Curtis Nelson on wed 21 mar 07
This is a question about pouring liner glaze in pots for ^6 electric firing.=
I made its specific gravity 1.56. Just before pouring the glaze in and out o=
f the pot
real fast, the pot=92s interior was wiped out with a slightly damp sponge to=
clean off any
surface dust. The bisque firing had been ^08.
The water in the glaze was sucked up by the bisqued clay so quickly that, up=
on
pouring out, glaze rivulets were frozen in place, leaving subtantially thick=
lines of
dried glaze. And the rims were left unacceptably bumpy and, in places, bare =
of glaze
that had to be filled in with finger dabs. This can=92t be the way to do thi=
ngs. Otherwise,
over all, the glaze is a good thickness, maybe three playing cards thick.
The glaze has no hardener in it like cmc, so it=92s really powdery. I gently=
rubbed down
the dry lumpy rivulets and bumps on the rim with my fingers until they were
somewhat gone. But in the deeper vases, I can=92t reach in very far. I=92ll =
see the result of
those untouched rivulets after the firing, I hope they just melt and disappe=
ar.
Anyway, before I pour liners again, I=92d like opinions on whether this prob=
lem of glaze
freezing too quickly could be addressed by:
1) Wiping out the pot interiors with a much wetter sponge so the bisque does=
n=92t suck
up the glaze water so fast, allowing the glaze to run out before being froze=
n in place
from lack of water in it.
2) Diluting the glaze. But then the specific gravity would drop, and glaze c=
overage
would be less than ideal thickness.
3) Adding something to the glaze that I don=92t know about?
4) Bisque firing to a higher temperature than ^08?
Metalic Black Glaze
Gerstley 10.75
Whiting 5.48
Feldspar 78.86 (I used F-4)
Kaolin 4.91 (I used EPK)
Add:
Cobalt Ox 2.07 (I used 2% cobalt carb)
Copper carb 4.14
Manganese diox 4.14
And by the way, I=92ve heard of adding cmc to a glaze to give it a hard, or =
at least a
less powdery surface. How much should be added, if this is a good thing to d=
o at all?
And if you create a hard glaze surface, wouldn=92t that inhibit rubbing down=
rivulets
and lumps, if you could rub them down at all?
Best -
Curt Nelson
Asheville, NC
Judy Rohrbaugh on thu 22 mar 07
Curtis,
You could try washing your pots- a quick dunk into a pail full of water is good,
then let them dry for x hours before you glaze.
Whenever I pour into a pot, the glaze is quite thin, but I use most of my glazes that way,
inside and out.
I bisque to 08.
Judy Rohrbaugh
Fine Art Stoneware
Ohio, USA
Curtis Nelson wrote:
...The water in the glaze was sucked up by the bisqued clay so quickly that, upon
pouring out, glaze rivulets were frozen in place, leaving subtantially thick lines of
dried glaze. And the rims were left unacceptably bumpy and, in places, bare of glaze
that had to be filled in with finger dabs.......
Eric Hansen on thu 22 mar 07
Curt: I pour liner glazes and yes some glaze/clay body
combinations are more squirrely than others. So the
question is did you mix your own clay too? You'll have
to explore the parameters as to where the body it too
absorbent. Normally I get the bisque as dry as
possible but there are other practices such as
moistening the bisque which I cannot authoratativly
comment on. Also I work really fast and the forms have
this way of working in mind - thick glazes in and out
fast. Also I fill them to the brim and then pour them
out. The other issue is that there can be a mechanical
reaction in the glaze. Sometimes thorough blunging is
not enough. Once I even had a glaze that foamed (!)
Also my professor once asked "what is wrong with
bisquing to 06?" hmm.
Also what is this business about manganese in a liner
glaze? Is that really cool? Gurus?
H A M B O N E
eric hansen
--- Curtis Nelson wrote:
> This is a question about pouring liner glaze in pots
> for ^6 electric firing.
>
> I made its specific gravity 1.56. Just before
> pouring the glaze in and out of the pot
> real fast, the pot’s interior was wiped out with a
> slightly damp sponge to clean off any
> surface dust. The bisque firing had been ^08.
>
> The water in the glaze was sucked up by the bisqued
> clay so quickly that, upon
> pouring out, glaze rivulets were frozen in place,
> leaving subtantially thick lines of
> dried glaze. And the rims were left unacceptably
> bumpy and, in places, bare of glaze
> that had to be filled in with finger dabs. This
> can’t be the way to do things. Otherwise,
> over all, the glaze is a good thickness, maybe three
> playing cards thick.
>
> The glaze has no hardener in it like cmc, so it’s
> really powdery. I gently rubbed down
> the dry lumpy rivulets and bumps on the rim with my
> fingers until they were
> somewhat gone. But in the deeper vases, I can’t
> reach in very far. I’ll see the result of
> those untouched rivulets after the firing, I hope
> they just melt and disappear.
>
> Anyway, before I pour liners again, I’d like
> opinions on whether this problem of glaze
> freezing too quickly could be addressed by:
>
> 1) Wiping out the pot interiors with a much wetter
> sponge so the bisque doesn’t suck
> up the glaze water so fast, allowing the glaze to
> run out before being frozen in place
> from lack of water in it.
>
> 2) Diluting the glaze. But then the specific gravity
> would drop, and glaze coverage
> would be less than ideal thickness.
>
> 3) Adding something to the glaze that I don’t know
> about?
>
> 4) Bisque firing to a higher temperature than ^08?
>
> Metalic Black Glaze
>
> Gerstley 10.75
> Whiting 5.48
> Feldspar 78.86 (I used F-4)
> Kaolin 4.91 (I used EPK)
>
> Add:
>
> Cobalt Ox 2.07 (I used 2% cobalt
> carb)
> Copper carb 4.14
> Manganese diox 4.14
>
> And by the way, I’ve heard of adding cmc to a glaze
> to give it a hard, or at least a
> less powdery surface. How much should be added, if
> this is a good thing to do at all?
> And if you create a hard glaze surface, wouldn’t
> that inhibit rubbing down rivulets
> and lumps, if you could rub them down at all?
>
> Best -
>
> Curt Nelson
> Asheville, NC
>
>
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