Fast bisque using controller

[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]

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.

[Gloria Meier]

Hi There

 

Im using MC 101 low fire clay. We just received a new kiln with the V6-CF Bartlett control panel, can this be fired on a fast bisque setting? I don't really want to write my own program as I am not familiar with this.

 

Any advice would be appreciated. 

Gloria 

[Bill Kielb]

I’ll jump in here. Bisque firings take more time (Generally) because of what is happening with the clay body. Effectively burning out all the unwanted contaminants can and often does take time to burn out. So the simple answer for slow versus fast bisque would be is it effective for your claybody. For Thick sculpture work maybe not. For thinly thrown pots, maybe fine. It needs to be verified by testing.

the fast glaze program is very similar in that if it works for your clay and glazes then that is what you should do. Basically the fast glaze program goes 570 degrees per hour and the slow glaze goes 400 degrees per hour. The slow glaze has a drying segment of 150 degrees per hour to 250 degrees and the fast glaze has no drying segment.

which is best? The one you have tested and are satisfied with.

[neilestrick]

Most of my customers use Fast Bisque and Slow Glaze. They work for most situations. If you have large or thick pieces, you may want to use Slow Bisque. Fast Glaze is too fast for a lot of glazes. Glazes appreciate a little longer, slower firing.

[Bill Kielb]

10 minutes ago, neilestrick said:

Most of my customers use Fast Bisque and Slow Glaze. They work for most situations. If you have large or thick pieces, you may want to use Slow Bisque. Fast Glaze is too fast for a lot of glazes. Glazes appreciate a little longer, slower firing.

We have found the opposite to be true in our studio. All bisques are slow to eliminate issues later with incomplete burnout and believe it or not everyone prefers  fast glazing and are happy with the results. Of course a fast glaze in a larger kiln fully loaded ends up to be 7 or more hours anyway because of the loading so it works for them. I think test and set your preference accordingly, knowing that fast bisque may have a bit more risk from time to time with incomplete burnout of some bodies.

now picking a bisque temp everyone likes, another whole debate!

[glazenerd]

Gloria:

on page 17 of your manual is the program segments for slow-fast bisque cycles.

both speeds have a drying segment 150-250, with an extended hold to drive off any moisture in the pieces.

from 250-1000: slow ramps at 200F and fast at 300F.  Both speeds have a quartz inversion ramp from 1000-11000 @ 100f an hour. The fast bisq goes through inversion faster:.

from 1100-1924F- both programs follow the same  ramp cycles.

The application of each ramp would be:

if you stuff your kiln to full capacity, dry stack pieces: then slow bisq allows for uniform distribution of heat.

if you are firing large, heavy, pieces with large foot rings (shelf contact), dark or red bodied clays: also use the slow speed.

If you are firing porcelain, white stoneware, cups, spoon holders, pieces under 5lbs. (2.2 kilos) then fast bisq is fine.

if you are firing large porcelain, white stoneware , large foot rings, etc. go back to the slow bisq.

in essence: the type of clay, the sizes of your pieces, and how full you stuff the kiln determines fast or slow bisq.

Tom

[Bill Kielb]

I’ve attached a screenshot of the two schedules at cone  six, in the event that you find it easier to see these side by side. Bartlett makes this manual available for download in  the event that the original is lost. Basically slow bisque is slower through all stages than fast bisque allowing time to burn off  the stuff we want to burn off and prevent same stuff from getting into our glaze finishes or remaining in our clay bodies only to be released later during the glaze firing.

studios may prefer this because often they fully load, stack and load mixed clay bodies. Trial and error is usually the only way to figure out whether it works for your clay and loading. Basically slow is better than fast at ensuring all the contaminants are gone.

 

 

[neilestrick]

16 hours ago, Bill Kielb said:

We have found the opposite to be true in our studio. All bisques are slow to eliminate issues later with incomplete burnout and believe it or not everyone prefers  fast glazing and are happy with the results. Of course a fast glaze in a larger kiln fully loaded ends up to be 7 or more hours anyway because of the loading so it works for them. I think test and set your preference accordingly, knowing that fast bisque may have a bit more risk from time to time with incomplete burnout of some bodies.

now picking a bisque temp everyone likes, another whole debate!

I should have specified, I was referring to customers who use low fire white bodies like Gloria is using, which don't seem to have burnout problems, and where the fast glaze to cone 05 is only 4 hours.

[Bill Kielb]

On 1/13/2019 at 11:12 AM, neilestrick said:

I should have specified, I was referring to customers who use low fire white bodies like Gloria is using, which don't seem to have burnout problems, and where the fast glaze to cone 05 is only 4 hours.

Understood - Fast glaze  to cone 6 is also programmatically under 5 hours as well. My only point is it either suits your glazes or not and regardless of body suits your required burnout or not  Still determine by test, some folks go fast all the time and it works for them. Some folks slow down after ruining a few things and realizing the cause.