So today I decided to test the temp in my new oven. I read a post where I believe Stacy said that salt melts at 1475. I took a piece of steel and drilled a divot into it and places the salt in the divot. Heated my oven to 1440 and let it stabilize for an hour then put the salt in. I raised the temp by 5 degrees every 20 minutes till the salt melted. At 1480 it looked like it was trying to melt and at 1480 is did and pretty much disappeared. 10 degrees doesn't seem bad to me. Should I start changing my temps by the 10 degrees or keep testing or what?? Any help is appreciated! Thanks guys.
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Evenheat oven temp is slightly off....
- Thread starter NickBoyle
- Start date
Disclaimer: melting salt in your kiln may ruin your equipment!!!
Point one: pure salt is different from the salt we usually have, and the precise melting point vary accordingly to the degree of impurity.
point two: the melting point is not when the salt is already melted, but is measured precisely as the salt is just to beginning melting, which is difficult/impossible to catch by eye.
Kilns exibit more variation -than we like to believe- in temp. in different areas but where is our TC.
I hope it helps
Point one: pure salt is different from the salt we usually have, and the precise melting point vary accordingly to the degree of impurity.
point two: the melting point is not when the salt is already melted, but is measured precisely as the salt is just to beginning melting, which is difficult/impossible to catch by eye.
Kilns exibit more variation -than we like to believe- in temp. in different areas but where is our TC.
I hope it helps
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
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Lets look at it mathematically:
Your oven is running at 1500F it may be off 10 degrees. That is a 1:150 deviation, or .67% error.
Any accuracy less than 1% deviation is more than sufficient for our HT purposes. Most readouts and PID controls have a .5% accuracy.
The way to fine tune your HT is by keeping records and testing. Do HT at 10° brackets with coupons and test for results. Pick the best temperatures for your particular steel and your particular equipment.
To put this in prospective, We accept these statistical error rates as normal:
If you go to the doctor in the USA you have a 5% chance he/she will misdiagnose your problem
Depending on your tires and their air pressure, your speedometer is 5% to 10% off
If you are a USA married male between 20 and 24 years old, you have a 38% chance of getting divorced
If you are living in the USA, you have a .8% chance of dying this year
.... so a .67% error margin in your HT is pretty good.
Don't worry about a small amount of salt on a piece of steel in your oven. While crystalline salt ( rock salt) melts at 1474°F/801C, it won't vaporize until 2669°F/1465C
Just remove it when the test is done.
Your oven is running at 1500F it may be off 10 degrees. That is a 1:150 deviation, or .67% error.
Any accuracy less than 1% deviation is more than sufficient for our HT purposes. Most readouts and PID controls have a .5% accuracy.
The way to fine tune your HT is by keeping records and testing. Do HT at 10° brackets with coupons and test for results. Pick the best temperatures for your particular steel and your particular equipment.
To put this in prospective, We accept these statistical error rates as normal:
If you go to the doctor in the USA you have a 5% chance he/she will misdiagnose your problem
Depending on your tires and their air pressure, your speedometer is 5% to 10% off
If you are a USA married male between 20 and 24 years old, you have a 38% chance of getting divorced
If you are living in the USA, you have a .8% chance of dying this year
.... so a .67% error margin in your HT is pretty good.
Don't worry about a small amount of salt on a piece of steel in your oven. While crystalline salt ( rock salt) melts at 1474°F/801C, it won't vaporize until 2669°F/1465C
Just remove it when the test is done.
One thing you should consider, the temperature at the bottom of oven will be a bit different than temperature at the tip of TC also - just nature of ovens without fans. For a good check, put a couple of firebrick in oven so the salt will be right at the time of TC probe.
Looking at this link; http://www.omega.com/prodinfo/thermocouples.html Shows standard type K accuracy as being 0.75% which is around 11ºF at 1500ºF, so your 10ºF is within specs of a standard type K thermocouple. AND - that 0.75% is for a new TC with everything in perfect conditions. Accuracy of TC's do deteriorate over time.
Ken H>
Looking at this link; http://www.omega.com/prodinfo/thermocouples.html Shows standard type K accuracy as being 0.75% which is around 11ºF at 1500ºF, so your 10ºF is within specs of a standard type K thermocouple. AND - that 0.75% is for a new TC with everything in perfect conditions. Accuracy of TC's do deteriorate over time.
Ken H>
Re- disclaimer 
reaching the vaporizing of salt is not necessary to cause troubles, it does take a lot less to create an "unhealty" athmosphere within the kiln.
That's the reason why ht salt pots should be kept away from steel machinery and the like. My concerns regard the kantal elements and the tc itself, in theory, but i couldn't state the possible extents of this simple one time testing, just be careful
reaching the vaporizing of salt is not necessary to cause troubles, it does take a lot less to create an "unhealty" athmosphere within the kiln.
That's the reason why ht salt pots should be kept away from steel machinery and the like. My concerns regard the kantal elements and the tc itself, in theory, but i couldn't state the possible extents of this simple one time testing, just be careful
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
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Knifemaker / Craftsman / Service Provider
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- Aug 20, 2004
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I agree. Continued exposure to salts in environments where they can cause corrosion should be avoided. The exposure caused in a dry oven atmosphere for an hour or less should be minimal.
You are correct to give a caution disclaimer.
You are correct to give a caution disclaimer.