Craig Martell on sun 10 dec 00
Hi:
I've been reading the shino stuff and saw Vince's comment about shinos
without soda ash trapping carbon. I've seen this too, especially in the 35
glaze biaxials that I've done with shinos. The fluxes have been just
nepheline syenite, a local basalt stone, spodumene, and or Fusion Frit 493
( a lithium, sodium frit). I've seen quite a bit of carbon inclusion
(trapping) in the higher flux concentrations of the blends. As the alumina
is increased, the trapping becomes less visible and finally stops. In one
set of glazes I saw some very nice carbon shadow in the lower alumina,
higher silica areas. These were white shinos with a nice carbon
shadow. Blends reveal a lot.
later, Craig Martell in Oregon
Paul Taylor on mon 11 dec 00
Dear Creig
I made some distorted vases and painted some soda ash on them in dollops
and dipped a few in the turf ash bucket by the stove they turned out a
piebald gray green with black areas.I thought they were nice but was a
feared that the customers would not take to them. Now I know its called
carbon trapping I shall make some more. I will tell the customers that its
all the rage in America. This will give them permission to like them as
well.
I am glad I did enjoy the pots. I gave them away to people who I knew
would appreciate them and then forgot about them.
Maybe if I had done a whole series of line blends I would have valued
them more . But since I got lucky I suppose I did not consider the value.
My phycology of creativity and esthetics always amazes me.
I am relieved that I did like the pots as I would be questioning my
ability to judge. Now I only have to question my lack of confidence in that
Judgement and my marketing.
Regards from Paul Taylor
http://www.anu.ie/westportpottery
ps. Tried some old blue glazes and your own. reduced the **** out of them
but no show. My materials are very contaminated there is still a green tinge
and when I used the black iron oxide its even worse . It is frustrating to
loose a glaze because of changing materials more research and hasseling
suppliers. I hate that.
> From: Craig Martell
> Reply-To: Ceramic Arts Discussion List
> Date: Sun, 10 Dec 2000 09:48:21 -0800
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: Shino carbon trap
>
> Hi:
>
> I've been reading the shino stuff and saw Vince's comment about shinos
> without soda ash trapping carbon. I've seen this too, especially in the 35
> glaze biaxials that I've done with shinos. The fluxes have been just
> nepheline syenite, a local basalt stone, spodumene, and or Fusion Frit 493
> ( a lithium, sodium frit). I've seen quite a bit of carbon inclusion
> (trapping) in the higher flux concentrations of the blends. As the alumina
> is increased, the trapping becomes less visible and finally stops. In one
> set of glazes I saw some very nice carbon shadow in the lower alumina,
> higher silica areas. These were white shinos with a nice carbon
> shadow. Blends reveal a lot.
>
> later, Craig Martell in Oregon
>
iandol on thu 21 dec 00
Dear Craig Martell,
The recipes you posted to Clayart #2000-217 are interesting and I =
appreciate that you fire these to cone 10. Thank you for providing this =
information.
However, I would be most interested to know more about the firing =
program you are using, for cone 10 says nothing about the other =
parameters which have to be considered if we eager practitioners are to =
achieve both the rich colour contrasts you indicate and the requisite =
amount of carbon staining suggested by your heading.
Wishing you all the best for the festive season and a prosperous New =
Year.
Ivor Lewis.
Craig Martell on thu 21 dec 00
Ivor sed:
>I would be most interested to know more about the firing program you are
>using, for cone 10 says nothing about the other parameters which have to
>be considered if we eager practitioners are to achieve both the rich
>colour contrasts you indicate and the requisite amount of carbon staining
>suggested by your heading.
Hello Ivor:
I don't actively trap carbon. Some folks do and more power to them. I
look at carbon trap as a passively acquired accent to pots. There are
others on the list who can give you some real directed firing approaches to
carbon trapping. Mel just did a real nice article in CM on "Black Shino"
that goes into this. Hank Murrow has also sought appropriate shino firing
schedules and can tell you a lot more than I can.
My schedule for the shinos is the same as for everything else that I
fire. From ambient temp to cone 06 in oxidation which takes 5 to 6 hours
depending on thermal mass. Heavy reduction at cone 06 measured at 0.7 on
the oxyprobe. As the temp advances to cone 5 the reduction lessens of it's
own accord to moderate at .50 on the oxyprobe. From cone 06 to cone 5,
about 3 hours time. Another hour until cone 8 begins to soften and the
reduction is increased and held at .65 on the oxyprobe until cone 10 is
flatter than a pancake. This takes about 3 hours. I then reduce gas
pressure to 1psi from 3psi to hold the kiln at temperature for about an
hour in moderate reduction, .50 on the oxyprobe. Then I shut down and clam
the kiln and it cools for 36 hours before I crack it open. The refractoies
are k-26 Ifb's.
The nice thing about doing the Currie blends is that I don't have to adjust
my firing to produce a certain effect with a specific glaze. I find the
results on the tiles that fit my firing scheule. Not true in every single
case but it does work well most of the time.
Have a happy Christmas Ivor, Craig Martell in Oregon
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