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Showing FAQs 18of 18    


Can you use small cones as witness cones?

Yes. They must be placed in a clay holder so that they slant 7° from vertical. They do not bend the same as large cones. The small cones take longer to bend because of their size.

... [More]

Can you use small Orton cones as witness cones on the shelf?

We prefer large witness cones, because they are easier to see. Because of the weight, the large witness cones bend sooner than the small ones. However, the difference in bending between the two sizes is minor.

... [More]

How do you position the cones on the shelf so that you can see them through a peephole?

Most people have difficulty seeing the witness cones on the kiln shelf during firing. But if you position them just right, you can see them even at cone 10, when the kiln interior turns white-hot.

Being able to see the cones during firing is ... [More]

How does firing speed affect the pyrometric cone?

During the last 100 – 200 degrees, the firing rate affects the bending temperature of a pyrometric cone. The faster the rate, the higher the temperature when the cone bends.

But the firing speed before the last 100 – 200 degrees has little in ... [More]

How were pyrometric cones developed?

Ceramists of the past judged when the firing was completed by the color of the heat and length of firing. In 1886, a German ceramist named Seger made clay cones that bent when the ware received the proper heat work. He positioned the cones on a shelf ... [More]

I have 15-year-old cones. Do they bend at the same temperatures as the new cones?

In 1996 Orton reformulated some of their cones, because they could no longer obtain the ingredients they had been using. Several mines closed that year. According to Orton, the newest cone formulas are more consistent the pre-1996 formulas.

O ... [More]

I have been using large regular cones. Someone told me I should use only the self-supporting cones for accuracy. Is this correct?

The large regular Orton cones are as accurate as the self-supporting cones provided the regular cones are slated 8 degrees from vertical. The correct slant is built into the base of each type of cone. But it is possible to alter the slant of the regu ... [More]

I lose shelf space when I keep a clear line of sight from the peephole to the cones and the element behind them. (This refers to positioning the witness cones inside the kiln.)

You need to be able to see only one set of witness cones. You don't have to see them on every shelf.

... [More]

I'm having trouble understanding cone numbers. Which is hotter: cone 05 or 06?

Cone numbers without the zero in front (1, 2, 3, 4, etc.): The higher the number, the hotter the temperature.

Cone numbers with the zero (01, 02, 03, 04): The higher the number, the cooler the temperature.

It might help if you menta ... [More]

In a recent firing, 07 and 06 witness cones are flat but the 05 is only starting to bend. The difference between cones 5 and 6 is no where near that large.

Pyrometric cone 06 is 39 degrees F hotter than cone 07. Cone 05 is 60 degrees F hotter than 06. Because there is such a wide temperature difference between 06 and 05, Orton eventually added the 05 1/2 cone.

... [More]

Is it okay to use pyrometric cones that have become wet?

It is okay to use cones that have become wet as long as they were not soaked in water and as long as they still retain their shape. If they crumble, they should be discarded. Air dry moist cones before firing.

... [More]

Is it true that the self-supporting cone is slightly over-fired if the tip bends and touches the shelf?

The self-supporting cone, when fired to maturity, bends downward until the tip is even with the top of the base. If the self-supporting cone tip touches the kiln shelf, the cone is slightly over-fired.

On the other hand, the standard large co ... [More]

My witness cones are not bending. Besides underfiring, why would a witness cone fail to bend?

The cone must be slanted 8 degrees to bend accurately. Tightly packed sections of the kiln will fire cooler than loosely packed sections. If the elements are of the same resistance throughout the kiln, you will also find that the center of the kiln f ... [More]

Should you put pyrometric witness cones on every kiln shelf?

[Note: A witness cone is placed on the kiln shelf of ceramic firings. The cone indicates whether the ware has received the correct amount of heat.]

A. Yes, it is a good idea to place cones on every shelf when you are firing a ceramic kiln tha ... [More]

What is a cone pack?

The freestanding cones (self-supporting) are easier to use than the standard large cones. Results are more consistent, too. However, you can make a cone "pack," or holder, by pressing the standard cones into a small wad of wet clay--just enough clay ... [More]

What is the difference between a standard large cone and a self-supporting cone?

Standard large cones must be mounted in a clay or wire plaque with 2" of the cone exposed above the cone holder. Self-supporting cones stand upright without holders. They have a built-in base that holds them at the correct 8 degree slant on the shelf ... [More]

Why are cones numbered in such a confusing manner?

The most confusing thing about cones is the way they are numbered. But once you understand the reason behind the numbers, the system becomes clear.

Pyrometric cones are numbered from 022 through 01 and 1 through 10. Cone 022 matures at the l ... [More]

Why does the Orton cone chart have three columns?

The three columns in the Orton temperature chart each represent a different firing speed. The 27 degree F column = 27 degrees per hour of temperature rise during the last 90 - 120 minutes.

Digital kilns are programmed with cone temperatures ... [More]

Showing FAQs 18of 18    

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