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.

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! Use in every firing.

Why use Cones?

Firing ceramics is much like baking, except temperatures are higher. Ceramics can be fired over a range of temperatures. Some products have a wide firing range while others have a narrow range. Firing to a slightly lower temperature requires the ware to be held for a longer time, just as it would be done if one were baking a turkey. This is because it takes time for the ware to absorb all of the heat needed to properly "cook" the piece. We refer to this absorption of heat as 'heatwork'. When the amount of heatwork for two firings is the same, the pieces will look identical, even if one is fired to a higher temperature for a short time and another is fired at a lower temperature for a longer time. Since cones measure heatwork, all manufacturers recommend the cone number to which their product should be fired.

Self-supporting Witness Cones

Orton recommends Self-supporting witness cones because they are easier to use and less subject to bending variation. Many people use witness cones every firing and the 3-cone system periodically to check for changes in the kiln. Cones are saved to compare different firings. When more than a half cone difference occurs, it usually indicates a problem exists. This gives you an opportunity to fix the problem or change the way the kiln is being fired to avoid future problems. Cones are the best way to inexpensively monitor your kiln.
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 firing cone.
   A Firing Cone - cone recommended by manufacturer of glaze, slip, etc
   A Guard Cone - One cone higher than your firing cone.

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.
Example-firing to cone 05, place the cones facing left 06 05 04 This allows each cone to melt without interfering with the others.

Many products used today, such as porcelain and lead-free glazes, need to be fired within a 2-cone range. The 3-cone system can be used to determine temperature uniformity and to check the performance of the Kiln-Sitter® or electronic controller. The 3-cone system consists of three consecutively numbered cones:

Cones Help Evaluate Kilns
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!

Cone Bending

Both temperature and time and sometimes atmosphere affect the final bending position of a cone. Temperature is the predominant variable. We refer to the temperature as an equivalent temperature, since actual firing conditions may vary somewhat from those in which the cones were originally standardized. Using charts available from Orton, an equivalent temperature can be determined by measuring the final bending position of the Cone, if the heating rate is known. Orton Self-Supporting Cones duplicate their bending behavior with a standard deviation of 2.4 angular degrees or less than + 2°C.

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

We accept Purchase Orders from Schools & Institutions and offer generous school/wholesale discounts.
Please call Mile Hi Ceramics

KILNS: FIRING ACCESSORIES: PYROMETRIC CONES