Between candling and firing

[CCLACC]

Hello everyone,

I'm new to this so I appreciate your help. I'm working with a Geil gas kiln and had a small question between candling and firing. I realize that when setting the candling you open the damper and close the kiln door and peeps. Once pilots are ignited you then close down the damper and let it soak. When you're ready to bring it up to bisque fire (cone 06) and let the gas in, do you open the door and damper? Or do you keep the doors closed in while letting the gas in? Would appreciate the proper protocol for the transition between candling and firing. 

[Bill Kielb]

Candleing
So maybe better to think of the why first.There generally are two answers. Possibility 1- to slowly warm up the wares and drive off the moisture and thoroughly dry everything out.slowly before we reach steam producing (ware shattering) temperatures. To do this, we need minimal heat, maybe some pilots, a bit of an open damper unless we want a ton of sooty carbon and, the door can be closed or …… cracked open to let air circulate, let water vapor out, and to further slow down how fast it heats. We are just trying to stay under 212 f for a number of hours to dry slowly.

Possibility 2. - we want to slowly heat up a large number of wares evenly, maybe overnight to get an early start the next morning, this time its probably less useful to crack the door as we want to retain some heat and again we set our damper to a minimal opening.to avoid a bunch of soot and we want to warm up the smoke pipe anyway to get a nice updraft going while trapping a little heat so maybe all the wares can warm slowly to maybe 700 - 800 degrees overnight.

In both scenarios when ready, the kiln operator turns up the gas slowly and opens the damper appropriately to match a desired rate which is likely in the range of 100 - 500 degrees per hour.

Notice there really wasn’t a point where the damper is fully shut during firing and really no specific point where everything was shut off, closed and then restarted. The damper and gas pressure are simply managed for the purpose to hold heat in as desired, manage the firing rate and maintain a suitable firing environment (Oxidation or reduction)

Also notice opening the door was optional and mainly to help dry things out as well as slow down the firing rate. In a gas kiln it’s really not necessarily a required step. Folks develop their firing preferences for various reasons but speed of firing is probably the basic reason. After all, plenty of air will go right up the flue if you let it by opening the damper 

So when firing, close the door if cracked, open the damper as needed to trap as much heat as practical without smothering the firing and generating soot (for oxidation firings) while slowly raising the gas pressure to achieve a desired firing rate.

This dance between gas pressure changes and damper opening are your tools to advance the firing till the very end.

[CCLACC]

Thank you, very helpful and clear! Appreciate it Bill!