal ( if that is two steel types).

From what I understand, coffee "etch" is a predominantly resinous buildup on the surface caused by the coffee. It etches a bit into the steel, but mainly is above the surface. It rubs off some areas easily, which may be what happened at the heel. My friend who does coffee etches on long blades says he heavily etches with FC, cleans the blade well, then does the overnight soak in crazy strong instant coffee. It will still rub off with any abrasion like a polish cloth or rubbing with your fingers hard.
I believe I read where some folks give a quick etch in HCl , rinse and neutralize, and then do the coffee "etch".
 
Thanks all. And sorry for leaving out that it's an O1/15N20 blade.
 
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