Orton Witness Cones

    The Orton Foundation started back in 1896 with the establishment of the Standard Pyrometric Cone Company by Dr. Edward Orton Jr. who was a pioneer in developing and applying scientific principles to ceramic manufacturing.  The original purpose of those Standard Pyrometric Cones was to verify and document the proper firing of industrial ceramics.  The products were cones used to witness the firing, hence the name ... Witness Cones.

    Today, with digital controlled kilns, the purpose of the Orton Witness Cone remains the same as it was 1896 ... witnessing the firing of the kiln.  As with advances in kiln technology, the Orton Witness Cone of yesterday has also improved.  No longer is there the need to properly balance and align the Witness Cone, as today's Self Supporting Witness Cones allow for easy placement in the kiln.

Orton Self Supporting Witness Cones

Set of Orton Witness Cones, before and after the firing of a kiln.

    Witness Cones measure the heat-work performed in the kiln firing.  Heat-work is a time versus temperature equation based upon the rate per hour of temperature increase to a specific final temperature.  Witness Cone values are based upon the melting temperatures, as defined by heat-work, of common ceramic and industrial materials.  The average temperature difference between Witness Cone values is about 30˚C.
    Witness Cones are commonly used in sets of Witness Cones.  As illustrated in the drawing above, 3 Orton Witness Cones of adjoining values, such as 03, 04 and 05, are placed on the kiln shelves a minimum of 6" from the wall bricks.  Just prior to the final firing temperature the coolest Cone (05 in the illustration) will over-melt.  At the final firing temperature the middle value Cone (04 in the illustration) will melt into a perfect 90˚ arch.  The hottest Cone (03 in the illustration) will not bend.  Any deviation from the anticipated Witness Cone results will indicate a probable firing problem.  Larger kilns will use multiple sets of Cones to verify the firing results throughout the firing chamber.
    Witness Cones should be used in the modern digital controlled kiln to verify the accuracy of the controller and thermocouple calibrations as well as to indicate loading or element fatigue problems in the kiln.
    Orton Self Supporting Witness Cones are packaged in boxes of 25 Witness Cones per box. 

Dogwood Ceramic Supply stocks the following Self Supporting Cones:

Pricing:

Boxes of Orton Cones may be combined for the quantity price.

Prices valid until December 31, 2008.

Ordering Information:
    All Orton Cones use an alpha prefix and 1 to 3 digit number to signify the correct item number.  SSB is Orton's alpha prefix for Self Supporting-Box.  When ordering Orton Witness Cones always reference the SSB prefix.  The number values can be confusing.  04 is not the same as 4.  And the "0" in 019 is required, because Cone 19 cone exists for industrial customers.

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