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NoSpam
October 26th 03, 02:48 AM
Why can't one put glaze on Greenware? I don't understand...
I think the glaze would just soke into the greenware and leave the color
The glaze is just a glass sealer. What would happend if one glazed
greenware?
Does the greenware shrink in the kiln? Can someone explain?




Thanks...

Dewitt
October 26th 03, 03:22 AM
On Sat, 25 Oct 2003 21:48:28 -0500, "NoSpam" > wrote:

>Why can't one put glaze on Greenware? I don't understand...
>I think the glaze would just soke into the greenware and leave the color
>The glaze is just a glass sealer. What would happend if one glazed
>greenware?
>Does the greenware shrink in the kiln? Can someone explain?

You can and some potters do. It's call raw firing. There are
definitely some advantages to bisqueing before glazing - it burns the
nasties out of the clay before the glaze firing and it makes the
pieces easier to glaze. Also, glazes intended for bisque work may not
work well on pieces that haven't been bisqued. Glazes for raw firing
typically have a high clay content.

deg

Monika Schleidt
October 26th 03, 07:59 AM
NoSpam wrote:

> Why can't one put glaze on Greenware? I don't understand...
> I think the glaze would just soke into the greenware and leave the color
> The glaze is just a glass sealer. What would happend if one glazed
> greenware?
> Does the greenware shrink in the kiln? Can someone explain?
>

Theoretically you can, but greenware is hard to handle, very fragile, and
the clay would soften as you dip it in the glaze. This is a problem
especially with thin pieces.
The glaze doesn't soak in, the water soaks in, leaving the glaze particles
on the surface, the same as in bisqued ware.
Yes, clay shrinks in drying, in bisque firing and in glazefiring. How much
it shrinks altogether depends on the clay you use.

Monika

--
Monika Schleidt

www.schleidt.org/mskeramik

Pierre Brayford
October 26th 03, 10:00 AM
Yes you can Glaze pots at the greenware stage - they can also be glazed at
the bone dry stage.

For a glaze to work on greenware it has to accomodate the shrinkage that
occurs as the clay dries, in practice this usually means having a glaze with
ball clay in it (30% is a rough guide). The glaze then has to be
re-formulated that is other ingredients adjusted so that the fired glaze has
the same proportion of the various oxides (not such a daunting task witha
glaze calculation program).
You may find recipes for suitable glazes, probably referred to as "slip
glazes".

If you then want to fire the pots in one go (once firing) the firing cycle
has to be adjusted so that it starts like a biscuit firing has about an hour
soak at 900 deg Celsius, and then continues like a glaze firing.

To glaze at the bone dry stage you may get away with using a glaze
formulated for biscuit if it has some clay in it or add about 5% bentonite
to a biscuit glaze (don't just add to the liquid glaze -either mix into dry
igredients or if you have to add to an already mixed glaze mix with a small
amount of the glaz and then sieve it into the glaze mix).

Dennis Parks wrote a book - can't remeber the exact title but something like
"Oil firing and Raw glazing"
Also Andrew Holden "The self reliant potter" published around 1980 has a
section on raw glazing
Iv' just rembered tha Fran Tristram has a book about Once firing publishe by
A&C Black.

Have your eyes started to glaze yet??

It isn't really as daunting as it sounds just have a go!
Good luck
"NoSpam" > wrote in message
news:[email protected]
> Why can't one put glaze on Greenware? I don't understand...
> I think the glaze would just soke into the greenware and leave the color
> The glaze is just a glass sealer. What would happend if one glazed
> greenware?
> Does the greenware shrink in the kiln? Can someone explain?
>
>
>
>
> Thanks...
>
>

NoSpam
October 26th 03, 12:46 PM
Thanks for the info.
No.. I have not yet put any glaze on greenware...

I was just thinking about it and I did not understand "why not"...

I think, I will try "slip" type first...

Thank again....


"NoSpam" > wrote in message
news:[email protected]
> Why can't one put glaze on Greenware? I don't understand...
> I think the glaze would just soke into the greenware and leave the color
> The glaze is just a glass sealer. What would happend if one glazed
> greenware?
> Does the greenware shrink in the kiln? Can someone explain?
>
>
>
>
> Thanks...
>
>

Amber
October 26th 03, 03:14 PM
The glaze you would want to use is called under glaze. You can put this
glaze on either green ware or bisked ware. But if you put the under glaze on
while it's still green you would than want to put a clear coat on.
My instructor showed us an example of what happens when he put a glossy
glaze on a green ware pot. It ran down the side of the and left a ring at
the bottom because the glazes had nothing to stick to.
A.G.

"NoSpam" > wrote in message
news:[email protected]
> Thanks for the info.
> No.. I have not yet put any glaze on greenware...
>
> I was just thinking about it and I did not understand "why not"...
>
> I think, I will try "slip" type first...
>
> Thank again....
>
>
> "NoSpam" > wrote in message
> news:[email protected]
> > Why can't one put glaze on Greenware? I don't understand...
> > I think the glaze would just soke into the greenware and leave the color
> > The glaze is just a glass sealer. What would happend if one glazed
> > greenware?
> > Does the greenware shrink in the kiln? Can someone explain?
> >
> >
> >
> >
> > Thanks...
> >
> >
>
>
>

Uncle John
October 26th 03, 06:47 PM
"Amber" > wrote in
:

