How to soak with a manual sitter, or, priorities

[mxdsa]

Hello,

I have an electric Knight kiln with a manual Dawson sitter. My experience is around 20 firings, both bisque and cone 10. The glaze books I've been reading really emphasize the firing schedule, including a soak. My firing schedule is a simple gradual increase (the lid and three levels, L-M-H) over the coarse of 7-8 hours for cone 10. My first question is, how do I soak after the kiln turned off (via the cone mechanism) - do I simply turn it back on, on medium or something, for the soak time? I imagine there's a better way.

Second, is considering the soak an appropriate priority for my situation? For context I'll be making my own glazes. The goal is predictable, controlled results in my electric kiln. Should I be giving more attention to other aspects of the process?

Ah, third question in this topic - can a manual sitter be upgraded on this kind of kiln?

Any suggestions would be great! My primary reference book is High Fire Glazes by John Britt.

Thanks, Caleb

[Denice]

I used a dual Skutt  digital pyrometer  to do my soaks.   I would be near by at the end of the firing so I could hear the click of the bar dropping down.   I would take a pencil like stick and raise the bar back up,  push the button back in and gently lower the bar.  I had my  pyrometers  in a pair of peek hole plugs,  I was firing a large Skutt so I need two pyrometers.   Skutt's peep hole plugs are hollow so it is easy to cut the end off.   The thermocouple sticks out into the kiln about 5 inches so you have to leave space for it when you load the kiln.  Once you have the kiln at the temperature you want you can keep it at that temperature by adjust the knobs.   I start out by turning the upper knob to medium.   I fire to C6,   the glazes aren't that different than C10,   more premade glazes and formula's available  and your wiring will last longer.  I think the Knight kiln  could be 50 years old,  I threw away a Paragon that age a few years ago.   When I took the metal jacket off the brick turned into a pile of sand,  my kiln guy had told me it was to old to be worked on.  The condition of your kiln makes a big difference.    Denice

[Hulk]

Hi Caleb, welcome to the Forum!

My experience so far has been with a manual kiln fitted with three switches, each with four positions (Off Low Medium High) and a sitter mechanism.
I'd bought the kiln from the original owner, who was moving and had decided to get a new and smaller kiln after completing their move. They kept their pyrometer, but passed along an almost new shelf set, the original shelves that weren't completely ruined, an assortment of shelf supports, several boxes of cones, and a container of red iron oxide. I ordered up a pyrometer and more cones right away.

Any road, for holds, drop and holds, et cetera, I watched the pyrometer and operated the switches.
I kept detailed notes, which are helpful*.

Q1 When the sitter drops and pops the button when I'm wanting to fire more, I just push in the button back in and go.

Q2 I soak at about 1500F during bisque firing, on the way up and down - the idea being extended time (with oxygen, via fan powered kiln vent) helps to burn away more of the stuff that causes problems, especially in black, red, and buff clays. The day afore firing I heat up to about 200F then shut all down, idea being drive off residual moisture; the next day, I'm starting off full bore.

For glaze fires (I'm doing a solid cone 5), I'm heating up to 2112F, then dropping (all three switches to low) to 2012F and holding there for twenty to thirty minutes, the idea there being to allow some time for little pinholes to heal over, for the glaze is still soft enough to do so, while the clay cools a bit and stops off-gassing ...or somewhat, any road, it seems to help. I read about drop and hold here and on Tony Hansen's website digitalfire.com 
I toggle the switches and watch the pyrometer.
From there, all switches to low while the temperature falls; when 1850F is reached, all off and the kiln vent off for the long cool down, looking forward to opening the next afternoon when ~200F is reached. I do the slow cool to 1850 because it seems to ameliorate some glaze defects.
Also, for the first part of the drop from peak, I'll leave the top set of elements on high while the middle and bottom are on low, idea there being to get a bit more heat work on the top level, which always seems to run cool.

Q3 A control box that plugs into your power, which your kiln then plugs into is likely the simplest automation choice, where the box relies on a pyrometer and turns off/on the kiln. 

I didn't mind being "the controller" when firing my first kiln, which I did for over four years.
Taking detailed notes to refer to later helps.
Hanging around the kiln may be bad for one's health, the fumes! I rigged a 400 CFM fan up to an overhead hood to whisk away most of the heat and also the fumes - that really helps!

*Cone packs on each level, compared against the time and temperature notes, voila! - with some little experience, putting the kiln glasses on to check the cones becomes less important, however, I still set kiln packs to check out afterward...

When, and how long you may choose to hold particular temperatures, and/or at what temperature ranges you choose to move slowly, is purely up to you and what you're trying to accomplish!
I'm looking forward to operating a numerically controlled kiln with zone control (more than one pyrometer).

