help with kiln sitter calibration??

[Cones will bend more in a kiln sitter than they will in a cone pack. If you want to confirm this for yourself, put a 018 cone in a cone pack (standing up) in your next fire.] [Usually, there's a screw somewhere that calibrates the needle. You should be able to calibrate it to show 1386 when the kiln shuts off, if you want. Cones react to "heat work" which is heat over a period of time, not to momentary temperatures like the pyrometer.] [It sounds like it's working fine to me. Try it with a pot inside, and see how it does.]

Andrew Werby

Thanks Andrew,

My pyrometer is digital so there is no way to adjust it. I read somewhere that most pyrometers don't adjust for ambient temp. at the end of the thermocouple wire and that some people adjust their numbers accordingly by having a seperate thermometer near the gauge location. Although I'm not sure how those numbers inter-relate.

The kiln sitter manual shows a cone nicely bent to a 90° angle for correct adjustment. Does the cone continue to bend after the shut down? It obviously remain quite warm inside the kiln for hours afterwards. Doesn't this contribute to the bend angle of the cone?

I'm glad you think it sounds fine! It gives me hope!

Thanks again,

Zander

3 things;

Digital Pyrometers do not have an adjusting screw.

Pyrometers measure pure temperature at the instant you look at them. Cones (in what ever situation) because they are akin to clay and glazes, measure accumulated heat-work which is very different and more accurate.

Cones in a kiln sitter do go early so install the next one up, and trust the cone, not the pyrometer for final temperature. However the latter are excellent for telling you how fast you are going up.

Steve Bath UK

In article , Andrew Werby writes

Zander: The pyrometer is NOT an absolute. It can vary as much as 125 degrees. And that's normal!

If the sitter is adjusted as it should be, I would not worry about the cone bending more than 90 degrees. If it looks like a "U", though, I would suggest that you might not have enough weight on the sitter tube assembly. Make sure that the parts swing freely. Do not oil anything in the sitter!

Also, make sure that the tabs on which the cone sit are clean (use a bit of steel wool pad or green pad on them to get them clean, or replace them) and that the bar resting on the cone is clean also. You don't want either part hanging up on the cone (sticking), and possibly delaying shutoff.

If you have an analog pyrometer (with a dial and a needle) there should be a very small screw hole at the center of where the needle pivots (either on the front...most common...or on the back. Moving this screw small amounts will adjust the reading on the dial.

Digital pyrometers also have a similar adjustment. Since you cannot accurately measure high temperatures without expensive equipment, set your pyrometer to read accurately at ambient temperature (use a regular temperature thermometer to determine how accurate it is). Your high temperature will be off slightly then, by maybe 40 degrees, which is no big deal. If you have no access to any thermometer stick the thermocouple under your arm, in your armpit, wait a few minutes for it to reach temp, and adjust the pyrometer to read 98F or 99F (36.5C)

You mentioned a guide telling you the cone temperature. Please be aware that there are three cone manufacturers, and all of them have different temperatures, and also these temperatures vary depending on how fast your temperature rises!. For the test cone, use the fastest temp rise rate in the chart, (for the smallest cone) and make sure the chart is from the manufacturer of the cone.

Confused yet?

I never worry about the condition of the cone in the sitter. You should be using witness cones in your firings anyhow, and shutting the kiln off manually. the sitter is only a safety device, and should not be trusted as "the word" on when your work is fired correctly. Most cones used in sitters will shut off one cone prior to what they are rated for.

Do yourself a favor. Get a good book, and use witness cones. Put your feet up, read the book, and watch those cones in the kiln (through a welding helmet glass...the UV will kill your retinas). I can think of worse ways to spend time. You've invested all that time making the work. Why leave it to a machine to tell you when it's done?

Hope that helps,

Steve: Hate to tell you buddy, but I have a brand-new Ultimax (digital) that DOES have an adjusting screw. You can vary the temp 85F either way with the screw.

The old ones were considered "tamper-proof" and did not, but INSIDE there was a potentiometer that would allow adjustment (don't ask me how I know this)

Best,

instructions.

