The effect of Firing profiles on glaze texture

Now, I show one glaze in three different cone 10 firings of varying lengths, with distinct final temperatures.
The two slower firings have holds at different temperatures both in the up-fire and down-fire part of the firing cycle.

I developed these firing profiles using the Orton Cone prediction calculator, formerly available on the Orton Foundation Web Page.

Firing One

fast firing to cone 10 at 2310 deg F.

Inside of pot:

Outside of pot:

bowl is ~ 4 inches in diameter

Firing Two

slower firing to a low cone 10 at 2190 deg F
This firing has longer holds in the up-firing than Firing 2 above.

Inside of pot:

bowl is ~ 6 inches in diameter

Firing Three

slower firing to cone 10 at 2220 deg F
This firing has long holds in the up-firing and longer holds in the down-fire as well.

Inside of pot:

Outside of pot:

bowl is ~ 4 inches in diameter

Firing profiles

The differences between the first fast firing and the other two firings is primarily in the top temperature reached, and the lengths
of the holds getting to that top temperature.

The top temperature, 2310 deg F for the first, 2190 deg F for the second, and 2220 deg F for the third.

The temperature ramp is steeper for the first firing, slower for the others.

Up Fire profile 1

Faster and hotter:

150 deg F an hour to 250 deg F

400 deg F an hour to 1800 deg F

300 deg F an hour to 2050 deg F

120 deg F an hour to 2310 deg F with a hold of 20 minutes at 2310 deg F

Down Fire Profile 1

300 deg F an hour to 1750 deg F then a half hour hold at 1750 deg F

300 deg F an hour to 1700 deg F then a three hour hold at 1700 deg F

25 deg F an hour to 1650 deg F then a one hour hold at 1650 deg F

Up Fire profile 2

Slower and cooler

150 deg F an hour to 250 deg F

400 deg F an hour to 1770 deg F

40 deg F an hour to 2130 deg F

13 deg F an hour to 2150 deg F / hold 4 hr

13 deg F an hour to 2170 deg F / hold 2 hr

13 deg F an hour to 2190 deg F / hold 2.5 hr

Down Fire Profile 2

300 deg F an hour to 1900 deg F then hold 2 hours

300 deg F an hour to 1850 deg F then hold 2 hours

Up Fire profile 3

Between firing 1 and 2 in both speed and final temperature

150 deg F an hour to 250 deg F

400 deg F an hour to 1770 deg F

300 deg F an hour to 1860 deg F

120 deg F an hour to 2140 deg F

13 deg F an hour to 2190 deg F / hold 2 hr

13 deg F an hour to 2220 deg F / hold 2 hr

Down Fire Profile 3

300 deg F an hour to 1900 deg F then hold 3 hours

300 deg F an hour to 1850 deg F then hold 3 hours

Clay body is a grolleg porcelain from Tacoma Clay Art Center.

glaze composition