Gary Ferguson on sat 5 apr 03
Resent
----- Original Message -----
> Victoria:
>
> My guess is the firing is just making another problem more evident. If
your
> firing process has not changed, I would assume you are developing cracks
(or
> micro cracks) during the drying or bisque stage, and then these cracks are
> further enhanced (and made visible) with the violence of the Raku firing.
>
> Gary Ferguson
> Raku Clay Artist
> Nampa, ID 83687
> Visit my site at http://www.garyrferguson.com
> Subscribe to Just Raku Newsletter at http://www.JustRaku.com
>
>
> ----- Original Message -----
> From: "victoria henricksen"
> To:
> Sent: Wednesday, April 02, 2003 10:23 AM
> Subject: help! problems with raku
>
>
> > please help....I have started having some major problems with pieces
> cracking in the raku kiln. I have done about 40-50 firings in this kiln in
> the last 6 months, but recently the majority of my pieces have cracked.
The
> pieces are about 6x6", press molded relief tiles. up until a few firings
> ago, i had never lost a tile, but now my rate of loss is 75-100%. I am
using
> 2 different kinds of clay, Laguna's raku, as well as Seattle's columbia
> white stone....both of these clays are giving me the cracking problem.
> When this problem had first started occuring i thought that it was due to
> the fact that the tiles had been bisqued to a hotter temperature,
rendering
> them less resistant to thermal shock....i normally bisque my raku ware to
> 08, but i had a problem with the kiln and it fired to approximately
05...but
> once i realized that these pieces were all cracking, i stopped using the
> tiles from this batch. Since then i have been using tiles from 2
subsequent
> 08 bisques and have s
> > till had
> > the same problem! I have always kept a firing log, and so i can
> ascertain that there is not much difference in the firing 'ramp'....i have
> tried going much slower, i've 'candled' the kiln on low fo
> > r 15 minutes before sloooowly climbing, but with no better success rate.
> I am using a kiln which i built from a 50gallon drum, lined w/ fiberfax,
> with a removable lid on top (not top-hat style), and a propane burner. The
> tiles seem to be cracking before they go into the reduction bins, as the
> cracks are impregnated with carbon. When i first started using this kiln,
> the weather was much cooler (winter, with snow on the ground)...now of
> course it is warmer....this seems like the only major variation, but it
> doesnt make sense to me that this would cause the cracking.
> >
> > ...same kiln, same clay, same tile design, same firing schedule,same
> glazes....
> >
> > have i missed something??? i am getting desperate as i need to fill
> some orders PDQ....if anyone has ANY suggestions please offer them up as
at
> this point i am willing to try anything!
> >
> > in desperation, Victoria
> >
> > PS oh and FYI, i dont spray with water, i just fire the pieces until
the
> galzes melt and then transfer them to reducing bins filled with sawdust,
> newspaper and a few other combustables.
> >
> >
> >
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> >
> >
>
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