[Clayart] first firing disaster in soda kiln

[Robert Harris]

​You might be better off dissolving the soda and spraying it in. We use
either a simple pumpable garden sprayer (make sure you get one with a metal
end), or a compressor driven sprayer with the nozzle attached by a hose to
a 5 gallon bucket. As I recall we use about 3-5lbs of soda dissolved in
about 5 gallons of water.

Robert


On Sat, May 5, 2018 at 9:26 AM, Helen Stone <helenestonepeony at gmail.com>
wrote:

> 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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