Mile Hi Ceramics, Inc.
CLAY, Glazes, Equipment, Supplies since 1954
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Orton Pyrometric Cones - Order Cones Online Here

About Cones
Pyrometric cones measure "Heat Work "(the effect of time and temperature). Pyrometric cones are slender pyramids made from about 100 carefully controlled compositions. Each cone number is unique in measuring temperature within a small temperature range (less than 30°C). Cones measure the amount of heat absorbed. As the cone nears its maturing range, it softens and the tip begins to bend, drawn down by the influence of gravity. A cone number is a measurement of  Heat Work.  Clays and glazes are formulated to mature at specific cone numbers. When a manufacturer labels a glaze to fire at cone 05, it means that in order to mature, the heat work required to deform an Orton Large Cone 05 must be accomplished.

Cone Styles
PYROMETRIC BAR	JUNIOR	LARGE	SELF- SUPPORTING

Pyrometric cones are remarkably sensitive and accurate devices for measuring the effects of heat – time and temperature.
When used correctly they are capable of indicating temperature differences within a very few degrees.  
Use Self-Supporting or Large Cones whenever possible. 
Self-supporting Cones give the most consistent, repeatable performance due to the fixed mounting height and angle.

Mile Hi Ceramics, Inc. carries only Orton Pyrometric Cones    Order Cones Online Here

Using Witness Cones

Use witness cones in every firing: Both Kiln Sitters and Controllers can fail due to mechanical malfunction. In either case, properly using witness cones will insure that you don’t experience a serious melt-down.  Cones are cheap; kilns are not

Witness Cones are the only way to measure heat work. When a manufacturer refers to a witness cone number, they are referring to a large or self-supporting Orton Cone.
                   (Junior Cones are not used as witness cones).

To use witness cones, select 3 cones as follows:

• A Guide Cone - One cone number below your goal.

• A Fire Cone - The cone number you wish to achieve.

• A Guard Cone - One cone higher than your goal.

Place standard large cones in a holder or cone plaque designed to hold them at the proper eight degree angle. If using self-support cones, their special built-in base will place them at the correct angle. Place cones in order: Guide\Fire\Guard. (For example, to fire to cone 05, place the cones facing left 060504). This allows each cone to melt without interfering with the others. Cone plaques should be visible through your kiln’s spy holes during firing so that you can monitor your progress and manually shut down if automatic devices should fail. Additional cone plaques can be placed in other areas of the kiln for analysis after firing is completed. They will tell you if your kiln fires evenly throughout or where your hot and cold spots are.

Orton maintains the highest standards of quality control in the testing and production of their pyrometric cones. Orton is known industry-wide as the leader in temperature measurement and control.

Cones are crucial to successful firings of your valuable work - don’t take chances with less expensive brands.

Orton Cones are the best!

Order Cones Online Here

Cones are used in sequence of at least three cones in the desired heat range..

Order Cones Online Here


The temperature listed on the cone chart is the temperature at which that cone deforms when heated at a specific rate. If the rate is changed, the temperature will change. This is why a pyrometer reading may not always appear to match your cones.
If a discrepancy occurs during a firing between a pyrometer readout and a cone deformation,
always follow the cone.

Use Self-Supporting or Large Cones whenever possible.
Self-supporting Cones give the most consistent, repeatable performance due to the fixed mounting height and angle.