View Full Version : Finally... cryo and temper lines


Jason Cutter
05-05-2003, 05:29 AM
Finally, swopped photos from yahoo to fototime.com. Hope I have more success with this photo server. It hasn't let me down yet. yahoo was a disaster. Even I can't get into my own photos 3/4 of the time.

I was talking about doing cryogenic treatments on carbon steels and it technically should help the martensitic conversion also. But it might also have an added bonus for those of use who do selective hardening, eg.- clay backed quenching etc. The temper lines seem to show up a lot better and they get so crisp it looks like it has been drawn in with a rough pencil.

Please note that I am using a "home" cryo - deep freezer at minus 10 degrees Celcius in my freezer. I do a standard clay backed quench, full temper at 375F 90minutes, freeze for 48hours and destress at 325F for 60minutes for even touching it again in the workshop.

The finishing technique is similar on both knives - the result is quite different. The hamon on the first is a traditional Japanese hamon - no cryo. The other is with the cryo. Both were lightly etched up in ferric chloride and then polished back going up to 1500. The hamon on the second is even more crisp than the photo can show. I've made more knives with the cryo since and the hamon shows up extremely clearly even straight from the grinder.

http://fototime.com/ftweb/bin/ft.dll/standard?pictid={BF978F13-91C0-47D9-AD14-EE17D8BF1A8B}&exp=f&moddt=37746.4297357986

http://fototime.com/ftweb/bin/ft.dll/standard?pictid={48B54CB0-4004-4ACE-930A-7E55DB58D9A8}&exp=f&moddt=37746.429728206

I'd love to hear your input and experience with this sort of thing. Thanks. Jason.

Sethhoward
05-06-2003, 08:16 AM
Jason,

Thanks for posting those pics! What are you using for clay? Are you quenching in water or oil?

I seem to remember reading somewhere about going from hardening to the freezer then the temper. Any thoughts on possible different results depending upon when the cryo takes place?


Seth

Jason Cutter
05-06-2003, 02:57 PM
The clay technique - I use liquid / paintable refractory cement and simply apply to the spine area approximately where I don't want any hardening and ensure that the edge area is ABSOLUTELY CLEAN of refractory - it is very effective as a quench block. Ie.- quite different from traditional clay coating. Creating the pattern requires experience in manipulating the position of the clay. Applying the clay is easy, but go slow as the clay takes a very long time to dry and if still wet can bubble in heat and fall off the blade.

The forge technique - the heat up is about 3x as long due to the heat block effect and you have to pay special attention to the bit near the ricasso to get a clean drop in the hamon as the thicker ricasso acts as a heat sink and draws heat away. There is always a chance you don't get that bit up to critical.

The quench technique - standard oil quench. Water quench - too much warpage and chances of breakage. Its more applicable to the traditional method where the entire blade is covered in clay as well. I designed this technique to be used with a standard oil quench - whatever you are already using is fine as the edge portion is not covered.

Back to the cryo -

I haven't done enough experimentation to make any statements about the other techniques (They are continuing on my test blades.) I am confident that the current method of cryo works - quench, full temper, cryo, snap temper, for performance, thats why I this blade is already sold and is on its way to its new owner now. Overall, its hard to make enough blades to experiment since I don't want to be selling knives with any unknown / experimental factor. I'll keep you guys posted about those experiments if you like.

Cheers. Jason.

whv
05-06-2003, 07:17 PM
always appreciate ongoing experimental results, kwong. looks as if you have a good thing going.
thanx

Misque
05-08-2003, 11:39 PM
Jason,
I gotta tell ya, I'm a bit stunned at the difference in those two hamons.:eek: I'm really glad you got those pics to post. I've been chomping at the bit to see them.
I am very interested in any performance differences you might discover so PLEASE give us updates of your experimentation.

Thank you for sharing!

BTW, dude your knives ROCK!!


All the best,
Mike U.

whv
05-12-2003, 07:47 PM
welcome to ckdf, mike.

Misque
05-13-2003, 08:16 PM
Thanks Wayne! This is one nice site ya'll have here. I usually haunt BFC and KFC but am finding myself rushing thru them so I can get here.:D


All the best,
Mike U.

Sethhoward
05-15-2003, 11:33 PM
1084. 6" blade. Temper, Cryo, Temper.

http://members.cox.net/sethhoward/hamon2.JPG


Any ideas in best etchent mixtures for hamon lines?



Seth

Jason Cutter
05-16-2003, 12:14 AM
After some recent emails back and forth from you guys, I tried some other types of etchants that may or may not be useful for my personal uses. Many seem to use vinegar.

For the moment, I'll keep using the ferric chloride dliuted 1 part ferric in 3 parts water as it seems the most predictable for me. A lot of my finishing techniques are based on how long I dip in feric etc. A deep etch is not necessary and the temper lines shown above are achieved with only a "quick" etch (whatever that means). What determines the final finish is equally importantly related to what you do after the etch.

