"DKat" wrote in message
...
Marianne, every time I think of this I keep coming back to you having your
peep holes open (and I'm fairly certain that is what you have open if
there are 3 of them, they are on the side and they have plugs that go in
them). If you are having as long a soak as you say, and there isn't an
issue of the glazes being on too thick or bad glazes to begin with then
you really are left with the kiln getting cold spots from the peepholes
being open. Bubbling doesn't happen when the glaze is cooling off. It
happens when the glaze is melting and gases in the glaze are being
released. The soak at top temperature allows for the heat to be evenly
distributed and for the melt to even out (bubbles to mend). If this isn't
happening, then I can only think that the cold draft from the peeps is
'freezing' the glaze before it can settle.

Donna

These are not peep-holes, they are airing holes and their use has been
explained to me many times (regarding different glazes and their firing) by
my dealer - who also refurbished and sold me that kiln. I hope that's clear.

Leaving the holes open for the whole firing was a one-time event that
probably was the reason for the bubbling on many of the pieces - as the room
temperature was from 17-24 C, so the air being let in was too cold.

Normally, I leave the hole at the bottom and the hole in the lid open until
650 C and then close them until the kiln has cooled to 200-250 C - at which
time I may open them to let the kiln cool a little faster, as it takes hours
and hours for the last 200 if I don't. From an old American potter, I
learned the smart rule that nothing is ready to come out of the kiln until I
can hold it with my bare hands. Patience is hard, but smart.

The long hold temperature was an experiment to see if it would help. It
didn't help much, so I am back to 20-30 minutes. My teacher also uses these
glazes, and I am on my way over to her in a few minutes to take a look at
her firing curve, as I may be using her old one. She does not have many
bubble problems any more. Will be interesting to see what her curve is.
BUT - her students usually glaze with less experimentation than I do - and
probably thinner as well, so her curve might only bring me closer to a
sollution to my most difficult glazes (the ones with the beautifier).

I am on the way to getting a new controller that will let me also controll
the cooling process. I hope and pray that that will let the glazes go from
boiling to liquid without leaving bubbles/pock marks. In the mean time, I am
staying away from the beautifier and trying combinations of matte glazes
instead. The more glossy a glaze is, the more chance of it bubbling. So I
will wait a few weeks until I can have more control.

I hope this sets your mind to rest.

I have also been thinking about why Americans can not do without cones, and
I wonder if Europeans "simply" use glazes that are more geared to top
temperature than to heat work in total. In any case, hubby has suggested
that I add the weight of what I put into the kiln onto my kiln log - thus
knowing what mass is in the kiln each time and getting an even better handle
on which firings work for which glazes, etc

I'm in a stress getting stuff finished to fire so I can take it with me on
Monday, so not sure when I will stop by here again..

Keep smiling :-)

Marianne