pottery kiln to heat treat?

K

kraut

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Apr 14, 2000
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Greetings ....Talked with a fellow to-day who has a pottery kiln for sale for $450. Cdn., it is top loading, 26" deep, has a digital control, 220 amp, and heats to well over 2000 degree's. I can not remember the make right now but it is not one I remember as making Knife furnaces.
This would appear on the surface to be ideal for heat treating my own blades, especially since a name brand knife oven would run me close to $2000.00 Cdn.
Can anybody give me any input pro or con as to its suitability and if positive how do I talk my wife into letting me get it.
Thanks Jim
 
Jim,
Kilns are great for heat treating knives. The top loading makes it easy to remove a blade for quench, just becareful when you open it, the gush of hot air can be harmful. What are the other dimensions besides depth? Make sure that you are not limiting yourseld to the length of blade you are going to put in, you can always kitty corner it in. Kilns are also made to take the high temps and are well insulated to hold in the heat. If you think about it,most potters have to fire a piece of pottery at 2000deg plus for at least a couple of days for it to glaze properly. It's also a great way to warm up the shop on a cold snowy day. As long as everything works go for it! Tell your wife to take up ceramics or pottery and you can both use it.
 
The knife ovens they sell are nothing more than small pottery kilns. You're in good shape, providing the kiln works properly. I would test the temp with some Orton Cones just to be sure that the controller is keeping the temp it says it is.

BTW, Striper, just to let you know, it would take between an hour and 12-14 hours to glaze fire the average pot depending on the techniques employed and the desired results. When I do a high fire for utilitarian ware such as mugs and bowls it takes about 12 hours to reach 2350 F. The only firings that take days are those of the wood fire people. And those firings, which would likely be more in the style of traditional Chinese ceramics, can take many days to accomplish. In that case they are usually firing hundreds or even thousands of pots in a multi chamber anagama or norigama hill climbing kiln. :)

Perhaps someone can shed some light on the proper techniques of heat treating in an electric kiln/knife oven??? I'm assuming some soak times.....
 
Has anyone ever converted one for salt pot usage? I'll get getting one similar to the one that is described, except for the digital control. I'm planning to cut a hole in the lid and insert the salt pot there and add a digital control.

Jamie
 
Talk to Howard Clark or Kevin Cashen on electicity and salt pots. Apparently 1500+ degree salt can be conductive as well as corrosive and it seems that the heating elements can do some interesting things in addition to self destructing and shocking the *crap* out of you...220 and a connection to the blade you are holding through the salt can lead to a tingly experience.

Salt pots work better in the gas forges although I use my low temperature salt in conjunction with electric heat and have had no problems.

All salts tend to be hygroscopic in nature...that is they will attract and absorb water from the air. When this happens and the salt is reheated it can overflow its container and end up in your kiln/oven. It will toast the elements immediatly and will be a mess to clean up. Left over salt will eat the firebrick when heated up again and will toast the new elements in short order. PITA and expensive if it gets away from you.

Brian
 
I bought a used pottery kiln for $80US.
and have been using it for the past year and a half with no problems. Mine is a side loader with crappy controls L M H. Since I do only Carbon steel in mine like 5160 there is no soak time to speak of.

One thing for sure is check the temp and be sure the gauge is accurate!!!
Digital gauges are the way to go if you can afford them.
Also, like they said be sure it is deep enough.

A word of Caution when doing Oil quench steels, I use a volunteer (Usually by bribery) to open and close the door. It's a REAL adventure to have a 1500deg piece of steel slipping out of your tongs as you are trying to wrestle the door shut and get the blade into the quench before you loose Temp...

Use common sence, face mask, hat, respirator, a 14-16" pair of tongs and welding gloves.

If your doing Stainless get an inert gas set up, not expensive and worth every penny! Paul Bos is a great contact for some advice here.

A Salt pot will ruin your elements in very short order, be sure you learn how to replace them yourself if you use this.
 
Whats it cost to fire a pottery kilm up for heat treating, I had 1 I could get for a little of nothing but was told that the expense to heat it up would eat me a live in electric, unless I was going to keep it fired for long peroids, then it would use a lot of juice when not needed. I said to heck with that. Is this true or was that a bunch of bull ?

Bill
 
What I was thinking of doing didn't involve the inside of the kiln seeing anything with the salt. I was thinking of cutting a hole in the top of the kiln and have a sealed container sitting on the bottom of the kiln with the top outside of the top of the kiln. I've replaced elements before, I know how to do that. I've heard of people doing this, some comment about the tingliness and others make no reference. I remember in one of the knife rags a while ago Tim Zowada had pictures of kilns converted to salt pot heaters. Is there a way to minimize this experience?

Jamie
 
Problem is when hydrated salts overflow when heated and go around messing everything up.
You could weld a large iron sheet flange to the salt pot mouth so that any spilled salts overflow OUT of the oven top, not going inside, but I don't know how much such a trapping could work.
Anyway, listening to what a lot of experts say, electric ovens are the best way to go for heat treating, but they are also the most expensive to run.
 
Here's a good way to lower the cost of heating an electric pottery kiln and being able to use salt with no worries: Get a free used kiln with burned out elements. Cut a hole in the top of the kiln about 6 inches in diameter. Cut a similar size hole in side of the kiln near the bottom. Stick a weed burner wand attached to a propane tank in the hole for your heat source. Voila, instant gas kiln, very much like a larger version of Wayne Goddard's one brick forge.

I have built kilns like this for Japanese Raku firing and they work great. The salt will still eat the fire brick but at least you don't have to worry about the elements. If you want to make it salt resistant, there is a refractory product out there called ITC100 that you can spray inside the kiln that will significantly reduce the damage. To facilitate easy removal of the objects inside I remove the door hinges of the top loading kiln and screw an extra handle on so that I can simply lift the top away and set it off to the side when ready to pull.
 
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