Expert: Sam Kelly - 4/7/2010

Question
Hi Sam,
I have a 10 cub ft electric kiln. Front loader  It is computer controlled.
It has a top vent (not powered) and two door vents.during the firing cycle.  
I am unsure of when to close or open the vents . I usually fire to B.B.C. .
I have had numerous suggestions as to what to do re the bungs and none seem to match up with anyone elses. Can you please advise? thankyou, Jill Guillemin.

Answer
Hi Jill, bungs and vents on electric kilns have 2 purposes, letting out moisture and aiding in the cooling down process.

For bisque firing all water is out of the clay at 600degC. The purpose of the top vent is to allow this moisture out, the outlet size for this part of the firing on a kiln the size of your only neeeds to be a little larger than a golf ball.
After 600degC you can close it off completely, however I always leave a little gap through the whole firing, about as wide as a pencil and about 2 inches long.

For glaze/glost firing the top bung hole/vent can be left closed, however I leave my 'pencil' gap through the whole firing, I have no problems.

The door bung holes remain closed through all operations except to view cones and assist in the cooling down, they must never be taken out untill the cooling cycle has reached 200degC.

Sam