> The glaze you would want to use is called under glaze. You can put
> this
> glaze on either green ware or bisked ware. But if you put the under
> glaze on while it's still green you would than want to put a clear
> coat on.
> My instructor showed us an example of what happens when he put a
> glossy
> glaze on a green ware pot. It ran down the side of the and left a
> ring at the bottom because the glazes had nothing to stick to.
> A.G.
>
> "NoSpam" > wrote in message
> news:[email protected]
>> Thanks for the info.
>> No.. I have not yet put any glaze on greenware...
>>
>> I was just thinking about it and I did not understand "why not"...
>>
>> I think, I will try "slip" type first...
>>
>> Thank again....
>>
>>
>> "NoSpam" > wrote in message
>> news:[email protected]
>> > Why can't one put glaze on Greenware? I don't understand...
>> > I think the glaze would just soke into the greenware and leave the
>> > color The glaze is just a glass sealer. What would happend if one
>> > glazed greenware?
>> > Does the greenware shrink in the kiln? Can someone explain?
>> >
>> >
>> >
>> >
>> > Thanks...
>> >
>> >
>>

You may find this hard to believe but once upon a time all pottery was
green glazed.

As far as I am aware bisquet firing is a recent western tradition and was
only introduced to England in the 17th century from France as an
industrial process. Even now days it is only industrial factories, studio
potters and teachers of ceramics and their pupils who bisque fire.

I would imagine that the majority of readers of this group have never
tried it out.

Glaze formulation for green ware is no more diffficult than formulating a
well fitted glaze for low or high fired bisque. The main thing to know is
the shrinkage of the clay from green to the final fired temperature. This
can be done by experimentation with the clay body.

Of course you need to design products that are suitable for the process.

Cheers

John W

annemarie
October 27th 03, 03:21 AM
"Amber" > wrote in message
...
> The glaze you would want to use is called under glaze. You can put
this
> glaze on either green ware or bisked ware. But if you put the under glaze
on
> while it's still green you would than want to put a clear coat on.
> My instructor showed us an example of what happens when he put a
glossy
> glaze on a green ware pot. It ran down the side of the and left a ring at
> the bottom because the glazes had nothing to stick to.
> A.G.
>
No underglaze is a different thing. You can glaze greenware, or unbisqued
pottery at the leather hard stage (more difficult because of drying
shrinkage) or at the bone dry stage. Glazes mostly have to specifically
formulated for "once fired" work. It has dissadvantages, application of the
glaze can be done with spraying, painting, or very carefully dipping but you
run the risk of the pottery getting too wet and just falling to bits, or
even falling to bits into the bucket of glaze, and thus also ruining your
glaze. Bisquing also removes impurities that can cause pinwholing and other
problems.
Underglaze are colourants that go under a glaze, best IMO applied to dry
unfired work. It is then bisqued and a clear glaze applied and fired again.
If you underglaze bisqued ware you often have to refire before glazing to
burn off gums etc used to make underglaze flow well, but which are inclined
to resist the glaze a little.
Yes John I have tired once fired work, its fun :o)
A

Jan Clauson
October 30th 03, 11:33 PM
NoSpam wrote:

> Why can't one put glaze on Greenware? I don't understand...
> I think the glaze would just soke into the greenware and leave the color
> The glaze is just a glass sealer. What would happend if one glazed
> greenware?
> Does the greenware shrink in the kiln? Can someone explain?
>
>
>
>
> Thanks...
>
>
You can put glaze on greenware. I read of a potter who never bisqued
(he was firing low fire). So, I gave it a whirl. The glaze matured
properly and stayed on the pots. However, the reds turned either green
or went clear and the coppers turned black. I now have an off-white
apple that I did for one of the testers and my Armegeden piece which was
supposed to be oozing blood out of a copper body, is oozing green stuff
out of a black body instead. Considering the piece, I like my
accidental result better than the one I had planned.

Jan C.

NoSpam
October 31st 03, 03:03 AM
"Jan Clauson" > wrote in message
ink.net...
> NoSpam wrote:
>
> > Why can't one put glaze on Greenware? I don't understand...
> > I think the glaze would just soke into the greenware and leave the color
> > The glaze is just a glass sealer. What would happend if one glazed
> > greenware?
> > Does the greenware shrink in the kiln? Can someone explain?
> >
> >
> >
> >
> > Thanks...
> >
> >
> You can put glaze on greenware. I read of a potter who never bisqued
> (he was firing low fire). So, I gave it a whirl. The glaze matured
> properly and stayed on the pots. However, the reds turned either green
> or went clear and the coppers turned black. I now have an off-white
> apple that I did for one of the testers and my Armegeden piece which was
> supposed to be oozing blood out of a copper body, is oozing green stuff
> out of a black body instead. Considering the piece, I like my
> accidental result better than the one I had planned.
>
> Jan C.
>

What type of "glaze"?

Jan Clauson
October 31st 03, 06:48 PM
Right now, all my stuff is packed ready to move next week. I don't
remember the brand or the color designator, but I used commercially
prepared low-fire glazes for this experiment. I used the same glazes on
other test pieces that had been bisqued and the colors were as
advertised. If you need, when I get my studio upacked (first thing,
before even my kitchen gets unpacked), I'll look up the specifics and
get back to you.

Jan C.

NoSpam
October 31st 03, 11:16 PM
No that is fine...
I just wanted to know if it was a commercial type glase...
I will try it this weekend...

"Jan Clauson" > wrote in message
link.net...
>
> Right now, all my stuff is packed ready to move next week. I don't
> remember the brand or the color designator, but I used commercially
> prepared low-fire glazes for this experiment. I used the same glazes on
> other test pieces that had been bisqued and the colors were as
> advertised. If you need, when I get my studio upacked (first thing,
> before even my kitchen gets unpacked), I'll look up the specifics and
> get back to you.
>
> Jan C.
>

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