electric kiln firing questions

Hi all,

When I was first setting up this kiln I got a lot of great advice from this
group. I've been set up for a few months now and have completed 2 firing
cycles (bisque/glaze) however, I still qualify as a complete newbie!

The kiln is an electric cylindrical kiln, 7 cu. ft. I have some firing
schedules for bisque and glaze that were passed on to me. I try to follow
them as best as possible as my kiln (3 zones) has the old lo-med-hi switches
which don't offer a lot of control. I installed a pyrometer which I rely on
heavily to monitor rates of change. I also use the kiln sitter and witness
cones.

My confusion stems mainly from the relationship between the cones/kiln
sitter/ and pyrometer. For example, when bisque firing to cone 04, the
chart states 1940 F at a certain rate for the regular cone. My kiln sitter
is shutting off at 1979 - 1984 which jibes with my witness cones pretty
well. At the point my kiln sitter goes off I check the pyrometer, and
adjust the controls to hold that temperature for 20 minutes. Is this a good
idea? Should I also be holding the temperature when glaze firing for 20
min? Doesn't holding a temperature just equate to over firing?

More questions: I was told to shut down or start holding when a cone is at
3 o'clock, the orton book says 6 o'clock.

I have a lot of ware that would fit with 4inch posts but they don't seem
tall enough in terms of having enough elements showing between the shelves.
Do you guys use 4" posts ever?

The height of the kiln sitter tube and my thermocouple tube constantly
conspire to interfere with my post height / shelf placement etc. On my
first shelf I cannot use 6" posts because the shelf will be at the exact
height of the kiln sitter, so I have to use 8" posts which wastes a lot of
vertical room. 4" posts on the bottom level gave witness cones that were
only at 2 o'clock when the center shelf ones were at 6 o'clock. Can I just
ignore the warning about having a shelf within 1" of the kiln sitter?

I built my ventilation system myself and have never been sure my downdraft
vent is pulling the right amount of air out of the kiln. It's a 4" duct cap
with a 1.25" sq. hole cut into the face of the duct cap. The duct cap is
then screwed to the kiln side with a 1/4" standoff distance, centered over a
3/8" dia. hole drilled through into the kiln. If I hold a match to the
sighte hole on the opposite side of the kiln with the lid closed it pulls
the flame in for sure, until the kiln gets hot. My lid is also warped a
bit, wouldn't this allow enough air to enter the kiln so I could keep the
sight hole closed up? (at the moment I use the site hole as the air intake
for the downdraft vent.)

If you read this far, Thanks!

Kandor