[clayshapes]

I got a new kiln two weeks ago with an electronic controller (yay) and am very pleased with it. But the pre programs for fast and slow bisque have pretty slow ramp ups -- an 04 bisique program runs between 10-13 hours. A fast glaze firing takes 4-5 hours at cone 6.

This is the opposite of my old prehistoric kiln (Duncan) -- which had a dial and three settings -- overglaze, ceramic and high fire. It was set to ceramic for an 04 bisque (or lowfire clay glaze) took about 6 hours. It was set at "high fire" for a cone 6 glaze - and took about 10-14 hours (depending on the age of my elements).

I never had any issues with the faster bisque firing schedule with the old kiln - which I couldn't control.

I understand that the slow ramp up on the new kiln is to release water smoke etc. safely -- but I wonder if this is really necessary. Could I be bisque firing more quickly - and if so - how do others program their controller for a faster bisque?

I'm using cone 6 stoneware, and also occasionally cone 04 earthenware. My controller is Bartlett model V6-CF

[neilestrick]

My recommendation to my customers is to use the 'Fast Bisque' and 'Slow Glaze' settings. With these you will rarely have any problems, and won't waste a lot of energy on firings that are unnecessarily long and slow. They are set up to provide good all-around firing schedules that will work for most anyone. That said, I have been know to do a 'Fast Glaze' setting for cone 04 bisque. Shortens it up to about 4.5 hours. It works for my clay, but for some clay bodies it may be too fast to adequately burn out all the stuff that needs to get burned out in a bisque. You could always do a custom program that just modifies the pre-programmed choices by speeding up each rate of climb a bit.

[clayshapes]

Thanks Neil -- I guess I'm confused about why my "fast bisque" takes 10-13 hours and my fast glaze only take 4-5 hours. Like I said, the opposite of what my old kiln did. The manual does state it will take this long for the bisque - I'm just wondering why it ramps ups so slowly, compared to my old kiln.
I'll keep with the program for a while longer though -- my kiln is only a couple weeks old. And it's possible this very slow ramp up it will help prevent warping -- which is a bit of a problem for one of my clay bodies. Do you think this is a valid assumption?
I know experience is what will answer my questions best -- but I am always curious to hear about other peoples' experiences, too.

[Chris Campbell]

I also would not expect a bisque firing to take 10-13 hours ... Nor the glaze be so fast. Strange ... Maybe they know something we don't?

[neilestrick]

Bisque firings are made to go slower to prevent steam explosions at the start of the firing, and to make sure all the organic materials are burned out at the end of the firing. Bisque firing too quickly is often the cause of glaze problems. Glaze firings can be faster because there is little risk of explosions, and the bad stuff is already burned out.

Your old Duncan was essentially a manual kiln, although it did have a relay system. The relays were cycled at a certain rate, but the rate was not adjusted for the desired cone or rate of climb. The kiln didn't know how hot it was going, so it just plodded along until the cone melted. It didn't know the difference between a bisque or glaze firing. Plus those old Duncan kilns were not the most efficient kilns in the world, so getting to cone 6 was a bit of work for them. In computerized kilns, the computer knows how hot it needs to get, and the programs are set to fire slow enough to avoid issues, but fast enough to not waste electricity. The controller constantly makes adjustments to stay on schedule regardless of the density of the load or other factors.

[clayshapes]

Chris -- that's exactly what I said to the tech where I bought the kiln -- but I guess Bartlett figures that since the bisque is so slow and complete -- there's no need for very slow ramp for glaze firing. The manual specifically says that glaze firing can be fast. At first I thought there was an error in the manual -- how can a glaze firing only take 4-5 hours????
I can report, however, that all goes well with this schedule -- my glazes look the same as usual and the stoneware is ringing like a bell. I suppose it's the balance between the two -- and I guess I should be happy that the longer firing is at a lower temp - easier on the elements and the electricity bill -- though not likely by much.

[clayshapes]

Thanks Neil - I was typing my reply to Chris when you were sending yours.
For all it's lack of brains - I have to say the old Duncan worked pretty well. But I appreciate the fast glaze on my new kiln (Euclid). It just seems so counter intuitive to me since I'm used to the old way.

[Lucille Oka]

clayshapes, on 07 February 2013 - 06:25 AM, said:

I got a new kiln two weeks ago with an electronic controller (yay) and am very pleased with it. But the pre programs for fast and slow bisque have pretty slow ramp ups -- an 04 bisique program runs between 10-13 hours. A fast glaze firing takes 4-5 hours at cone 6.

This is the opposite of my old prehistoric kiln (Duncan) -- which had a dial and three settings -- overglaze, ceramic and high fire. It was set to ceramic for an 04 bisque (or lowfire clay glaze) took about 6 hours. It was set at "high fire" for a cone 6 glaze - and took about 10-14 hours (depending on the age of my elements).

I never had any issues with the faster bisque firing schedule with the old kiln - which I couldn't control.

I understand that the slow ramp up on the new kiln is to release water smoke etc. safely -- but I wonder if this is really necessary. Could I be bisque firing more quickly - and if so - how do others program their controller for a faster bisque?

I'm using cone 6 stoneware, and also occasionally cone 04 earthenware. My controller is Bartlett model V6-CF

I have recently purchased a kiln with the same Bartlett model V6-CF controller. You can use the 'Vary Fire Mode' (on the left side of the panel) to write your own program for the bisque as well as the glaze firings. It is just one of the many features of the Bartlett V6-CF.

[clayshapes]

Yes I know, of course, that I can write my own program -- my inquiry was about what kind of program -- how to change it up in a safe way. Although I think I'll leave it be -- Neil's explanation makes sense.