LN dewar

KenH

Well-Known Member
I have thought about using Liquid Nitrogen before for heat treating knife blades? Dry Ice slurry works just fine, but at $6 to $8 each time it gets expensive and a bit of hassle getting the stuff each time. I've always wanted LN, but never considered it due to cost. The dewars were in the $400 range (and still are for a 20 liter size), but a company put a 10 liter on sale for $200 shipped (ebay added $15 tax)

I called around about price to fill the 10 liter dewar. Prices ranged from $15 over in Mobile, to $62 locally in Robertsdale. I called 5 different places, the other 3 places were $40 to $45 to fill. Big spread in price.

I like the U.S. Solid dewar better than the other Chinese made dewars. Per this site https://ussolid.com/about-us/ the website almost seems to sound like "made in USA", but it doesn't say that exactly. Note the "make our own" and "established our own manufacturing" which could sound like "Made in USA", but could well mean they are still made in China, but under U.S. Solid's specs and supervision which would give a chance to be better than the usual "lowest bidder" from China. "In our own research (Spectroelectrochemistry, Femtosecond-laser spectroscopy, Photochemistry and Biophysics) we’ve encountered a series of overly expensive equipment that haven’t satisfied the demands put up to by modern research. We decided to make our own. After some careful analysis we’ve established our own manufacturing and are rapidly becoming viable competition in the North American market."

Anyway, the dewar got here yesterday, I went to fill it this morning. A 2 hr round trip, about 60 miles total. I went to the $15 fill place. I called to double check price, filling, etc. This morning on the phone the salesman told me $8 to fill the 10 liter dewar. Hmmm, that's almost too good to be true. I drove over, when I walked in he says "Sorry, I gave you the wrong price on the phone....... it's $5.50 including tax!" Wow I thinks. I paid the $5.50, took my dewar around back and they filled it. I'm now back home.

Now to see how long the dewar lasts with me playing, freezing grapes to watch them break like glass. AND see how many knife blades I can get treated with that dewar before it runs dry. If you've never played with LN you need to come over and freeze some stuff {g} Throw the frozen grapes on sidewalk and they shatter like glass. The website says the 10 liter will hold LN for 60 days when it's not used. I'm hoping under normal use to get 30 days. I'm thinking I can profile up several blades during the next 20 days or so, then have them HT'd ready for bevels and finishing at my leisure. Anybody care to comment on expected holding time with the 10 liter dewar?

Ken H>
 

EdCaffreyMS

"The Montana Bladesmith"
Based on my experinces (my Dewar is a 56lb capacity/a tad over 25 litres)...... terrible pricey to fill around here, and in the beginning was lasting me about 2 weeks MAX. Then I had a brain shower (my brain ain't tight enough for a "storm) :) But, what I did was build a plywood box, with a hinged lid. Inside as 2" bigger than the diameter of dewar, and lined the ENTIRE (including the lid) with 2" thick foil backed foam insulation. I place the dewar in the box, and fill ALL the airspace with vermiculite, and top it off with a piece of R30 fiberglass insulation covering the top of the dewar..... With normal use, the LN will last for 35-40 days..... basically doubling how long it lasts versus the dewar alone. I'll get you some pics over the weekend and post them here.
 

KenH

Well-Known Member
Thanks for comment Ed, your 2 weeks was about what I was expecting myself. That's why I'd never really considered LN, due to cost. At $5.50 to fill the 10 liter dewar - price isn't so bad. I don't expect to keep getting that price - the ticket says "bulk pricing" and a 10 liter dewar certainly is not bulk sales. I've got the dewar in the shipping box it came in. A heavy pasteboard with about an inch (tad more?) of mostly air bubble wrap all the way around dewar, both bottom and top. I'm thinking that might help some. Your idea seems better. I'll store in an AC'd room so it won't have to deal with heat of summer, and around here on Gulf Coast of Alabama that's pretty hot.
 

KenH

Well-Known Member
Like all the other dewars of any size the specs say 50mm (1.9685"). My dewar seems a tad tighter than that, I can slide a 49mm (1.93" - maybe 1.94"?) blade that's about .100" thick thru the neck. One guy has said he can get a 1.95" blade in his 10 liter dewar of the same brand. Maybe a really thin blade would do that.
 

Gene Kimmi

KNIFE MAKER
I bought a 10L from amazon that had been returned. I think I payed around $235 for it. I have been super impressed with how well it holds.

I filled it on March 26th and didn’t use it until mid May. I heat treated 27 or 28 blades and by the end of May, there was still a little left in it.

Around here, it costs me $50 - $55 dollars to have it filled.
 

KenH

Well-Known Member
That's two months - pretty good. I'm well aware of how good a price 50¢ is. I don't really expect to keep getting that price, but if it will stay at $1.50/ liter I won't complain.
 

Smallshop

KNIFE MAKER
I borrow a neighbors semen tank dewar...when he's not draining bulls he lets me use it...$72 to fill...

I think Ed has the right idea to get more mileage...
 