[neilestrick]

First, I would start working at cone 6. Your elements aren't going to last vey long, and the total lifespan of the kiln will be greatly shortened, by firing to cone 10. Also, you'll have a much easier time holding/soaking/slow cooling if you're working at cone 6, because at cone 10 you won't be able to hold well with manual switches. At cone 10, as soon as you turn a switch to medium it's going to drop in temperature a lot, and then you'll have to turn it back on, and then off, and then on, over and over and you still won't maintain temperature very well. At cone 6, going to medium won't have as big an impact and you'll have a lot more control. That said, holding temp is a lot more difficult than just slowing down the cooling.

Soaking shouldn't be necessary in most cases. It's usually only needed if there's a specific glaze problem that can be fixed with a soak.

[mxdsa]

Thank you all so much for the advice! Sounds like the first thing I need is to buy a pyrometer.

@neilestrick I'm not sure why I chose cone 10 originally, but your reasoning seems sound. Would you think that my stoneware clay will be okay to fire at 6 instead of 10? (Or does that question need more information to answer?)

@Denice and @Hulk - thank you. It's helpful to read process descriptions of how people actually do it. 

Many thanks!

[Denice]

How much of the clay do you have?   I would use it for working on your throwing techniques and not worry about firing it.   My throwing class in college we spent most of our time throwing and then cutting it in half to check the thickness of the walls.  We could fire three pieces  to keep,  you can also use a odd  clay in mold making.   I throw away any clay that is around plaster.  if the plaster gets in your clay you can have explosive results when fired.   When you buy new clay make sure that it is in the same firing cone that your  glaze is,  there is some clay's out there that has a long firing range.    This can cause trouble with your glaze fit.     Denice

[mxdsa]

Great info, thank you

[Denice]

I keep only C6 clay in my studio,  I don't want any low fire or high fire causing me headaches.   I have seen a couple of firings where someone put some low fire work in a high fire kiln,  the low fire clay melted all over the other pots.   I am currently finishing a mural that I am using six different clay's  for there different colors,  speckling and texture,  They are all C6 with the same shrinkage rate.    Denice

[Callie Beller Diesel]

On 5/9/2023 at 8:30 AM, mxdsa said:

Second, is considering the soak an appropriate priority for my situation?

I think it’s important to understand why you’re doing a soak at a given point in the firing. Why does the work need the heat, or the chance to even out the kiln’s temperature at the point you’re soaking at? Are you even having a problem with something and adding a soak will fix that problem, or are you just going by guidelines that someone else wrote down because it seems like a likely starting place? There’s nothing wrong with the latter, just understand that like the pirate code, they’re more like guidelines than actual rules.

On 5/9/2023 at 8:30 AM, mxdsa said:

Ah, third question in this topic - can a manual sitter be upgraded on this kind of kiln?

Yes, and there are loads of how-to threads on changing your kiln from a manual to a digitally controlled one in the equipment use and repair threads. Neil is also a kiln tech, so he can advise you on how-to. It’s a bit of a project, and it depends on how comfortable you are with doing work with electronic components. 

 

[Denice]

I agree with Callie about your comfort level when working with electronic components.   I am not comfortable at all,  I always hired a kiln technician to repair or replace any needed parts on my kiln.   My husband started repairing them when he retired,  his job was very stressful and wasn't interested in working on a kiln on his days off.   I am wary of electricity, my dad was a bad electrician and was always trying to repair the old knob and tube wiring  in our house.  It got to a point where we were afraid to touch any sinks or faucets.   Denice

[neilestrick]

@mxdsaIt's not simple to fully convert a manual kiln to a digital system because the control box on the manual kiln isn't made to house the digital kiln parts. There's no insulating baffle, and the box isn't necessarily deep enough to house the parts needed. You can't just replace the Sitter with a digital controller- there are other parts needed (a transformer and at least one relay- usually two or more). The easiest solution is to buy or build a small control box that houses all the parts and hangs on the wall next to the kiln. The kiln plugs into the control box, and the control box plugs into the outlet on the wall. You use the Sitter as a backup safety device by putting a cone in the Sitter that's one cone hotter than the intended peak temp, then push the power button on the Sitter and turn the switches to 'high'. Then you start the digital controller and it cycles the power to the kiln to control the rate of climb.

Here's a picture of a control box I built and installed for a customer last week. It has a Genesis Mini controller, which is perfect for this type of setup since it only uses one thermocouple. The power cord comes out the bottom, the kiln plugs in on the left. Inside is a 50 amp relay, and pilot relay, a transformer, and all the wiring to make it work. It's not simple if you've never dealt with wiring before, but the good news is that you can buy a complete box just like this, although it'll cost you more than $1000 with a touch screen controller. This box is hooked up to a Duncan kiln, which has an early generation analog automatic system that I had to disconnect in order to work with the digital controller. That shouldn't be an issue with your Knight kiln, though, as I've never seen one with anything other than simple switches.

 

[Pres]

Sorry folks, but for future reference and search clarity I have moved this strand from In the Studio here with Equipment and Repair.

 

best,

Pres