Dry ice bath tub

bladegrinder

Well-Known Member
So after more than once of having my dry ice-acetone bath turn into one of the most inefficient messy operations I've had to do,
I came up with an idea here. I think it's a large idea but haven't used it yet. in theory it's a lot better than how I've done it in the past.

So I built a simple wood frame box with a piece of foan insulating board glued to the bottom.


Put in a large bread loaf pan I got off Amazon, 16" x 4" x 4" and grease it up real good with vasaline.


Sprayed in a can and a half of expanding foam........


Added a brace to keep the foam from crushing the bath tub.....


Let it cure over night......


And Wa-La......Dry ice- Acetone insulated bath tub ! :D

 

Self Made Knives

Well-Known Member
I did almost exactly the same. I also found out the the first time I tried pouring acetone into the loaf pan out of a 1 gal metal can how quickly foam disappears. Just had a little gurgle and chug and dripped some on the end foam. Wiped out a 3 inch square area of foam! I even had aluminum tape on the edges, but it still found it's way in. Be careful.
 

BossDog

KnifeDogs.com & USAknifemaker.com Owner
Staff member
First, I think that container is a great idea.
Sam the safety guy here: Acetone is toxic. I suggest using RV anti-freeze. It's cheaper than acetone. It won't evaporate away. It is pet and human non-toxic and is not flammable. It will congeal in dry ice but it will "melt" as the dry ice is exhausted.
 

bladegrinder

Well-Known Member
Thanks guy's, Ken I don't know how how long the dry ice will last in this new container but it's got to last longer than how I was doing it...in a plain old un insulated metal pan out doors here in Fl. I'm looking forward to trying it, I'm sure I'll see a significant difference.

Joe, I knew ahead of time the acetone would act like an acid to the foam, I planned on filling it by pouring it in using a glass, for emptying it out the pan has ears so it can be lifted out. that's why I used vasaline on it, for a release from the curing foam.

Tracy, now that you mention it my first run with this will be with what you suggest, RV anti freeze. I'm not really concerned with the safety aspect of using acetone but the first time I did this procedure I used kerosene. I didn't measure the temp. but it got thick like your describing of RV antifreeze...I liked that because the blades stood vertical in the bath, with acetone they just end up where ever and tend to move around on their own. I kind of think that may lead to warping, I don't know but I didn't like it. I did get a measured temp. of -104 F with the acetone, I can't say how accurate it was but I think it was reasonably accurate. I'll take a reading and post the results when I use the RV juice.

But I'm never using kerosene again because it was a stinking mess from the get go.
 

C. Killgore

Well-Known Member
I kind of think that may lead to warping, I don't know but I didn't like it.
I'd agree with that! I did a number of blades out of AEB-L years ago and used the dry ice / acetone bath. I had a lot of warping issues in that dry ice. I had to start being super careful and hold them upright to make sure they didn't fall over. It seemed to work better after that but was a pain. That was my theory anyway.
 

KenH

Well-Known Member
What's the attraction of RV antifreeze? Is it better (gets colder?) than denatured alcohol? Less expensive? I've never used anything but denatured alcohol and it hits the magic -95°F fairly easy.

Yes, AEB-L LOVES to warp in dry ice. I've got to the point of clamping blades between a couple of aluminum plates while in mixture and no longer have any problems with warp. I've even clamped 3 or 4 blades stacked on top of each other between the same plates with no problem.
 

MarcWeitz

Active Member
Why mess with dry ice, acetone, antifreeze (deadly to dogs if ingested) and not just use LN2? Is it availability, cost per use?
 

bladegrinder

Well-Known Member
Ken, I use plates with longer blades, shorter blades seem to survive without warping.
I know some use alcohol, acetone,antifreeze and kerosene. I just want to try the antifreeze and see how it goes.
The kerosene is over for me.

Marc, the only reason I don't use LN2 right now is I can't justify the expense of a dewar and having it filled for the number of knives I heat treat at this time that require a freeze. AEBL only requires -100 which dry ice and a carrier can achieve.
 

Smallshop

KNIFE MAKER
I went to LN2 when I discovered that my rancher friend only needs his bull sperm harvesting dewar a few weeks each year....Lol!

Before that I tried Tracy's method and thought it was easy and worked well. RV antifreeze is pretty cheap...But either way I have to drive 100+ miles for dry ice or liquid nitrogen...a dewar a little bigger than a small propane tank costs about $75. And would last me about 4 weeks.
 

BossDog

KnifeDogs.com & USAknifemaker.com Owner
Staff member
Locally we pay anywhere from $45 to $65 to fill a 30 liter dewar. In reality the dewar will fill to around 20-25 liters as it will boil over otherwise. The price is different every time we refill from the same place. It is such a fringe item the counter guy really just guesses at the price. I talked to someone the other week that said LN was $30 per liter locally but could find dry ice for a few bucks a pound. His choice was easy, he uses dry ice.

Regular anti-freeze is toxic and attractive to dogs or cats and should not be left out. RV anti-freeze is non-toxic to humans or animals (check the label of course, I haven't seen every brand).
 

KenH

Well-Known Member
Regular antifreeze is toxic and attractive to dogs or cats and should not be left out. RV anti-freeze is non-toxic to humans or animals (check the label of course, I haven't seen every brand).
I repeat my question, how does RV antifreeze compare to denatured alcohol for low temp? Denatured alcohol will achieve around -90F to -95F. I think acetone might get a tad lower, seems I've read -104F. Is RV antifreeze easier to handle? Last longer than alcohol with dry ice?

I read RV Anti-freeze comes in two ratings, a -50F and a -100F. That seems to be what's called the "burst point". I've not been able to find a spec on where it freezes solid. Freezing slushy would be ok for dry ice, but not if it froze solid. Looking at this: https://www.amazon.com/dp/B07MBQ5YX3/? that's rated at -50F, is that what congeals with dry ice? OR, does that require the -100F rated stuff?

Ken H>
 

bladegrinder

Well-Known Member
Freezing slushy would be ok for dry ice, but not if it froze solid
I have no idea how any kind of anti freeze would react with dry ice, but slushy to me is good.
When I used kerosene it was like a 7-11 slurpee and the knives slid right in standing up, I've only used acetone other than that. does alcohol thicken ?
as for safety, that's no worry for me. I don't have animals or children and with all the nasty jars, jugs and bottles of stuff I have laying around my shop anti freeze doesn't set off any alarms for me.
 
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