Smallshop

KNIFE MAKER
I think it is a 10 litre...I don't have it here right now...The mouth was just a bit over 2"...

You can buy them with larger mouths...which is what I want. so I can bolt knives together to maintain straightness in HT.
 

KenH

Well-Known Member
Ted, any idea how long your normally get from a fill on the 10 liter dewar?

The 1.94" mouth ID is a concern for me also. I've always clamped AEB-L blades between aluminum bars during dry ice/deep freeze treatment to keep straight. Not sure how this is going to work. I've got some 1/4"X1.5" aluminum bar I'm thinking of trying to see how that works. Even on the 1.95" wide chef knife blades there would be only 3/16" or so hanging outside the bar. Any blade that's 1.95" wide will be .090" or more thick so maybe that will work? All my AEB-L blades are profiled only during HT.
 

Smallshop

KNIFE MAKER
About 6 weeks...Last year I found a "big mouth" on amazon for about $350...maybe search it if that's in budget...My knives are 1.5 tall i'm hoping to get 4-5 at a time in...i leave 'em in for 6hrs.

you could prolly draw the blades and bar and opening in CAD to check.
 

KenH

Well-Known Member
Well, since I've already got the 10 liter dewar now another dewar for $350 isn't in the budget {g}. 6 wks? That's pretty good.

I used the LN yesterday on a 9" chef (1.93" wide) and a small folder blade. I only left in an hour but still seems to have raised the Rc between 2 and 3 points. The chef blade came off the quench plates with a pretty good bow, but since AEB-L is like a wet noodle right off the quench plates I was able to straighten pretty easy before hanging in LN. Came out of LN an hour later with a slight bow, clamped between aluminum bars for tempering. Came of of tempering oven straight. This morning when I put on SGA it just "kissed" blade all the way down and after cleaning up both sides it lays flat on a granite plate.

Looking forward to HT'ing a couple more blades over the next couple of days.

Later
 

Smallshop

KNIFE MAKER
Well, since I've already got the 10 liter dewar now another dewar for $350 isn't in the budget {g}. 6 wks? That's pretty good.

I used the LN yesterday on a 9" chef (1.93" wide) and a small folder blade. I only left in an hour but still seems to have raised the Rc between 2 and 3 points. The chef blade came off the quench plates with a pretty good bow, but since AEB-L is like a wet noodle right off the quench plates I was able to straighten pretty easy before hanging in LN. Came out of LN an hour later with a slight bow, clamped between aluminum bars for tempering. Came of of tempering oven straight. This morning when I put on SGA it just "kissed" blade all the way down and after cleaning up both sides it lays flat on a granite plate.

Looking forward to HT'ing a couple more blades over the next couple of days.

Later
Excellent ! The A-2 has been very stable on warpage...I just want through put to be a bit better. I do plan on running some AEB-L so hearing it is manageable is good!
 

J. Hoffman

Dealer - Purveyor
I have a 47l with a 4" opening. It keeps for about 10 weeks. I usually have several blades ready for heat before I fill it. Also, just so you know, the blades don't need to be submerged to get the efect.
 

KenH

Well-Known Member
Time for an update on the 10 liter dewar and LN holding. Today is a couple days over 5 wks and there still seems to be about 3 to 4" of LN in bottom of dewar. I checked this by putting a straw (ya'll know the SS "straws" that are used with dewar for semen storage) and it seems to frost up around mid point. This is only dipping straw into dewar for a few seconds. Left in longer I'm sure it would have frosted up all the straw. I "think" I could still treat a blade with the amount of LN in dewar. BUT - I'm happy with the 5 weeks, remember I played with the LN some, making ice cream, freezing grapes, etc. I'm sure I used well over a liter just playing.

The dewar is stored in the pasteboard shipping box that has a thin layer of bubble wrap around dewar which I'm sure helps a very small bit with storage. The dewar is stored in the A/C'd radio room that's kept around 74°F during day, and around 80°F or so at night. Let's see how much I have to pay this time to get it filled. Hard to imagine I can get the same $5.50 fill cost.
 
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KenH

Well-Known Member
For another update on dewar holding time of LN. I filled 10 liter dewar June 19th. Today, Aug 4th I checked again and it's still holding. No reason it won't be good this Friday Aug 7th for 7 weeks of holding. I'm treating more blades today and temperature about mid level is still -278°F so I think it's good.

I'm really AMAZED how well the dewar is holding.
 

bladegrinder

Well-Known Member
The dewar is stored in the A/C'd radio room that's kept around 74°F during day, and around 80°F or so at night.
If that's a small room your keeping it in Ken, watch going in there because as that liquid nitrogen evaporates it'll displace the oxygen in that room.
watch you don't fall out going in there.
 

KenH

Well-Known Member
I appreciate the concern, but the storage room is about 22'X45' and has decent circulation - it has central heat 'n air, and doors to outside are open from time to time. You're right, if too much N2 is released into the air it can be a real bummer!
 
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