Kiln Sitter cone for witness cone

[milksnake12]

Hello!
Have a quick question on using kiln sitter cones as witness cones. Got me first kiln over the weekend and did a small bisque fire to test it with about 5 mugs with different clay bodies in the bottom of the kiln (on a shelf 1/2 inch off floor). I was firing to 04 and got a stand to hold the small kiln sitter sized cones upright to use as a witness. I got only a slight lean out of the witness cone on the shelf with the mugs. When doing research I realized in all the images I was looking at, a larger cone or self supporting cone was used. Do the smaller kiln sitter cones slump over like a larger cone when used as a witness cone? Or did the bottom of the kiln really not fire to the right temp?

[liambesaw]

They don't slump the same way.  I tried them after I ditched my sitter for a computer and they weren't even close.  Maybe not enough mass to carry itself down when it gets hot, I think they need the pressure from the kiln sitter to bend

[Hulk]

Hi M! Good question.

I'm still assuming the small cones indicate same as the bigger ones, if set up per manufacturer's instructions.

I make up "cone packs" (guide, target, guard - one each) using a strip of clay for each one, where each cone is set to the required angle; probably best to make them up well ahead of time, so the clay is thoroughly dry. I've a good idea how damp the clay can be and not blow up, haha, guess why.

A cone pack on each shelf, along with the sitter's cone, gives an idea how uniform the heating was. My kiln runs cool at the top shelf and a bit cooler at the bottom, which we mitigate by staggering the half shelves such that the cooler spot "sees" more element, also by loading a bit less densely... 

 

 

"They don't slump the same way."

   Interesting! I'm seeing the small and large cones reflect heat work identically.

[milksnake12]

Thanks! Looks like I'm off to buy some larger cones.

[liambesaw]

5 minutes ago, Hulk said:

Hi M! Good question.

I'm still assuming the small cones indicate same as the bigger ones, if set up per manufacturer's instructions.

I make up "cone packs" (guide, target, guard - one each) using a strip of clay for each one, where each cone is set to the required angle; probably best to make them up well ahead of time, so the clay is thoroughly dry. I've a good idea how damp the clay can be and not blow up, haha, guess why.

A cone pack on each shelf, along with the sitter's cone, gives an idea how uniform the heating was. My kiln runs cool at the top shelf and a bit cooler at the bottom, which we mitigate by staggering the half shelves such that the cooler spot "sees" more element, also by loading a bit less densely... 

 

 

"They don't slump the same way."

   Interesting! I'm seeing the small and large cones reflect heat work identically.

I set them up as witness cones like that, along with cone 6 self-supporting ones and they were showing at least half a cone less compared.  

I still have basically 6 boxes of mini cones that I figured I can't use anymore, so if you're saying they work I'll give them another shot

[milksnake12]

Worth a try Hulk.

I'll grab some larger ones and run some tests side by side and see if they slump differently. 

[Hulk]

I'm interested in what others are seeing, large cones vs. the small ones.

The big ones cost more, however, easier to use and see.

The small ones are cheaper, harder to use and see, however, they can be fitted to a kiln sitter - double duty!

The bars are more precise for the sitter (the sitter's trip point is too easily influenced by the taper of the cone, yes?), but almost useless for anything else.

I'm cheap, so will stick to the smaller cones; I've some big ones that previous kiln owner threw into the deal.

Repeatable, that's important to me - still lots of learning out ahead! A bit overfired - where cone 6 has bent over far enough to touch toes - causes problems with two of my glazes...

 

 

[JohnnyK]

I find the self-supporting cones more convenient since I don't have to deal with making a "cone pack"...

[Min]

From Orton re small cones:

"Small Cones can also be used on the kiln shelf as miniature witness cones when space is limited. They require mounting in cone holders or plaques at an 8° angle and a width of 15/16 of the cone exposed above the cone holder. Small Cones used on the kiln shelf deform at about 9°F before Large or Self-Supporting Cones of the same number."

