Cone 10 Glaze Firing Schedule for an Electric Kiln

[ArborRoadPottery]

Hey yall!

I recently was given a kiln, the Cress E-23. I have never fired my own work prior to this time, opting to drop it off at a studio because I did not have the wiring for a personal kiln. 

I ran a successful bisque fire for the first time, and am wanting to do a glaze test this week. What is a good schedule for a cone 10 firing? Is it important to cool slowly? What knowledge can you share?

The schedules I have found (though scarce) are like this 

SEG1 100/hr to 220  with a 1 hour hold

SEG2 300/hr to 2300 with no hold 

SEG3 108/hr to 2361 with a 1 hour hold

[neilestrick]

That should work, assuming it can keep up with 300/hr at the high temp. Also, check what the high temp limit is for your controller. There's nothing wrong with using the pre-programmed medium speed schedule.

Any reason you're firing to cone 10? If the studio that was firing your work was doing it in a gas kiln, it won't look the same in the electric.

[Bill Kielb]

The E series are electronic and have an electronic controller, Bartlett I believe. There should be examples in the manual as well as the Bartlett controller manual.  Both are downloadable online. Cone 10 will be tough on this kiln and likely will not go 300 degrees per hour near the end of the firing.

Whatever you fire to,  Orton cones (108 degree type) will bend at the prescribed temperature if you go 108 degrees per hour in approximately the last 250F of the firing. This is where the majority of the heatwork is done so subtract 250 degrees from your cone temp and the final segment will end up about 2 hrs 20 minutes if  your kiln has enough power to keep up. As far as holds and power cooling, these are things individuals usually develop for their glazes and their desired look after experimentation..

Neil is right,  do you normally fire cone 10? Cone 10 glazes? Cone 10 Clay?

[ArborRoadPottery]

Hi all! 

Yes I usually fire to cone 10, with cone 10 glazes and cone 10 clay because that is all my old studio would allow. Unfortunately the workers at that studio were careless, constantly breaking pieces by dropping them, or losing them completely. As soon as another kiln became available I jumped at the chance to use it. I am trying to use up the high fire stuff I have before switching to a lower fire for good. 

[ArborRoadPottery]

If I could use up the last of my cone 10 glazes at a lower firing temp, I totally would. But for now I feel stuck. 

[Bill Kielb]

On 8/4/2019 at 2:32 PM, ArborRoadPottery said:

If I could use up the last of my cone 10 glazes at a lower firing temp, I totally would. But for now I feel stuck. 

Do you have the recipe? If so you may be able to try adding enough Boron and get them to cone six. (Prox. 0.15 B2O) to test and see if you want to use them up in that way. Cone 10 glazes fired to cone six often end  up very dry matte look. Some  actually prefer the look for non durable items.

Just a thought though

[neilestrick]

The addition of Frit 3134 or Gerstely borate, often as little as 3-5%, will usually get it down to cone 6 without problems. It's not the most scientific way to do it, but you don't want to be mixing up more glaze if you don't have to. You'll have to guesstimate the volume of glaze you have, but with just a few test tiles you can work it out in small volumes then math it up to the full batch.

[ArborRoadPottery]

7 hours ago, Bill Kielb said:

Do you have the recipe? If so you may be able to try adding enough Boron and get them to cone six. (Prox. 0.15 B2O) to test and see if you want to use them up in that way. Cone 10 glazes fired to cone six often end  up very dry matte look. Some  actually prefer the look for non durable items.

Just a thought though

It's prepackaged dry mix from Aardvark clay. I wonder if they could tell me what to add to change the recipe enough to make these all cone 6.... 

[neilestrick]

Take 200 grams of the glaze with the appropriate amount of water, add 2% (4g) 3134 or Gerstley, mix it with a stick blender, dip a tile. Add another 2% (4g), mix, dip another tile. Repeat up to 10%. Fire off the tiles to cone 6 and see what you get. Maybe put them all on a slab in case they run.

However, if you've still got cone 10 clay, then you'll want to go ahead and fire to cone 10 because your clay will not be fully vitrified at cone 6.

[Bill Kielb]

As Neil mentioned but you may want to fire a test tile of the basic cone 10 glaze with no addition to see what it looks like at cone six. Some people love the look and some glazes melt well at cone six for various reasons.. Remember, under-fired glazes are not necessarily durable. If it’s not fully melted it likely is not durable so any gloss that appears matte at the lower cone is underfired and probably decorative only for good measure.

How can this happen you may ask? Many recipes were made by trial and error so for instance I finally got around to analyzing the chemistry of our cone six studio glazes and three of them contained so much boron they looked like 04 chemistry. When I fired them to 04 ....... perfect melt! Hard to know if you don’t have the recipe.

[Magnolia Mud Research]

13 hours ago, Bill Kielb said:

 …  Many recipes were made by trial and error so for instance I finally got around to analyzing the chemistry of our cone six studio glazes and three of them contained so much boron they looked like 04 chemistry. When I fired them to 04 ....... perfect melt! 

Bill, 
This is a good example that using low fire glazes at mid-fire temperatures isn't as bad as the generalizations so frequently stated by some of our colleagues.   
 

LT

[Chilly]

Depending how much clay and glaze you have in stock, it might be cheaper to sell/throw/give it away and buy new, than to fire your new kiln to cone 10.  Take into any calculations the extra cost of firing, and the wear and tear on the kiln elements.