oxidizing new elements to cone 9?

[vyse]

Hi! This may be a silly question!

I have bought a used electric kiln. It is not in pristine condition, but it seemed good enough and the size seemed to fit my needs with some room for growth.

I have consulted a local kiln technician - a man about a 100 years old, well trusted, and ended up replacing only one element which was cracked, since the rest was still in okay state. He was really lovely when connecting the kiln, but I think my million anxious questions have put him off somewhat, and I would like to avoid bothering him again...

I would like to test the kiln now - it should fire to stoneware temperatures, but I would like to check it with pyrometric cones to make sure that it is showing the correct temperature and to see if everything works.

I also need to oxidize the new element. 

I have read that oxidizing and test firing a new kiln should be done anywhere between a fast fire to cone 04 to a slow fire to cone 5. The range is quite wide and has left me somewhat confused.

My question is: can I roll my test fire to cone 9 and oxidizing the element into one firing? Or will it somehow damage the new element? I also got some new kiln furniture: do they also need to be fired first with the kiln empty?

I am very new to firing, since I used to use a studio that fired for me, and I still have a lot to learn!

 

 

[Bill Kielb]

Electric kilns.

Don’t go to cone nine! The higher the temperature, the shorter the element lifespan. Most folks go to some temperature above about 1830 degrees so a medium speed bisque to 04 is common. https://skutt.com/images/Top-5-ways-to-Extend-the-Life-of-your-Kiln-Elements.pdf

With respect to elements, I always change the whole set because they wear equally for the most part unless one of them has shorted and the others are still fairly new. . A cone ten kiln will fire cone six stuff on the order of 100 - 150 firings before they wear enough so they won’t make temperature. A cone 8 ratę kiln  fired to cone 6 work likely gets 50 to 75 firings before they are worn excessively.

A cone 10 kiln fired to cone 10 likely only gets 25 - 50 firings so temperature has a very dramatic effect on element life so no cone 9.

[Min]

3 hours ago, vyse said:

can I roll my test fire to cone 9 and oxidizing the element into one firing? Or will it somehow damage the new element?

I wouldn't do this. To get a good layer of oxidation on the element wire you want to fire the kiln without pots in it. Don't need to do a conditioning firing for the furniture.

Euclids  recommendations for conditioning the elements is:

"Pre-oxidizing the elements is recommended for customers using their kilns at elevated temperatures (cone 6 and higher), or under corrosive or reducing conditions. To oxidize the elements, heat your empty kiln to a temperature above 1922F/1050C with the peep holes open and the lid raised slightly. Holding the temperature there for 6-8 hours will ensure thorough oxidation of the elements, but most of the oxide growth occurs in the first 1-2 hours. This procedure grows a protective oxide coating on the elements before the elements are exposed to any harmful atmospheric conditions. This procedure is usually only done once, but can be repeated as required if the kiln is fired under harsh conditions such as a reducing atmosphere (which actually removes the protective coating)."

Regarding what Bill said about cone 9 being hard on the kiln and elements, chart below showing relative number of firings at different temperatures. (the degrees C and F are reversed in the chart) Info chart from Kanthal. You can see the firings for midrange is about double compared to highfire.

Do you have cone 6 claybodies available to you in Denmark or is it just lowfire and highfire clay there?

Welcome to the forum.

[Piedmont Pottery]

On 7/7/2021 at 4:59 PM, Min said:

Don't need to do a conditioning firing for the furniture.

Generally correct, but nitride bonded silicon carbide shelves from some manufacturers do need to be fired once to burn off some chemicals that can produce discoloration on pots.  I don't know if this is true for all manufacturers of nitride-bonded SiC shelves or not, but I ruined a load of pots by not pre-firing new shelves.

[vyse]

Thank you all for the answers and warm welcome! My main reason for pushing to cone 9/10 was to see if the kiln can handle it - it should theoretically since it is rated to cone 10,  but since it is a pretty old, used one I wanted to double check. I want to know if I can get myself overly excited about trying crystalline glazes:)  I know the previous owner regularly fired to cone 7.

 

But I followed your advice for now and I am waiting for it to cool down after empty firing to cone 05.