Craig Clark on mon 21 feb 05
John, I've been doing a quick cool down to 2100F and then starting the
slow decent. I take it from your post and having looked at your pots
that 1900F works perfectly well before starting the slow cool. Is this
correct?
Thanx
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
John Hesselberth on mon 21 feb 05
On Monday, February 21, 2005, at 09:29 AM, Craig Clark wrote:
> I take it from your post and having looked at your pots
> that 1900F works perfectly well before starting the slow cool. Is this
> correct?
Hi Craig,
Yes it does for me. Two (things) happen (or you want to happen) when
you cool Waterfall. First is crystal formation. Not much of that seems
to happen before you get down to about 1900, but then it is a slow
process to grow crystals--hence the need for slow cooling. The second
is phase separation. You can often see 2 glassy phases (presumably one
boron rich and the other silica rich) in the glaze. I honestly don't
know where that starts or how long it takes, although I see essentially
none when I cool fast. So 1900 is where I have evolved to start the
slow cooling, but I am not in a position to say that is optimum. I
suppose a better way to say it is that is "in range".
Regards,
John
John Hesselberth
http://www.frogpondpottery.com
http://www.masteringglazes.com
Neal on mon 21 feb 05
I just did my fifth glaze firing. I noticed a big
difference in the cone 6 temoku glaze that C. Harris posted
back in March 1999 in this glaze firing with a slow
cooldown compared to the previous two firings. I started
the cooldown at 2000 F.
His post with the recipe is here:
I don't have Mastering Cone 6 Glazes with me to compare the
ingredients to waterfall brown.
When my kiln cooled on its own, instead of a programmed
cooldown, this glaze resulted in a reddish brown--similar
to the cone 10 Ohata red glaze that I used at one of the
local craft centers. With the slow cooling, it looks a lot
like the middle photo of waterfall brown that John posted
the link to earlier.
Neal
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