[liambesaw]

9 degrees isn't much, maybe I had them buried too deep, 15/16ths exposed is hard to eyeball on these little guys haha

[Min]

4 hours ago, milksnake12 said:

did a small bisque fire to test it with about 5 mugs with different clay bodies in the bottom of the kiln (on a shelf 1/2 inch off floor). I was firing to 04 and got a stand to hold the small kiln sitter sized cones upright to use as a witness. I got only a slight lean out of the witness cone on the shelf with the mugs.

Going back to this, I don't know how big your kiln is or if you were using a kiln sitter or if it's a single or 2 or 3 zone computer controlled kiln so this might be a bit of a ramble. I'm guessing it's a kiln with a kiln sitter? If so then the cone in the sitter will be approx 1/2 way up the height of the kiln. When firing a mostly empty kiln it's not going to fire the same as if it was packed, I would expect the bottom to be cooler than the cone in the sitter. Same deal for a single zone kiln with a controller. 2 or 3 zone kiln should be a bit more even but again being mostly empty will have an effect on the firing.

[Mark C.]

Large cones melt as noted above at different temps than small cones. Toy will have to learn the differences if you want to use small cones. The norm is use large cones only for manual viewing. small cones for kiln sitters. 

[milksnake12]

Did a side-by -side comparison with small and large cones about an inch apart on each of three shelves. The results were the same on each shelf - the large cone was bent significantly more than the small cones. 

[liambesaw]

5 minutes ago, milksnake12 said:

Did a side-by -side comparison with small and large cones about an inch apart on each of three shelves. The results were the same on each shelf - the large cone was bent significantly more than the small cones. 

That was my experience as well, although since the results were the same each time, you COULD use that angle as a reference, just mark it on a paper.  Thank you for reporting back

[Min]

@milksnake12, thanks for posting your results. How much of the cone was above the clay pat before firing? I'm wondering if the one in your image is in too shallow.

[Hulk]

Thanks MS!

From Orton website (same as Min posted, above), emphasis added , "Small Cones used on the kiln shelf deform at about 9°F before Large or Self-Supporting Cones of the same number."

Perhaps that's a typo, per MS results, also experience with large/heavy vs. small/light things (made of same stuff) softening, e.g. candles, when the temperature change is slow enough...

Orton's "Cones and Firing Booklet" (.pdf file) seems to  indicate the opposite:

"While not recommended, Orton Small Cones can also be used on the kiln shelf in place of larger cones. Because they are smaller, higher temperatures and more heat are required for them to bend (see page 19). When used in this way, the Small Cones require mounting in cone holders or plaques. (See mounting cones, page 6). "

The temperature equivalents chart, however, doesn't supply comparable F/hour rates - there's 108 and 270 for Large Cones, 540 for Small Cones.

Hmmm, from Clayart thread, "...Dawson told me, small Orton cones were formulated to bend more slowly than large cones to counteract the kiln sitter rod's influence, and that of their horizontal orientation."

Not sure I'm believing that! Also from Clayart thread:

"Small and large cones do deform at different rates.. there is more mass in a
big cone to respond to gravity. But small cones work just fine as visual
cones. Orton recommends an 8 degree lean, and the small cone sticking
15/16th out of the cone pack. The real issue is that the large and small
cones do not deform at the identical temperature. So, it doesn't matter if
you use large or small visual cones, but the cone number and state of bend
is not directly interchangable from large to small.

With the small peeps of electric kilns I find small cones more convenient,
and I only have to stock one size."

Well, I'm still learning, looking for repeatability, and, still cheap, will stick with the small cones. I also find the small ones easier to see, thanks for that LA!

I'm shooting for small cone 6 to look like the small cone in the image MS posted, and about 40 minutes of hold ~100F below peak.

[milksnake12]

@Min Great catch Min! I measured and I did have a little to much cone showing. I made some more seated to the correct depth.  

[Min]

I think with cones the devil is in the detail. 8 degree angle, which face of the cone is placed on the side dropping forward, exposed part of the cone above the clay pad or plaque, placement in the kiln. Good research @Hulk, sounds like an email into Orton to clarify might be warranted. 

