Dry ice slurry help

Outdoor Gear Dad

Outdoor Gear Dad

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Jun 1, 2019
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Hello all, I am going to start messing with stainless. I’ve only been doing knives for 11 months now. I got my kiln in so ready to try stainless. I don’t have means to do LN, so was gonna do dry ice.

was planning on using one of those large plastic water thermos....you know the ones with the screw on kids that kids take to soccers games?

what should I be mixing with the dry ice? Kerosine, acetone? And what’s the ratios I should be using? Also how long does that slurry usually stay cold for?

appreciate the help!
 
I've been using denatured ethyl alcohol because it's much less volatile than some other options and won't react with plastics. (Acetone will dissolve most plastics.) I just crush up the dry ice fairly finely to make a slurry. As long as there's still some ice in the mixture then you should be cold enough. The finer your ice chunks are, the more surface area is exposed to the liquid and the faster it responds to a heat input and the less likely you are to be overcome by losses through the cooler. I've been using a very old, tired 4 gallon chest style cooler with about a gallon of alcohol and 3-4 pounds of dry ice and it's good for about 6 hours. A better cooler with less surface area would make it last far longer.
 
CallumRD1 said:
I've been using denatured ethyl alcohol because it's much less volatile than some other options and won't react with plastics. (Acetone will dissolve most plastics.) I just crush up the dry ice fairly finely to make a slurry. As long as there's still some ice in the mixture then you should be cold enough. The finer your ice chunks are, the more surface area is exposed to the liquid and the faster it responds to a heat input and the less likely you are to be overcome by losses through the cooler. I've been using a very old, tired 4 gallon chest style cooler with about a gallon of alcohol and 3-4 pounds of dry ice and it's good for about 6 hours. A better cooler with less surface area would make it last far longer.
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Can I get that alcohol at Home Depot? Also I will only be doing 2-3 blades at a time...you think I could use a lot less?
 
Not sure about a plastic container, it gets brittle in the cold. Denatured alcohol is what most makers are using with the dry ice.
 
This is what I'm using: https://www.homedepot.com/p/Klean-Strip-1-gal-SLX-Denatured-Alcohol-Cleaner-GSL26/100139444

You only need enough liquid to cover your blades and enough ice to keep the temperature down. If you have the right size container you could probably get a way with a couple of cups of alcohol and less than a pound of dry ice. Remember that the biggest use of dry ice will be bringing the alcohol and container down to temperature. Once it's cold, it will stay cold for a long time if you have a decent cooler and you don't open it and allow warm air in.
 
And once all the dry ice has sublimed you can just rebottle the alcohol for next time. The one danger is that you must let the alcohol degas for a while because if you don't and then you put it in a sealed container, it could release the gas and pressurize the bottle creating a bomb.
 
Just do be careful though - at room temperature denatured alcohol is not as flammable as say gasoline ... but it is still pretty darned flammable. It also burns with a clear bluish flame ... so in bright light it can be burning, and you actually can not see that it is on fire......
 
Fortunately, at dry ice temperatures the vapor pressure of ethanol is essentially zero so it is extremely difficult to ignite without a proper flame source, but once ignited it won't go out easily as the heat from combustion will produce the necessary gaseous ethanol to continue combustion. That being said, if your cooler of ethanol ever does catch on fire, just close the lid and it should go out long before it could melt through the cooler.
 
CallumRD1 said:
Fortunately, at dry ice temperatures the vapor pressure of ethanol is essentially zero so it is extremely difficult to ignite without a proper flame source, but once ignited it won't go out easily as the heat from combustion will produce the necessary gaseous ethanol to continue combustion. That being said, if your cooler of ethanol ever does catch on fire, just close the lid and it should go out long before it could melt through the cooler.
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Yeah - agreed. I was thinking mostly about storage and pouring it into and out of storage when warm...
 
Use a shallow metal pan that is longer than the blades being done. I use a "whole fish pan". They cost about $20 new.

Use the "denatured alcohol" from Home depot or any hardware store - $16 a gallon. You can use it over and over again. Pour it back into the can after the bath has warmed back up to room temp. Put the lid on loose and give it a shake the next morning to release dissolved CO2 gass. Them tighten the lid and set the can aside for the next use.

Put about 2 inches of alcohol in the pan and use about 3 pounds of dry ice (more is OK). Just smack the dry ice in the bag with a 2X4 or hammer to break it into smaller chunks. Add the DI slowly ... it will boil up, but that is normal. When the DI is all in the pan it is ready for the blades. It will stay cold enough doe the sub-zero treatment for at least 30 minutes.

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When I started I used Kerosene. Alcohol is much better. Kerosene tends to foam up and make a mess. You have to add the dry ice really slowly or it will bubble over. Once the bubbles slow down you know your liquid is cooled down.

Your slurry can get pretty firm after a bit. I tried a thermos idea just like you said. I was tapping a very thin filet knife into the slurry and next thing I know it was sticking out the side of the thermos. I have since got a Dewar for LN just for the convenience of having it on hand. Dry ice is a pain to get in Canada.
 
kdnolin said:
Not sure about a plastic container, it gets brittle in the cold. Denatured alcohol is what most makers are using with the dry ice
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Also don't ever seal the dry ice. The explosion is a lot bigger than you'd expect.
 
Just a heads up on Klean strip denatured alcohol. It’s not all ethanol. It’s about 50% ethanol and 50% methanol.

methanol can be dangerous to breath and get on your skin. We just discovered that klean strip was half methanol and we use it for all our blade cleaning and our refrigerated cryo bath.
 
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No denatured alcohol is all ethanol.

Most general purpose "denatured alcohol" is an ethanol/methanol mix. It is often sold as stove fuel, paint solvent/cleaner ( Klean-strip), or just labeled denatured alcohol in the paint department of a hardware store. As JT said, it can be as much as 50% methanol.

This is not the same as USP "denatured alcohol" often called methylated spirits. It is ethanol with 10% methanol or other methyl chemicals, along with something to make it taste terrible and smell funny (pyridine), and usually a blue/violet dye called "methyl violet". Around the turn of the 1900's they added 10% camphor. Then they switched to methanol. My grandmother was a young nurse when they started "denaturing" alcohol. The government taxed all ethanol. To avoid taxes on medical use ethanol, they denatured it. The hospitals used to have a little jar of 99% pure ethanol (200 proof) sitting by every bed with a mercury thermometer in it. The alcoholics (Grandma called them wino's) would sneak in to the wards and drink the contents of every thermometer jar. When they started using denatured alcohol, there were many cases of methanol poisoning and "Sterno blindness". To show that the alcohol was not drinkable, they added a purple dye to denatured alcohol and to Sterno, too. If you look at most of denatured alcohol in a clear glass jar you will see the blue tint.

BTW, in Europe and Australia, they banned methanol from denatured alcohol and use isopropyl alcohol and methyl ethyl ketone in its place.
 
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