[Clayart] first firing disaster in soda kiln

[Helen Stone]

My soda kiln fired to maybe cone 11, Hank, like you I could not see the
cone packs from a point midway int he firing, the atmosphere seemed very
murky, so overfired but clay held up nicely. I could only see the cones on
the lowest shelf.   Disaster was that the soda mixes failed to volatilize
within the kiln and very little soda was deposited on the samples.  Perhaps
I was working the damper wrong, think that I fluttered it backwards, i.e.
instead of opening the damper somewhat when introducing soda mixes, I
closed it a lot, then opened it.  I was introducing golf ball sized pieces
on angle iron, also tried a few packets made up of soda ash and borax for
fun.  Also, I was at that point in a great hurry due to possibility of
propane running out, I had four 50 lb cylinders for each of the two burners
but it took five cylinders, I got more quickly, to finish.  I introduced
the soda all within an hour, possibly way too short a time for the amount
that I was using.  I was using the surefire recipe of Gail Nichols with
soda ash, baking soda and calcium bicarbonate , dampened.  The two firing
chambers were awash with turquoise soda mix and the nice protective layer
of refractory mortar with sawdust, etc. that I had laid down in each firing
chamber, had peeled off the walls of the firing chambers.  Fortunately
little damage to bricks.

So, result was over 150 nasty samples of clay and kaolin mixes with every
conceivable type of native slip, all dry and unrewarding, although I do see
the potential for colour with one kaolin, it flashed so beautifully on the
kiln wall at the end of both firing chambers, ha ha, but not on any of the
sample clay squares.  Also at the end of both firing chambers, I had put
hardbrick steps, in order to encourage the flames to go upward.  Not smart,
I needed more of an upward slope instead, evidently the steps pushed back
the flames so that they were confused as to where to go...

 On a positive note, I now have three great new wadding recipes from the
test firing, all cheaper than what I was using.  I am seriously
reconsidering the excusive use of soda and musing about considering a mix
of soda, borax and salt, per Gordon Hutchens, Canadian potter (he was an
American) out west.  He gets great results, but after 40 odd years that is
not surprising, but there may be a lesson in this.  So, I AM CONSIDERING
USING SKINNY CUTS OF HARDRICK TO LINE THE INSIDE OF MY KILN NOW.  Is this
crazy?  I need to do the inside arch also.  As it stands, the first five
rows of brick are hardbrick anyway.  Could be dicey to lay the skinny
slices of brick, I would have to use refractory mortar.  The arch is
another challenge, how to do it without mortar, to do it outside is easy,
to do it inside is harder it seems.  Maybe a bit of mortar, and the arch
needs to end - inside of course - on some sort of hardbrick buttress.  Sigh.

Helen in Ecuador, Rio Yambala
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