Kilns

[This is repeated from a 11/4/22 posting to MemberConnect, by Brenda Burgess]

The last kiln I fired did not go to the temperature I wanted but it was my fault. The glaze colors were good, just different - we were expecting Cone 6 colors but got Cone 4 colors. I consider it a win win because some of the glazes I liked better at Cone 4.

So, I submitted a question to L&L Kilns about time/temperature and even firing of a kiln from top to bottom. I also contacted Orton and got some follow-up information that I wanted to share with you.

Robert at L&L

Cone 6 is not a specific temperature, it covers a range of over 100 degrees based on how fast the kiln is climbing.

For example- cone 6 will bend at 2165F only when the kiln is climbing 27 degrees per hour for the last 180 degrees of the firing. Cone 6 will bend at 2232F when the kiln is climbing 108 degrees per hour. Cone 6 will bend at 2267F when the kiln climbs at 270 degrees per hour.

I knew this already but it really has not "sunk" into my clay DNA yet.

As for uniformity top to bottom- the claim with these controllers is +/- about 1/2 a cone so you're within that range. Uniformity is mostly affected by how far apart shelves are and where they are in relation to the lid and floor. The closer shelves are to each other in the very top and bottom the cooler that area will fire.

Orton Cones

I have attached a cones and firing pamphlet that has some of the information you mentioned. The other PDF is a scanned copy of the measurement template you could use to measure a cone bending point. Print it, cut, and paste onto cardboard.

What the L&L kiln statement is trying to say is that when comparing how two cones have bent, if one is to a halfway point (3 o’clock) and another bent completely to 6 o’clock, that is considered a good result. Most kilns will exhibit some variability in temperature uniformity. The actual difference in heat work between cones like that is only a few degrees.

You may also like the cone bending video on our website, https://www.youtube.com/watch?v=m2zmY4SQkl8

There is a lot more information on our website, found in the resources section of pyrometric cones. https://www.ortonceramic.com/pyrometric-cones-resources

Best Regards,

Thomas McInnerney

Engineering Manager- Pyrometric Products

Brenda

[This is repeated from a 11/5/22 posting to MemberConnect, by David J. Parmenter]

Thanks for the share Brenda!

Very timely too because I was getting an E1 error code for heating ramp too slow.

I got great help and education from the gurus on the Ceramic Arts Network forums. They helped me overhaul my kiln's wiring and I got much improvement in performance, and solved the E1 problem, but it still wouldn't reach temperature. However I monitored the witness cones and I still achieved near cone 6 results at 2146ºF due to a very slow ramp. They also explained a lot of the same information you just shared about loading and even firing. The bottom line is that some kilns just cannot heat as fast as the controller schedules call for. My kiln, kinda like me, needs to take things a little bit slower.

The Cones & Firing booklet will come in really handy as I dial in my next glaze firing.