Marjorie Beynon on mon 23 apr 01
Good Morning Tom: I have been thinking about your reply to my query about
shino glazed durability.
Part of my concern is the shino is a stiff/matt glaze under that glorius
surface and if a teapot, for example, was used on a regular basis and the
body was not tight and the glaze crazed ,the moisture would swell the pot
and you end up with a pot that oozes tea and has lost its integrity/strength
and would sound like a cardboard box instead of a pot if you tapped it.
Therefore my questions about how tight a body should be and if a liner glaze
would be a good choice. Which leads to the question - How much of a
difference in expansion of glazes can be used together on one pot. Insight
8plus on outside - Insight 6.5 - 7.0 on the inside ? Yes, I plan to test
all this but was hoping someone could steer me in the right direction so I
do not wander off track too far. MarjB
Liz Willoughby on mon 23 apr 01
Dear Marj,
Just thought that I would add a little here regarding shino used on teapots.
I've made a lot of teapots using shino, and have used one or two of
them often in my kitchen over the past few years. It is a shino with
high soda ash, Malcolms #2 in fact, and I replaced half the EPK with
alumina. Porcelain fired to cone 10/11 R, and it is probably close
to 0 absorbancy. Never had any problems. I almost always test my
teapots too, after firing, with boiling water, with no heat up at
with warm water.
There are some crazing lines inside the teapots that I use, those
lines are dark brown from the tea, but it doesn't really concern me
if the clay is or almost, vitreous.
I might be concerned using a cone 6 clay that usually isn't vitreous
after glaze firing.
Another point is that if you used a liner glaze when glazing the
outside with a carbon trap shino glaze, you are not going to get
great results with the carbon trapping because the salts on the
inside travel through the clay body to deposit more salts. Also
every shino is different, much depends on the recipe. Shino is a
glaze type (Ha! Maple leaf shino is not a bad name for a Canuck Shino
Mel), so maybe when we talk about it we should specify.
Love all this shino stuff.
Liz
>
>
>Part of my concern is the shino is a stiff/matt glaze under that glorius
>surface and if a teapot, for example, was used on a regular basis and the
>body was not tight and the glaze crazed ,the moisture would swell the pot
>and you end up with a pot that oozes tea and has lost its integrity/strength
>and would sound like a cardboard box instead of a pot if you tapped it.
>
>Therefore my questions about how tight a body should be and if a liner glaze
>would be a good choice. Which leads to the question - How much of a
>difference in expansion of glazes can be used together on one pot. Insight
>8plus on outside - Insight 6.5 - 7.0 on the inside ? Yes, I plan to test
>all this but was hoping someone could steer me in the right direction so I
>do not wander off track too far. MarjB
>
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Liz Willoughby
RR 1
2903 Shelter Valley Rd.
Grafton, On.
Canada
K0K 2G0
e-mail lizwill@phc.igs.net
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