Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
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Knifemaker / Craftsman / Service Provider
- Joined
- Aug 20, 2004
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Ken, I agree that it is not a great significance since the exact temperature of DI is not needed. -70°F will be low enough for most situations.
DI is -110°F, a Blade in a DI slurry is -105°F, and loose DI chunks drop the blade to -70 to -90°F°F (depending on fineness of DI pieces). The finer the DI pieces the faster they sublimate and thus drop the surrounding air/CO2 atmosphere temperature. The difference is that the gaseous CO2 acts as an insulator between the blade and the solid DI, whereas the liquid alcohol is a conductor.
Technically, the best way to use solid DI to cool a blade would be to place the blade between two slabs of DI in a well-insulated cooler and leave it there for an hour. I am sure burying it in a cooler filled with DI chunks would cool it nearly as well. As we both agree, this is just technical semantics, and the real-world difference to the blade is small.
My DRYO method (I have never called it that, BTW. It is called a sub-zero bath.)
I use a "whole fish pan". It has a rack that is useful to lift out the blades when done.
I put in the alcohol to about half depth. I crush up the DI into small pebble size pieces and add the broken DI to the alcohol slowly. At first it will boil like crazy as the DI quickly sublimates. After a few minutes it settles down to a nice "simmer". As the temp of the alcohol drops you can add as much DI as needed to make a slurry. Since you can't store it, I usually add the rest of the DI when I am ready to start adding blades. I add the blades one at a time as I take them out of the quench plates and then cool them further in cold water. Quenching in oil/or plates and then cooling in a bucket of ice water will help keep the boiling down a bit, but you can put the blades into the slurry at room temp.
A word of caution:
It looks like a bath of alcohol when it settles down. The container may have frost on the outside (especially a metal pan), but that doesn't look scary. However, the bath is close to-100°F and will instantly freeze skin if you try to pick up a blade by hand. Rubber gloves aren't suitable protection. USE TONGS or a rack!
Fun stuff - After you are done with the blades and they are in the tempering oven, you can put things in the DI slurry remaining to have fun. Freeze a flower and smash it with a mallet. Freeze a rubber hose and break it in half. It isn't quite like LN, but if you have kids, it can be a fun way to show then the degree of cold you have created.
When the pan/cooler/etc. of slurry has sat around for a couple hours, give it a stir to release and saturated CO2 in solution. Pour it back in the can and give it a shake. Put the top on loosely and leave it sit until room temp, then close the cap tight. I label the can Dry ICE and use it over and over again.
DI is -110°F, a Blade in a DI slurry is -105°F, and loose DI chunks drop the blade to -70 to -90°F°F (depending on fineness of DI pieces). The finer the DI pieces the faster they sublimate and thus drop the surrounding air/CO2 atmosphere temperature. The difference is that the gaseous CO2 acts as an insulator between the blade and the solid DI, whereas the liquid alcohol is a conductor.
Technically, the best way to use solid DI to cool a blade would be to place the blade between two slabs of DI in a well-insulated cooler and leave it there for an hour. I am sure burying it in a cooler filled with DI chunks would cool it nearly as well. As we both agree, this is just technical semantics, and the real-world difference to the blade is small.
My DRYO method (I have never called it that, BTW. It is called a sub-zero bath.)
I use a "whole fish pan". It has a rack that is useful to lift out the blades when done.
I put in the alcohol to about half depth. I crush up the DI into small pebble size pieces and add the broken DI to the alcohol slowly. At first it will boil like crazy as the DI quickly sublimates. After a few minutes it settles down to a nice "simmer". As the temp of the alcohol drops you can add as much DI as needed to make a slurry. Since you can't store it, I usually add the rest of the DI when I am ready to start adding blades. I add the blades one at a time as I take them out of the quench plates and then cool them further in cold water. Quenching in oil/or plates and then cooling in a bucket of ice water will help keep the boiling down a bit, but you can put the blades into the slurry at room temp.
A word of caution:
It looks like a bath of alcohol when it settles down. The container may have frost on the outside (especially a metal pan), but that doesn't look scary. However, the bath is close to-100°F and will instantly freeze skin if you try to pick up a blade by hand. Rubber gloves aren't suitable protection. USE TONGS or a rack!
Fun stuff - After you are done with the blades and they are in the tempering oven, you can put things in the DI slurry remaining to have fun. Freeze a flower and smash it with a mallet. Freeze a rubber hose and break it in half. It isn't quite like LN, but if you have kids, it can be a fun way to show then the degree of cold you have created.
When the pan/cooler/etc. of slurry has sat around for a couple hours, give it a stir to release and saturated CO2 in solution. Pour it back in the can and give it a shake. Put the top on loosely and leave it sit until room temp, then close the cap tight. I label the can Dry ICE and use it over and over again.
I'm thinking I won't even have to weigh them down, or even clamp them. hahhah
