soak?

Soak is to hold at a given temperature for a certain amount of time. You should be aware that doing so will essentially be firing to a higher temperature than what you may have programmed in as the temperature you want to reach if you are firing by a programable controller rather than a cone. Your kiln manual should give you the appropriate information.

has a very nice schedule for firing cone 6 glazes. I also highly recommend their book.

is there any way to soak at a given temperature using a kiln sitter type shutoff, besides using duct tape on the lever and a stopwatch?

regards, charlie

Here is John's latest firing schedule.

Bert Gibson

Wow, I have no idea how to hold a temperature for a given time on a non-programmable controller.... I'll be interested to hear on this one.

If you have a temperature controller could you just turn them all to low at around the cone you are firing to and then turn them up as the temperature drops? You would have to at least have a pyrometer for this though... And you would have to have a higher cone than you wanted to fire to in the kiln sitter, watch the temperature or cones at around the temp you wanted and then manually turn off the kiln... It would be a real dance and experimenting to find what works.

Hold the kiln at the top temperature. This gives time for gases to be released and reduces the risk of pinholing.

I was told that 20 minutes at any top-temperature is enough, but I see that some use 30. I am guessing that the longer you soak, the more sure you are that things go right. Would like to read from those of you with experience here.

Marianne

The problem with the "duct tape" approach is that it won't hold at a given temperature. The elements will still be fully on, and the temperature will continue to rise just as if you had no sitter at all. The only way it would "hold" would be if your kiln was maxed out already, which is doubtful since it approaches the max temperature ever more slowly.

You might be able to use an "infinity switch", which is like the control on an electric oven or range. The control itself heats up when the current to the kiln passes through it, and the heat causes an internal expansion. When it expands to a certain (settable) amount, it trips off the current. Then the control starts to cool, and turns itself back on. The trick here is that you would have to rig the sitter switch to activate the infinity control instead of shutting down the kiln, and the infinity control would need to be pre-set to the right setting, by trial and error. You could do that initially with a thermocouple to see what temperature you can hold with any given setting. Also, when the sitter activated the infinity switch, it would have to start a timer to shut the whole works down after the soak.

None of this would be terribly difficult to do, but it might be simpler to just get a real controller!

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Home of DaqGen, the FREEWARE signal generator

that's what i was afraid of. the kiln only cost me 300, so i hate sinking more than that into just the controller. i might just sell it when a controller kiln comes along in the paper.

thanks, charlie

Well 30 minutes is what I do and it seems to work. As someone else mention though if you have a soak it alters the overall heat work and so you will get a higher cone drop than the actual temp that you set your kiln to. So you have to do some runs with cones in to set your temp for the cone that you want.

Bob,

I *Soak* my Olympic top Loader with a Kiln Sitter & timer by Shutting off at the main when the sitter drops, over-riding it by lifting the latch, pressing the button and lowering the latch GENTLY, setting the timer to the required length of time, setting the Infinity switch to 4.5 (three position switch: medium), and turning on the main again (takes longer to write it than do it!). Usual soak time: 30 minutes for earthenware, 40 for Stoneware.

Steve Bath UK

In article , Bob Masta writes

I guess if the OP is willing to do the timing manually, he could just wire the infinity switch in parallel with the sitter switch. Before the sitter drops, it's switch will be closed so it will take all the current and the infinity switch will be bypassed. As soon as the sitter switch opens, the infinity switch will get all the current and carry on from there until shut down manually.

If one had an infinity switch available, this would be a fairly easy way to go. Dunno where is the best place to pick up one cheap. I reckon that an old oven or rangetop control might do the job. Might be worth playing with, if you're handy with electrical stuff.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Home of DaqGen, the FREEWARE signal generator

May I say what a scary image that forms....

What's the problem? This only requires 2 electrical connections, connecting the infinity switch across the kiln sitter switch. I'm assuming some minimal degree of electrical competence, for example so that the infinity switch is in a metal box and not dangling in the breeze with exposed connections flying about. This is really just an extension of the basic kiln sitter circuit.

Of course, the infinity switch needs to be properly set to prevent overfiring. The first time, I'd set it full-on and watch when the sitter trips. The infinity switch will then be running the kiln. Back off on the control until it just clicks off, and watch to see that it cycles on and off, holding some average power.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Home of DaqGen, the FREEWARE signal generator

Here in Europe, I haven't come across the use of cones, actually, though I am sure some people use them. But even at my pottery-dealer, I can't say I have seen cones in their catalogue.

Besides, it also depends on where in the kiln stuff is, doesn't it?

I would like to know - as you have slightly mentioned - the effects of soaking longer. I know that my teacher soaked her stuff a bit longer, and that was the end of "bubbles" on some of my glazes.

Just starting with the kiln, so all teachings/experience/thoughts are most welcome!

Marianne

As gas is escaping from the clay (Sulfer, Oxygen, Carbon, Hydrogen to name a few elements that escape as a gas) it forms bubbles in the glaze. If you do a 'soak' at the right temperature, you are keeping the glaze liquid long enough for all the gas to escaped, then your glaze 'heals' and is without holes or bubbles in it. Another reason for a 'soak' is that if you want crystals to form in your glaze which is what gives the beauty to some of the glazes many of us like, this happens at a certain temperature and you maximize the size and number of crystals by holding it at this temperature. That is why sometime people will put a glazed pot in a bisque firing. It is at the right temperature for crystals to develop.

Wow - cones usually orton cones IMO are essential. see

experience is with electric kilns so I will talk about that. When your elements are new the temperature that you set your kiln to and the actual amount of heat work that your pottery gets are usually pretty close to what the pyrometer reads. Some kilns are very even from bottom middle and to top, but cones should be used to actually check this so that you know what your specific kiln is doing.Heat work - like when you cook something, if you cook it at a lower temp you need to cook it for longer, but it will still end up cooked. Same goes for pottery in a way, it is not the actual temperature that is gained, but the amount of heat work that is done. So if you do a soak which IMO is advisable to get rid of gases, it alters the amount of heat work and to find out what that is you need to use cones.As elements age it takes longer to reach temperature and therefore more heatwork. So again you need to be having cones in the kiln regularly to see what your kiln is doing.Could you understand that, I found it difficult to put into words.

In article , Annemarie writes

I think that was very clear.

Steve

I have noticed in ceramics magazines like Ceramics Monthly, that when they show work of European artists quite often it says something like "Fired to 1150C" instead of giving a cone number as is typical here in the USA. So I guess your experiences in Europe may be typical. Since the same final temperature can represent different cones depending on the rate of heating (faster heating = less heat work = lower cone for same temp), the two systems are not really interchangeable. But I suspect this is not really as big a problem except for really finicky glazes, and once you get to know your kiln you will adjust as needed. It's just that in USA somebody will say that "well, this Floating Blue recipe is supposed to be cone 6, but I find I get better results at cone 5", whereas I imagine in Europe you would say something like "I get better results firing 20C lower" or whatever.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Home of DaqGen, the FREEWARE signal generator