[Hulk]

Message sent, will copy back any reply here.

fwiw, small cone height ~28mm (base flat), hence dry pad (or plaque) ~1.75mm; a thicker pad/plaque would require more heat for same bend, yes?

Nice countertop MS - looks just like our'n!

[Mark C.]

I suggest a phone call to Orton-that will settle this issue for sure.They can tell you the offset temp at cone 6.  As you can see the small cones melt at different temps in a cone pad. Makes sense to as they make them for cone sitter use and the rod is pushing down on them.

My fellow teachers from Alfreds always said big cone for visual looking small cones for sitters. I think that is still true today. Once you figure the offset then maybe they can work for you 

[Hulk]

Confirmed that same material is used for small, large, and bar cones, but not all cones - some #s have different formulations between types, that's good enough for me, however, was promised an answer on 5,6 and 7 (should have asked 0-10, hrm)

While on the line, pointed out aforementioned typo, Engineer agreed the small cone description on small cone webpage "...is backward." and the .pdf is correct. We might see that updated (I'd like a slice of pizza for everytime I got somewhat backward - we'd have a party.).

Meanwhile, am good for now using small cones for witness, shooting for cone six 'bout 1:30 per "Orton Cone Positions" chart, as that's where the ware comes out better than when a soft seven, better that solid five but no movement on six. Results.

While I'd like to see small cones have all the temp/hour columns on the heat work chart, not caring about that much now ...having not even noticed afore, heh.

[Min]

Thanks Tom!

I'm a little confused after reading your post, are they saying this bit ""Small Cones can also be used on the kiln shelf as miniature witness cones when space is limited. They require mounting in cone holders or plaques at an 8° angle and a width of 15/16 of the cone exposed above the cone holder. Small Cones used on the kiln shelf deform at about 9°F before Large or Self-Supporting Cones of the same number."  should read 9 degrees F after Large or Self-Supporting cones of the same number?

"Confirmed that same material is used for small, large, and bar cones, but not all cones - some #s have different formulations between types,..." Sounds like they are talking about the difference between the iron free cones versus the ones with iron. 

 

[Hulk]

Hi Min, 

Engineer agreed that

"Small Cones used on the kiln shelf deform at about 9°F before Large or Self-Supporting Cones of the same number." 

is a typo, and

"...Small Cones can also be used on the kiln shelf in place of larger cones. Because they are smaller, higher temperatures and more heat are required for them to bend (see page 19). When used in this way, the Small Cones require mounting in cone holders or plaques. (See mounting cones, page 6). "

is correct.

Regarding the composition, question was are small, large and self supporting cones - of same cone number, same line - made of same material! Where cones of different number are formulated differently - hence they bend at different temperature. This was a point of clarification, and related point, that the temp difference between small and large is due to relative size.

 

[Min]

8 minutes ago, Hulk said:

Where cones of different number are formulated differently - hence they bend at different temperature.

Definitely, they would have to be or else they would all bend at the same temp which really wouldn't be very helpful. Iron free  cone versus same number and size cone with iron, do they bend at the same temp? Doesn't look like it from the quote below, like they say use the same type of cones when comparing them. "The temperature equivalents are slightly different for the two series.  Therefore you should use all "standard series" or all "iron free series" between cone 010 and cone 3."

[Hulk]

Heard back from Orton - in writing; the person who answers that type of question may have been at a conference.

The small cone description has been changed on Orton's website, now reads (emphasis added) "Small Cones used on the kiln shelf deform at about 9°F after Large or Self-Supporting Cones of the same number."

As for formulation differences between Large, Self-Supporting, and Small cones (of same type and number), per Orton Engineer, large cones made without coloration are like small cone formulation, cone 4 through 8 (large cone boxes labeled with "b" after the cone number are made with same formula as small cones). Small cones are "original" Orton formula; some of the Self-Supporting cones were re-formulated - the new formula didn't work well for small cones used in a sitter.