Chef's Knife with Hamon

Bush craft knives are great, and a perfectly fine product of knife making. However, there is nothing quite like the elegance, and the ubiquity of utility of a kitchen knife. Every one needs one, they each have serve a specific purpose, and can cost a considerable amount. 

All that together means I have to try it. 

The first knife every one needs is a proper chef's knife. It can handle any task in the kitchen, and in fact is used to handle most kitchen tasks.  For this knife I used 1095 steel for it's decent cutting ability and ease of sharpening. Another motivation to choose this steel is for it's ability to show hamon lines. 

A hamon is the result of a differentialy hardened blade that has been acid etched. The varying hardness in the steel causes the acid to etch differently, creating a hamon. This technique is primarily used in Japanese sword making. For kitchen knives, it's merely cosmetic. But it's dang cool. 

The basic process is simple, cover the spine of the blade in a layer of insulating clay (I used satanite). Allow it to dry, and then proceed with the heat treating as per normal. 

 

Diferentially hardening  causes some rather undue stress on the blade. So it's important that you take as many precautions as possible. My first attempt warped beyond repair, and I had to call the whole thing a loss. First of all, it's important that the bevel is not ground all the way. I'm using 1/16" stock, which I've decided is too thin to actually do any beveling prior to heat treat. If you do bevel before the heat treat, be sure you do the best you can to make them even. Variation in the grind will cause uneven forces to happen during the quench. 

Secondly, I did not do this for either blade. But a very common and supposedly effective method for differentially hardening is to cover the entire blade in clay, with a thicker application on the spine. This reduces the gradient of forces being applied and increases your chances for success. 

Once you've successfully quenched a blade,you can move onto the fun part - The Etch. 

I used ferric chloride acid to get this hamon. At first I tried using it full strength in a plastic tub that was too small. This caused some unfortunate discoloration where the blade was not fully submerged, and the level of concentration etched the blade too quickly for a decent looking hamon. I had to polish it out a number of times before I learned you're supposed to dilute the acid before you use it. That also gave me enough solution to fill a container that could actually hold the entire knife blade. I left it to etch for 5 - 10 minutes. But it's perfectly fine to pull the knife out of the solution, clean it off, check the amount of etching, and re-submerge it in the solution if it's not ready yet.

Acid etching steel causes a lot of oxides to build up. These are pretty easily removed with steel wool and dish soap. And the final little bits were vigorously rubbed out using flitz polish. I can't say if the polish was actually worth the effort. But it did clean up some of the final subtle darkening caused by the oxides.