Element Life and Kiln Best Practices

[Crooked Lawyer Potter]

I fire my electric kiln (a Skutt 822-3) to cones 06 and 6.  My last set of elements lasted only about 100 firings, even though I did a "break-in" firing with an empty kiln as suggested when they were replaced.  I suspect that I have "bad habits" that shorten the elements life-span.  For instance, I lack patience and often remove plugs at <1000 and open the lid at <500 F.  Is that bad?  I also "candle" a lot, using the kiln to hurry along not quite dry pieces, often pre-heating for anywhere from 2 to 12 hours before beginning the firing.  

Anyone have a take on what to do -- and not do -- in order to extend the lives of elements?

[dhPotter]

This may have been on this forum. It is very helpful.

When to Open the Kiln

1. When the kiln temperature falls to 600°F, open all the peep holes.

2. When the temperature reaches 450°F prop the lid 1 inch.

3. When the temperature reaches 350°F, the lid/door can be opened 3 or 4 inches.

4. When the temperature reaches 250°F you may completely open the kiln allowing it to finish cooling prior to unloading.

5. When the temperature hovers around 200°F the kiln can be unloaded.

[PotterPutter]

It sounds like you already know that opening your kill while it’s too hot as well as candleing  for a very long time are both contributing  your elements wearing out.
 

Is your kiln vented? If not, do you prop the lid until it reaches 900° and leave the top plug out during the entire firing? Do you regularly vacuum your elements? All of this will help you get the maximum life out of elements.
 

I have a Skutt 818-30A and also fire to Cones 06 and 6. I have about 175 firings on my elements and they still work fine. My bisque-to-glaze firings are about 2/1 and I only candle bisque firings for 1-2 hours. I don’t candle glazes firings. 

[Roberta12]

@Crooked Lawyer PotterMy kiln repair person said that firing clay with iron or manganese  in it can shorten the life of your elements.  Has anyone else ever heard that?

I seem to have a short life on my elements as well.  

[Pyewackette]

I'm pretty sure the vast majority of clay has iron in it, even our studio "white" stoneware has enough iron that it turns pink in bisque.  Maybe porcelain is iron free. 

Now I feel like I have to find a youtube video of someone vacuuming their elements ...

[Pyewackette]

So I did find this in one of the manuals for the kiln controller:

Quote

avoid firing clay with high sulfur content. The sulfur erodes the thermocouple making it brittle and easy to break.

If sulfur erodes the thermocouple, I would imagine its not great for the elements either?

[Min]

Temperature is a main factor in how long seasoned elements last for. Chart below showing proportional length for different temps. I have a 20+ year old kiln I use only for bisque, the elements are the original ones and it's still firing okay, not like new but not horrible either.  Holding at low temperatures will wear out relays faster but will have a negligible effect on elements. Holding at high temperatures will shorten element life. AMP kiln elements are a good choice if you fire and hold and higher temps, like for crystalline firings.

Chart is from Kanthal, note that degrees C and F are reversed. 

Fumes from clay and glazes are also going to play a part on element longevity. Extreme example of this is if you try and do a reduction firing in an electric kiln, elements will degrade really quickly. Not venting the kiln will reduce element life.

[neilestrick]

Temperature is the biggest factor. Your elements will last a lot longer firing to cone 2 than they will firing to cone 6. I fired to cone 8 for a while, and switching to cone 6 extended my element life at least 25%.

What type of clay you're using will also affect element life. 'Dirty' clays that have a lot of stuff (carbon, sulfur) burning out will corrode elements faster. Using a downdraft vent will increase element life, and will greatly reduce the corrosion of the metal parts of your kiln.

Rapid cooling probably doesn't help.

Firing schedules can also affect element longevity. Long holds at high temps are pretty hard on them, however holding to gain heat work is less detrimental than firing hotter to obtain the same heat work.

I've got a customer who has very poor element life compared to my other customers, and we really don't know why. We've done everything possible to make them last longer, with some success, but not enough to get them up to where they should be. I've often wondered if the electrical service itself could be a factor.