What does one need for Cryo treatment

Fletch Helical

Fletch Helical

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Sep 29, 2009
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Not that I'm planning on getting one anytime soon, considering I don't even have anything to heat a blade let alone freeze it. But I was just curious as to what goes into being able to do your own cryo on your blades. I'm guessing you can't just put some dry ice in a cooler and put your blades in there, so what actually goes into having your own setup.
 
I haven't done it before but from what I've read common setups usually include either Dry Ice floating in Acetone or Liquid Nitrogen.

I work a lot with Liquid Nitrogen and if I was going to be doing a lot of cryo treatment I'd go to Bay Airgass and get a tank. only problem is Liquid Nitrogen can be expensive, especially the deposit on the tank. but if you know someone who works with it you can transport it in small quantities in a well ventilated cooler, just try not to suffocate on your way home :eek:

on second thought, you'd be better off bringing the knives to the Liquid Nitrogen.
 
Some use a dry-ice slurry, or even two large slabs of dry ice that you sandwich the blade between in a styrofoam cooler for around -100F.

I picked up a liquid nitrogen dewar on this site a while back from a memeber who works in the biological sciences. He had 5 or so of them for sale, and I got a pretty good price. Keep an eye to ebay for a small/medium dewar or even check with local cattle operations. When I have a run of knives I need to heat treat (and cryo), I plop the dewar in the back of a pickup and go to the local Airgas to get it filled. It's not that expensive to fill relatively (if you're doing a run of 5 + knives), and the LN lasts in usable quantities for about 6 weeks in my dewar.

Do not carry LN in any sealed container as it WILL explode no matter the strength of the container. Also, don't transport it inside your vehicle with you as it could displace oxygen given long enough time. Most places won't even fill a dewar for you if you are going to load it inside with you. Also, think if you had a wreck and gallons of -320F LN splashed all over you. :eek:

--nathan
 
GrizzlyBear said:
You'd be like that liquid metal terminator! LOL
Click to expand...

no joke, liquid nitrogen burns suck. I've never had a bad one but even a drop or two hurts.

and make sure you set down your cooler on an insulated surface. we have coolers designed for filling with liquid nitrogen here at work and we have still cracked the epoxy flooring several times filling them. they do better on bare concrete but to be safe I'd set it down on a piece of wood if you value your flooring.
 
FWIW, I've been told that dry-ice slurries in a plain old cooler are about 80-90% as effective as LN in a dewar, at a fraction of the cost, with fewer safety issues. Every maker and pro heat-treater I've asked has said either is worth using and will increase toughness and edge-holding on any cutlery steel, to varying degrees.

Dry-ice is available from my local welding supplier for about the same cost per pound as regular H2O ice, which surprised me. They have it in blocks or chips. Experienced makers have advised me to use the chips.

I've been advised to use isopropyl alcohol instead of acetone to make the slurry; it doesn't last as long but is a good deal safer (cheaper, too). Under similar conditions, iso generally burns if exposed to a spark; acetone goes BOOM. Acetone stinks a lot more, too.

Be careful, regardless.
 
I believe dry ice and LN are essentially equally effective. The dry ice is easier to handle, but it will be gone in 48 hours or less. Liquid nitrogen in a dewar will likely last a month to six weeks. Around here, a cooler full of chips is about the same price as a dewar fill - and the xtra life saves many trips to town.

Dry ice chips can be bounced around in your bare hands hot potatoe style. Not a good idea with liquid nitrogen. Having said that, LN deserves respect but not fear. It really isn't isn't all that nasty unless you do something stupid - like pop bottle bombs. :rolleyes:

Rob!
 
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