John Baymore on wed 29 oct 97
------------------
Hi all.
As an addendum to my recent post of some private e-mail on solubles and
carbon trap and shino........
The outer layer of glaze that has all that high soda content migrated into
it is not only =22wet=22 and fluid early on during the UP part of the cycle,
but remains the last part of the glaze to =22freeze=22 during the cooling
cycle. Hence the ability to easily trap carbon on the cooling cycle as
well as the heating cycle. (Mel's sticks.)
If one is firing in a wood kiln, volatiles from the wood ash (like sodium)
tend to get onto the outermost layers of the pieces. This causes similar
(but not as dramatic) fluxing of the outermost glaze layers, and can cause
carbon trapping on glazes that don't normally tend to =22trap=22. Places of
early direct flame impingement and strong draft flow get more of this
stuff. If you throw soda (carb. or bicarb.) or salt into the kiln too (as
seems to be the practice of an awful lot of woodfirers these days), that
does the same thing. Residual soda on the brickwork of the kiln helps
promote this earlier in the firing.
BTW....while I am on the subject. An awful lot of the pieces you see these
days in the mags that are labeled as simply =22woodfired=22, are a bit
misleading. An awful lot of them are fired in wood kilns, but are also
lightly salted (or soda'ed). So there is a tendency to associate the
effects seen on these pieces to woodfire , not residual or light soda or
salt. They look a bit different than typical straight woodfire, although
under certain circumstances, can look very much alike.
Best,
.......................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752
JBaymore=40Compuserve.com
| |
|
