I'd suggest buying some new cones! And then trust your timer...watch to
see how long it takes for the mechanism to trip the safety shutoff.
Also, use 3 large guard cones that are visible through the peep holes.
The guard cones should be one cone hotter and one cone cooler than the
desired temperature. I put the guard cones on a brick right by the top
peephole, or the second from the top. You want to arrange them so that
you can see all three through the peephole. THe coolest cone should be
on the left side, the desired temp cone in the middle, and the hottest
(overfiring cone indication) cone should be on the right side. So, in
that way, when the coolest cone melts, it wont knock over the middle
cone. They sell some little bricks that are actually holders for these
3 big cones so they won't tip over. If you don;'t understand what I'm
talking about, email me again, and I'll try harder or give you my phone
#. You didn't mention what temp you are firing to, I don't think, but
if you are firing to bisque, it will be a bright yellow orange. Start
watching your cones when you approach a really bright orange. through
the peephole every 30 minutes. As you fire, over time, pay attention to
what color heat you are seeing through the kiln peeps when you are at
the shutoff temp and right before. You will come to recognize those
colors and let them help you gage how hot your kiln is know what to look
for, etc. When the middle cone bends over half way, you are done! Turn
your kiln off and note how long it took you to fire to that temperature.
Next time, set your timer for about 15 minutes or 30 minutes longer.
and be ready to watch your guard cones closely through the window close
to the time it took you to fire this test kiln. If you have to turn up
your kiln dials, make sure to note how you do it on your test firing so
you can repeat the same timing next time.