"wayneinkeywest" wrote in news:Qzbtc.653$ snipped-for-privacy@bignews2.bellsouth.net:

Thanks Wayne, that helps a lot.

A few questions though of course!

1: If the kiln sitter shuts off 1 cone prior to it's rating should I be putting #7 small cones in my sitter instead of the #6 small cones that I already bought?

2: What did you mean by "I would suggest that you might not have enough weight on the sitter tube assembly." I ask this because my last test fire to cone 018 did result in a U shaped cone (bent probably 160°) Although I did this test fire at HI so the kiln sitter went off 48 minutes after I started the kiln.

I'm ready to do my first bisque firing but it seems obvious that I need some guidance. I have not found a definitive source of what time/rate/temperature to set at kiln at for a bisque or glaze fire.

I know this is because there are so many variables in kilns, clay etc but a rough idea would help.

Here is what I know so far (or think I know!) (note my kiln has 3 zones, each has a lo med or hi setting)

Kiln with top peephole left open, downdraft vent on. Start on low or med to approximate a temperature climb of 250° F per hour until it reaches around 1100° F. at this point crank it up to high until the cone level you want is reach ie. cone 04 for bisque or cone 6 for Glaze.

That's about all I know and I feel it's probably at least partly wrong! Doesn't look like much.....

TIA

Zander

Zander:

Do't forget that cones measure heat work, and not just temperature! You can bend a cone in 48 minutes, or 48 hours, depending on how much heat the cone has been exposed to. It's going to vary some from firing to firing, depending on atmospheric conditons, how much the kiln is loaded etc.

I have a similar kiln, but no vent. As any potter will tell you, everyone is going to have their own firing schedule, and we all do. Here is what I use for bisque (to cone 04) since i fire to cone 10:

(04 cone in the sitter)

Peeps out (all three), lid is cracked about 1/2 inch, turn bottom element on low for one hour. Temp is about 100C (212F)

Peeps still out, lid still cracked, turn middle element on low for an hour, then drop the lid and turn the upper element on low for an hour.

When temp rises to 150C, raise the bottom element to medium.

Put in all three peeps.

When the temp reaches 200C, turn the middle element up to medium. When the temp hits 250C, turn the top element to medium.

By this time, it's been about 4 hours all told.

When the kiln hits 300, turn the bottom element to high, at 350, the middle element turns to high, and at 500, the top element.

When the kiln approaches 580C (600 is quartz conversion), I reduce the middle and top to medium, until the kiln passes 600. Around 620 or so I turn everything back to high.

Kiln sitter drops on it's own at 04. I reset the kiln sitter button and timer (if you have one), and reduce the 3 elements to medium for an hour, then to low for an hour. At this point, the kiln should have passed through 600 again on it's way back down. If so, shut everything off and go to bed.

All told, about 9 hours. Don't open the kiln until it's 100 degrees, or the next day.

Some people think that's way too fast a firing, but it works for me.

Personally, I think there are two points at which there is a "danger" level: The point at which water is being boiled off (212F or 100C) and again at quartz conversion (600C). My own personal phobia says go slow for each.

Play with it a bit, and find what works best for you.

Hope that helps, Wayne

Lucky Beggar,

We can't get them over here yet (well I haven't found them UK-side yet). The only one worth having at present is a Taiwan made job; very good value, 2 displays, works with 5 different types of thermocouple, and doesn't eat batteries. I'm trying to find out the maker so's I can import it direct and cut out the middle man (better deal for my customers!).

Steve Bath UK

In article , wayneinkeywest writes

Nonsense! Of course you can! It's not like the UK is 3rd world!

A Kelly search revealed two suppliers in the UK. Go here:

just gotta love having a world of information at your fingertips!

I really appreciate the info Wayne. It's good to have a place to start for sure. I'm going to be hopefully trying this on the weekend and I'll let you know how it goes.

Much Thanks,

Zander

Fitt a Perfect Fire controller , that's what I did , it's 2004 the kilns sitter belong in the last century click here

, they are cheap and easy to fitt , they have the same diamension as the kiln sitter.

cheers

jason