Heck of a deal on a 10L dewar

Shucks, just checked and the price has increased to $245 shipped. Still a good deal, but not like the $212 I saw yesterday.
 
How large? Good question and depends on several things. How far do you have to drive for a refill? Cost of refill? Do they charge a flat rate/liter for LN? OR, does a larger container cheaper/liter?

As Gene says the 10 liter will hold around 6 to 8 weeks or so, depending on how many times it's used. You might wish to check around for prices before ordering. Prices in my area run from 50¢/liter to $6.50/liter for a 10 liter dewar depending on which welding supply I check.
 
Blades have to be smaller than 50mm wide. Thats the problem with a lot of Dewars if you want to do kitchen knives. There is a wide mouth 5 inch 20L on Ebay, but it is like $469. The name brand ones like the Taylor Whartons are up in the $700 range now and that may be for a used one.
 
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jmforge said:
Blades have to be smaller than 50mm wide. Thats the problem with a lot of Dewars if you want to do kitchen knives. There is a wide mouth 5 inch 20L on Ebay, but it is like $469. The name brand ones like the Taylor Whartons are up in the $700 range now and that may be for a used one.
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Thanks for that tidbit! I do want to do kitchen knives!
 
jmforge said:
Blades have to be smaller than 50mm wide. Thats the problem with a lot of Dewars if you want to do kitchen knives. There is a wide mouth 5 inch 20L on Ebay, but it is like $469. The name brand ones like the Taylor Whartons are up in the $700 range now and that may be for a used one.
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Can you link the 20l wide mouth for $469? I only see a 10l wide mouth for $469 on eBay.
 
Realize a wide mouth holds LN a shorter time than does a 50mm mouth. See this spec on a widemouth - only 30 days holding time.
https://www.amazon.com/dp/B06ZZS9BD8/ This one shows only a 25 day holding time https://www.amazon.com/dp/B00KO8OXQA

That is compared to a 50mm mouth spec's at 100 days holding time. Just something to think about. Of course it depends on how many blades/yr you make that are over 1.97" wide at widest point.
 
KenH said:
Realize a wide mouth holds LN a shorter time than does a 50mm mouth. See this spec on a widemouth - only 30 days holding time.
https://www.amazon.com/dp/B06ZZS9BD8/ This one shows only a 25 day holding time https://www.amazon.com/dp/B00KO8OXQA

That is compared to a 50mm mouth spec's at 100 days holding time. Just something to think about. Of course it depends on how many blades/yr you make that are over 1.97" wide at widest point.
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Three of the eight blades I made on Saturday are right at 2" I also make some cleavers that are 4". I hate to lose the Ln2 that fast, but I don't think that small mouth is going to work for me.

I already ordered one from Amazon. I can return it if it doesn't work out for me.
 
One thing to remember is the LN doesn't have to stay in the Dewar. It can be poured with proper caution into another container more suitable. For instance, a PVC affair like is made for ferric chloride etching could be insulated with heavy rubber foam or one could wrap a 1 liter graduated cylinder. The transition from austenite is pretty quick. An hour or two at cryo temp is sufficient and one can then return remaining LN to the Dewar. Face shield and heavy gloves and caution and there shouldn't be any problems.

I say this knowing I may be making light of something that scares a lot of folks. I used LN in the lab for many years and am used to it. You can, too, just be careful. Hell, when the dermatologist went to freeze a skin flap on me, she left and returned with the LN in a paper coffee cup!
 
We got a sst bucket at work that's big enough to hold a couple real big bearings we use. We just have the gas guy come by and dispense it right in the bucket. Buncha rednecks kickin it around half a day then fishing a bearing out of it...no casualties yet.
 
I probably shouldn't mention you can actually stick your finger in the stuff if you pull it back out immediately. :D

When I was somewhere around 10 or 12 (early '60s), school took us down to the Museum of Science and Industry in Chicago. What a marvelous visit for a kid from a small town. They used to do science demos right out in the middle of a big hall so folks could gather around. On the day we were there, the demo was the wonder of liquid Nitrogen. The fellow doing the demo did the usual: froze a rose and crushed it, made a hammer out of a banana and drove a nail, and another out of a paper cup, popsicle stick, and mercury.
Then, he stuck his finger in the stuff and pulled it back out, explaining that the LN boiled so fast because of the heat in the finger that it caused a gaseous nitrogen blanket around the finger that slowed heat transfer. Then he asked for a volunteer. That kid did it hesitantly, then did it a second time, and soon all of us were crowded around trying it.

Imagine doing that nowadays. Hammering without everyone having safety glasses and a big plastic shield! Mercury! Having kids stick their fingers in LN! How did we ever make it through childhood?
 
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