Building a propane torch kiln out of salt

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kimjune01

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Apr 25, 2007
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I saw a block of salt at a wholesale store the other day and thought about substituting it for the firebrick(as in the $50 knifeshop). I know that firebricks are not so expensive but I recently moved to a smaller town and was wondering whether or not salt(it's really dense and feels like a brick, about 1 cubic ft.) is a viable option. Thanks
 
I think the salt would combust. You can order firebricks or ceramic blanket from Darren Ellis fairly cheaply. You might be able to try something with perlite and kitty litter?

Edit: Sorry, the salt won't combust, it will melt though. Around 1400 degrees it seems, a little too cool for knifemaking.
 
Sodium Chloride doesn't burn. That said, the melting point is 1474F. Not a good idea.
 
Caught my mistake before you could post it Mike :P We were just discussing this in the office and I'm trying to figure out what it was I saw burning on that bunsen burner in Jr. High...
 
You remember the glare off sodium ions most likely, a brilliant red. The same basic thing going on with a sodium vapor lamp. The sodium chloride isn't burning, though.
 
Thanks, Howie! :D I should have known I was wrong when I asked myself, "Potassium must be yellow, then. Right, Mike?" :rolleyes: Been too long since I did flame tests, obviously. I should'a just shut up about the color, eh? :)

Maybe I was thinking of calcium. We used some flame testing in regenerating ion exchange columns once upon a time. Wiki has a good table: http://en.wikipedia.org/wiki/Flame_test
 
Thats a good idea! I guess it could be a safegaurd to make sure you don't overheat the steel, or maybe when the salt melts, pull out the blade and by the time you reach the quenchant tank, it's cooled down to 1450, or whatever the optimal temperature is for 1095.
 
1474F is the temp at which extremely pure sodium chloride melts. Any impurities cause a phenomenon called melting point depression, and the salt will melt at a lower temp. Common iodized table salt is one example; it's spiked with potassium iodide to provide iodine in our diets. The melting point would be lower. This phenomenon can be easily understood by considering the melting/ freezing points of salt water, which is much lower than fresh water. Same basic result.

Using sodium chloride as a temp indicator under anything but lab conditions is probably not a good idea, IMO, though it was good creative thinking. Tempilsticks and tempil powders address these needs with some limitations.
 
Table salt also has Silicon Dioxide on it to keep it from absorbing water...
You know the Morton's saying "when it rains, it pours"?
Yes, they do coat it with glass...:eek:
and they do the same with Chili powder...
Potassium flame is violet, Mike. :D
Look up some threads on salt pot heat-treating...
There are a lot of salts besides NaCl. Some that are liquid at much lower temperatures.
 
Very nice lateral thinking dragon. Now there are many different salts which melt at varying temps... Why dont you commercialise the idea and make salt cubes of varying constituents that melt at specific temps so one could buy a cube rated for your requirements?

Interesting thread

Lang
 
Well they already do make pyrometric cones for pottery, I assume they have a simmilar product for steel.
 
I saw some special crayon-esque sticks somewhere one time that were supposed to melt at certain temps. I kinda figured that table salt wouldn't work like pure sodium chloride.
 
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