Coffee etch clarification

L

lanternnate

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Nov 5, 2016
Messages
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If I understand correctly, the coffee etch is done after the ferric etch, and it is really just to increase the contrast not truly an etch. I’ve also figured out that the ferric etch works best in short spurts cleaning the blade off in between to make sure there is a clean even etch.

My question is, should the blade be cleaned between the ferric and the coffee to get good coffee to blade contact, or is the blade left with the black from the ferric on when it goes into the coffee to have that black “set”? Follow on, do you do intervals with an in between clean once in the coffee or just just one long soak?
 
Leave the black
I do one long soak, and soak time depends on a number of things, ambient temperature, strength and age of the coffee, possibly variations in local water quality. I'm not sure if anyone's been curious enough to try different brands.
My soak times for me vary from 2hrs (in summer) - 8 hrs (winter), and that's purely temperature related, as I'm still using the batch I made over 2 years ago.
Don't worry about leaving it too long, because the worst that will happen is you stain the nickle steel and that scrubs off, and you can re-do the darkening.
 
I just thought that perhaps I should add: You finish the knife just like normal damascus, using the acid, neautralizing it and then using really high grit (I use 5000g sand paper with a hard back) to shine off the 15N20. Many people just end here and then give the blade a coat of oil to help prevent rust. You do the coffee as an extra final step before 'sealing' the color.

Depending on the use of the knife, you can do other things to preserve the pattern (blueing, Parkerizing, etc), but coffee is the only think I know for kitchen knives is the only way to darken the pattern and still remain food safe. The main negative is that how you clean the knife determines how long the pattern lasts before having to re-do the coffee to bring back the pattern. What I do is: (1) rinse mine off immediately after use, avoiding the scour pad and trying to use as little force as possible (thus the rinsing immediately after use), (2) PAT dry as best as possible, (3) let air dry the rest of the way before putting it away (I have a wood stove, and I put mine on top of that to dry the final bit, but this is unnecessary).

Have fun!
 
As far as I know, it doesn't prevent corrosion per se, but the forced oxidation of the steel does provide a barrier to slow further oxidation.

Please correct me if I'm wrong.
 
Would you get better results with a hot bluing process? What benefits do you get soaking a knife in coffee? I know it darkens the metal but would it eventually wear off?
 
In my opinion, it is merely a cosmetic look to get a black and shiny blade. I haven't seen a coffee etch that was durable in use.
Parkerizing or bluing is more durable. Cerakote or other epoxy blade coatings are also suitable when you want a dark surface.
 
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Yes, it does wear off, but in my experience, it's mainly dependent on how much you scrub the blade. The best benefit is that it gives a good, food safe dark blade and can be redone with the handle on.
 
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