Pat Chesney on sun 27 oct 96
Concerning insulating brick with layers of castable.
I had the pleasure of spending Friday afternoon with Rafael at our facility
in Waco where we discussed kiln coverings. We used metal lathe (the
expanded metal sheeting used for stucco) to keep the covering from
compressing the 2-3 inch of fiber lining we used on our single wall
catenary arch kiln. By putting the lathe over the fiber, it bore the weight
and the bulk of the coating, leaving the fiber mostly loose and not
cemented to the covering. The lathe holds the covering and prevents it
from cracking also. I did wish that I had installed foil over the fiber-I
would next time.
We have fired to 1900 F several times and the water-proofing layer we
used, Mortar cement and fine sand 50/50, has held up well and it does not
get overly hot. (You can rest your hand on the structure comfortably. Even
opposite the fire chambers.)
Even the chimney, which gets considerably hotter than the insulated walls,
is holding up to the heating and cooling cycles. We will put more layers on
the kiln after the big number of firings for our craft fair are finished.
(maybe the kiln will cool down for a little while then. :) )
With a single hard brick surface and 2-3 inches of fiber, the inside of the
covering registered a cool 130 F while the kiln was at 1900 F. It does hold
the heat for a long time.
Now a question about cooling the pots. I have read many theories about the
speed of firing up and down with stoneware. I have heard that rapid rise is
not as critical to avoid as rapid cooling. What is considered rapid
cooling? We are using a white stoneware that matures at cone 10. It is
Dillo White from Armadillo Clay in Austin. It is similar to HS 2 from Hood
Supply in San Antonio. After we cool to 500-600 F we remove the first layer
of bricks from the door. At 400 F. We open up the holes and remove the
final layer of bricks. At 200-150 F we remove the pots so we can load the
kiln again due to a backlog of pots. All of this takes about 5-6 hours from
600 F.
Is there a difference from bisque to the glazed ware? Is the theory correct
about cooling being more important than rising? How long do you guys take
to go up to say, 1850 F for bisque and 2350 F for maturity -and then how
long back down? Our electric kilns fall much faster than the salt kiln does
and it doesn't seem to hurt them.
Thanks for the help.
Pat Chesney
Pat-Chesney@easy.com
Waco, Texas
| |
|