Thats a nice blade by the way, Seth. Technique ?

Cheers. Jason.

Sethhoward
05-16-2003, 03:53 PM
Forged and flat ground. It was a 14th cen. reproduction untill I got curious about hamon lines. Now.....

Not very clear in the picture is a second temper line a quarter inch or so up from the clear one. I think it might have been from soaking at critical temp and the heat creeping up under the clay a little. I etched and sanded this poor blade about eight times just curious as to what changes it would make in the hamon. The second one came out about etch five.

How are people etching to get the hardened area dark and the back light? It is just the opposite from these ( Jason's and mine). I am not sure which I like more.


Seth

Jason Cutter
05-16-2003, 04:40 PM
Seth, the second hamon is something that I see on EVERY SINGLE BLADE I DO THESE DAYS. I'm not clear what it is, or how to explain it, but its there. I think you're right. It may be the second hardening line due to a "second" quench that happens even though the clay is supposed to be a complete heat/quench block. In basic {workshop} hardness testing, the spine is still always nice and soft, and performance testing still works out. The presence of that second line doesn't interfere with the clarity of the main hamon you have tried to make. Perhaps others can answer that question.

For a finish are you just doing etch and sand back to highlight ? Thats the traditional approach that I'd being trying to get away from. Try this - use a piece of leather paddle or tissue paper with lots of red oxide rouge buffing compound and rub the blade vigorously (carefully not to get slashed up) and the finish will start to change fairly quickly. It helps to dissolve a bit of the compound with some methylated spirits. The rouge buffing compound contains iron oxide which differentially oxides the surface.

You can do that several times and it will eventually polish the blade - the hardened edge area will get shiny and dark while the area above the hamon goes a frosty milky white. The hamon itself will start turning white. Play the blade in the light and the different areas change colour.

Hope that makes sense. Jason.

Mark Van Loon
05-16-2003, 10:07 PM
that second hamon you are seeing might be what is called utsuri, its hard to tell from pictures alone. utsuri sometimes occurs when the egde of the blade reaches a higher temp than the middle, and the middle is a slightly higher temp than the spine. its supposed to kinda of mirror the hamon. in japanese blades it is a somewhat desired effect. i have noticed it on a few of the test blades i have quenched

Sethhoward
05-19-2003, 09:40 AM
Jason, you are correct. I was etching in a mixture of acid, water, and vinegar ( soaking for 3 to 5 min ) and wet sanding with 1000 grit. Last night I did a very quick etch by applying the etchant with tissue and the polishing with SemiChrome. I got a similar result as to what you were describing above, shiny edge and cloudy blade.

Using the red rouge method, no etch correct?


Seth

Jason Cutter
05-19-2003, 02:52 PM
Seth, I found that the best way (for me) to get a clear hamon is to etch in ferric chloride then do the hand buffing off with the red rouge compound. I take the finish all the way up to at least 1500grit hand rubbed before the etch. 2000grit is even better. I etch for 2-3minutes, then neutralise and go straight to the hand buffing. Any more sanding might change the nature of the lines again.

If you don't etch, the hamon will also show, but it'll be much less prominent. A very, very quick etch vs. a deep etch will produce different results too. With 1500 or 2000grit before etch, the depth of the etch is more controllable too.

I think these alternatives would also work (same principle) :-

1) Final finish, etch with vinegar, hand buff with red rouge.

2) Final finish, etch with whatever, buff on the machine with red rouge, just enough to take off the oxide layer, then hand buff with red rouge.

Lots of ways to skin a cat. Jason.

Sethhoward
05-22-2003, 01:31 PM
I have seen knives that have a milky edge and shiny back and some just the other way around with a shiny edge. What is being done differently to get the opposite effects?

Seth

Jason Cutter
05-22-2003, 02:07 PM
The traditional Western method is to etch then finish by using the finest paper you have (eg.- 1200 / 1500) to take the oxide off and scratch the steel underneath. The effect is a combination of what you get when you etch and sand back damascus to highlight, and the different depth with which the hard-soft steels scratch with sanding. This seems to produce a darker back than the edge. The temper line itself, if etched appears a deep black - grey.

The traditional Japanese method involves an etch while the polishing technique is being used. The waterstones are based on a limestone type rock and itself acts as an etch when used with water. When the very highly polished surface is further rubbed, polished with the furnace ?scale (can't remember the name) - this is essentially an iron oxide, this sets up a second set of oxidation processes which creates the shiny dark edge and milky back. The hamon and its associated activity appears a bright creamy white.

The process I have been using - taking it to 2000grit and etching with ferric (substitutes for the waterstones) and buffing back with red rouge compound which contains iron oxide (substitutes for the "black powder" polishing, seems to closely resemble the PROCESS of the traditional Japanese method.

This is what I understand of the CONCEPT of the technique. I am less interested in the specifics of the technique than the BASIS of the techniques.

I hope this makes sense. It didnt make any sense to me till a few months ago. Cheers. Jason.