All Firing Schedules

"C10RPL" Firing Schedule

Plainsman Cone 10R Firing

Every gas kiln is different so this schedule may not work for you if your kiln does not cool at the same rate or maintain the same atmosphere. Our kiln is brick construction, downdraft, four natural gas burners, about 30 cubic feet. It fires evenly top-to-bottom and front-to-back. We have had and used others but none of them equaled the quality of firing this can produce. It was built by Luke Lindoe.

It can rise while reducing so we do not do a separate body and glaze reduction (with an oxidation climb between). Reduction is consistent throughout the kiln, enough to produce a clear bluish flame at the peepholes (with some yellow at the damper). We soak for half an hour in oxidation at the end. To prevent temperature rise during this phase we turn the gas pressure to almost zero (allowing it to drop a little). On shutdown, we seal it up but the temperature still free falls (although slower than a fibre kiln would). We open it at about 200F two days later.

Related Information

How many degrees between these cone positions?

I was consistently getting the cone on the left when using a custom-programmed firing schedule to 2204F (for cone 6 with ten minute hold). However Orton recommends that the tip of the self supporting cone should be even with the top of the base (they consider the indicating part of the cone to be the part above the base). So I adjusted the program to finish at 2200F and got the cone on the right. But note: This applies to that kiln at that point in time (with that pyrometer and that firing schedule). Our other test kiln bends the cone to 5 o'clock at 2195F. Since kiln controllers fire cone 6 at 2230 (for the built-in one-button firings) your kiln is almost certainly over firing!

Gas kiln near cone 10R in the Plainsman Clays studio

It is old, but nothing we have ever used fires as evenly and reliably as this downdraft kiln. It was built by Luke Lindoe in the 1960s. I have used it through my entire life as a potter since the early 1970s. Two burners at 2 inches oil-column will take it to 1000F fairly quickly, but it takes 4 burners at 4 inches and 20 hours to get it to cone 10. I can judge the back pressure and degree of reduction by the length and color of the flames at the peepholes and color of the flame passing the damper at the back. Changing the damper position by an eighth of an inch during reduction is enough to discern a change in the flame.

Cone 10R load of fired ware in Plainsman gas kiln

It fires evenly in temperature and atmosphere from top to bottom, front to back. Nothing more can be expected for any studio kiln. We use the C10RPL firing schedule.

Another view of the gas kiln in the Plainsman clay studio

Example of a modern automatic firing reduction gas kiln for use by studio potters

Courtesy of Bailey Kilns.

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