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Seems we are shifting between Celsius and Fahrenheit a fair bit so I'm adding Links to Orton Cone Charts in both to save people looking them up who might not be fluent in both. If anyone needs it there is some really good information regarding the behaviour of cones and how the rate of temperature increase during the final 1 1/2 - 2 hours of the firing effects the final cone, also on the links below.

Orton Cone Chart in Fahrenheit

Orton Cone Chart in Celsius

edit: There seems to be an error in the information regarding small cones in the above information to the right of the charts. "Typically, small cones will deform 7-10 degrees C earlier than a self-supporting cone, so the temperature values for a self-supporting cone can be used to determine an equivalent small cone temperature by subtracting 7-10 degrees C (or 12-18 degrees F)." This contradicts what it says in the Orton Cone Firing Booklet: "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." 

Edited by Min
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Recall we received clarification from Orton on small vs large cones: 


The website was corrected (the .pdf was ok)

      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."

My take is still (mostly) repeatability - how the glaze and clay behaves when cone is bent thus, hence difference between large and small cones matters when a) switching to the other cone type (I like the small ones) and/or b) when sharing firing info with others.

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I do remember that thread Tom, it's what made me question what the info on the cone charts says. The blurb with the charts is reading the opposite of what the Orton Booklet is, hopefully they will change the oversight. I emailed them, will update my post if they change anything.

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