I got a LN dewar!

The following isn't meant to diminish the value of a Dewar to knifemakers who make production blades, or the convenience to a maker in a very rural location. However, I have known of many folks who got one only to have it end up sitting out by the shop empty after a years use.

Lots of folks want a dewer ... but not all really need one.
You have $200 in your dewar (great price) and lets say $20 in the LN plus the gas for the trip to refill it. That lasts a month or so. You said you could grind up several knives in the next 20 days. Lets say you can pump out a steady 5 blades a month (that's 60 a year). The dry ice was costing you $6 to $8 a HT session. That means that the dewar and one refill does the same as about 30 dry ice treatments. Since we are figuring on 5 blades a month, that means it will take 7 or 8 months to break even (because you will have to refill the dewar three or four times). From that point on, the dewar is roughly the same cost as the dry ice ... but you have a couple hour round trip to make added to that. Unless the grocery store carrying dry ice is far away ( not likely to be more than ten minutes away in your area) you are economically better off with dry ice.
 
I will just put out there for a dewar with that small of an opening 10L@60D is not real great. My dewar is 2.15” opening I think and its rated 20L@222D. Dewars are rated in evaporation per day. Mine sits at .09L/D yours looks like is sitting around .17L/D. But once you remove the “I want one because it’s cool” factor you can look at it objectively. Stacy is right in that depending on the number of blades you do you could be spending more money. 6-10lbs of dryice will do a CRAP ton of blades. And to help it out you can put the blades in the freezer first to take a lot of the heat out first. We keep Liquid nitrogen on hand for any tricky alloy but use the freezer for most everything else. It is by far the cheapest and most consistent way we have found to treat blades. Now thy do come with a hefty entry fee but like a dewar you amortize that over the life of the unit and each blade. But stay away from any that are not working. I looked at the cost of refrigerant for mine and was shocked. The second stage uses a mix that’s about $2,500 for a small bottle.

This is what we use.
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Oh, I totally agree with all that dry ice works just fine. As I said in my last post, "not considering cost of dewar", then LN is less expensive for me. With this first dewar fill the LN cost me around 50¢ per blade (not counting cost of dewar) compared to $4 to $8 per blade for Dry Ice. Dry Ice is expensive because I very seldom do more than a couple of blades at a time. At the cost some places charge for LN I wouldn't even have considered LN, still be using dry ice.

"IF" I am looking at solely cost effective, then I should stop making knives since I sell very few knives. For me knife making is a cheap hobby - cheap compared to bass fishing or golf, and certainly cheaper than hanging out in bars {g}

Later
 
Making grapes explode would be worth the price of admission :D
 
You made a good choice Ken, ya don't gotta justify it to anyone.

The U. S Solid 10L Dewar is bomber.

Best "bang for the buck" Dewar

Last filled end of May, ran 6 blades (3 large ones) and 5 coupons

Still plenty LN left confirmed at the frost line on the dip stick today near end of July.

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Ken H> said:
Oh, I totally agree with all that dry ice works just fine. As I said in my last post, "not considering cost of dewar", then LN is less expensive for me. With this first dewar fill the LN cost me around 50¢ per blade (not counting cost of dewar) compared to $4 to $8 per blade for Dry Ice. Dry Ice is expensive because I very seldom do more than a couple of blades at a time. At the cost some places charge for LN I wouldn't even have considered LN, still be using dry ice.

"IF" I am looking at solely cost effective, then I should stop making knives since I sell very few knives. For me knife making is a cheap hobby - cheap compared to bass fishing or golf, and certainly cheaper than hanging out in bars {g}

Later
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Hmmm, not what the max length would be, around 14", perhaps 15" max with tang extending up in neck? I think the specs say internal height is 13.0" to bottom of neck. The 50mm neck opening it's also limited to around 1.95" or so. Several folks have commented on max width above.
 
Its harder to make ice cream with dry ice. Use a recipe with egg in it to have it turn out extra creamy.
 
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.
 
I'm several weeks ahead of ya.

Still going strong on this last fill

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Ken H> said:
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.
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How long is several weeks? What size is your dewar? I've got a 10 liter dewar, but understand a 20 or 30 liter dewar lasts LOTS longer. When I first got the dewar I was hoping to get 4 wks, but now I'm sorta hoping for 8 wks {g}

I don't mean to bore everybody with the number of posts on this dewar, I've always wondered how much time/liter would a dewar provide. While all dewars nor storage methods will be the same, I'm hoping my posts will give other folks an idea of time for a dewar.
 
Post #8
Ken H> said:
How long is several weeks? What size is your dewar? I've got a 10 liter dewar, but understand a 20 or 30 liter dewar lasts LOTS longer. When I first got the dewar I was hoping to get 4 wks, but now I'm sorta hoping for 8 wks {g}

I don't mean to bore everybody with the number of posts on this dewar, I've always wondered how much time/liter would a dewar provide. While all dewars nor storage methods will be the same, I'm hoping my posts will give other folks an idea of time for a dewar.
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DeadboxHero said:
Post #8
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Post #8 is by Natlek, post #27 you mention "The U. S Solid 10L Dewar is bomber", does that mean you've got the same U.S. Solid 10 liter I've got? Post #27 you also mention after around 8 wks you've still got plenty left. Hey, maybe I'll get over 8 wks. Now THAT would be amazing.
 
Dang it Ken, I meant 8 minus 3 for post 5 :D
We have the same dewar

We are twins now.
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Ken H> said:
Post #8 is by Natlek, post #27 you mention "The U. S Solid 10L Dewar is bomber", does that mean you've got the same U.S. Solid 10 liter I've got? Post #27 you also mention after around 8 wks you've still got plenty left. Hey, maybe I'll get over 8 wks. Now THAT would be amazing.
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Ken H> said:
with an unlimited number of blanks ready to go - LOTS of them. Considering each needs to sit at least 30 minutes (just a good round number, maybe less for thin blades) and perhaps hang 6 at a time (depending on size of blade), you could get a bunch of blades from one dewar.

$3.50/liter - that's what one place quoted around here. One place was about $5.50/liter, and another $4/liter. None could come close to the one that quoted 50¢ to $1.50 /liter depending on which time I called.

Just dip some LN with one of the straws and pour into the ice cream mix? I'll have to try that. My granddaughter is coming for a visit next weekend, need to have it figured out by then {g}
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I ask that with reason.If I make knifes for sale and they need LN i will make the math.....Then I will fill dewar and cut grind and HT that /number come from math/ 120 knives at once .If I have still LN in dewar after that it is gratis ...............make sence ?
 
Natlek, Makes perfect sense to me and I don't think you'll have any problem getting 150 to 200 blades by doing as you mention. Natlek, any idea what it will cost per liter to get LN in Macedonia?

Deadboxhero: Yep, it does sound like we're twins - both of us have the same 10 liter dewar. I won't get as long from my first fill as you're getting because I've played too much with LN, making ice cream, freezing grapes, etc.
 
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An update on my 10 liter dewar - it's empty. Sat (Aug 22) I checked and while it was still cold inside, there was no liquid LN inside. My sister was here and I tried to pour some LN into a container to freeze chunks of apple to break, and maybe make some ice cream. Nothing but vapor would pour out, no liquid. That was 9 wks. I think somewhere between 8 and 9 weeks the liquid went away, but it was still cold enough inside to treat a small blade. I think I can count on 8 weeks and I'm happy with that.
 
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