Janine Roubik on fri 22 sep 06
Hey everybody,
I have 2 glaze questions for all y'all...
The first is Penn State Carbon Trap Shino.(Here's the recipe, because I
know if I don't write it here someone will ask...)
Neph Sye 14.6
F4 feld 34
Spodumene 29
Kaolin 9.7
Ball clay 4.9
Soda ash 7.8
Mixed to 140 sp. gr. From John Britt's book.
Turned out very dry,(Too thin? I single dipped and held for 2
mississippi's) real nice peachy-oragey-whitey color, but no carbon
trapping and where the bubbles were from the glaze being mixed and frothy
stayed in the glaze! From what I remembered about shinos I used in
school those kinda melted out in the firing and you didn't need to worry
about them too much...I wish there was someway I could post pictures for
everyone - I know I can do it in my own e-mail, so write me off list if
you want a photo emailed to you. I bisque to about c/05 (I say about
because I've found a bottom switch is bad..another problem...uuuuhhh)
And...here's the rub...unfortunately I don't control the kiln. This was
overfired to probably cone 13-14 because kiln owner got drunk.(oh - this
post is going to be in cyberspace forever....hmmm too bad)He says he
starts reducing at about c/010 and reduces heavily throughout. This shino
was not allowed time to dry and the soda to migrate, which is all my
fault - trying to rush things to get in the firing. But I thougt I'd get a
teeny tiny bit at least with that much soda ash.(Funny incidental - I
mixed the soda ash in a bucket with hot water to get it dissolved and had
the good sense to not stir it with my hand - but then I noticed a little
peice of sponge from when I was cleaning the bucket and reached in there
to grab it! DOH! I don't reccommend that!)
Also, Tom Buck's celadon (revisited)
custer feld 30
silica 24
whiting 25
grolleg 21
Black Iron Oxide 1
sp. gr. 159 last time I think.
For those of you who were paying attention to the last thread on this I
was trying to find a way to sub the Black Iron for yellow or red...but
then it turned out I needed a bunch of other stuff from the clay store, so
just got the black iron while I was there. Sorry for being a clayart
talent waster!
I'm currently using ART's 119 white stoneware "danish porcelain" I
absolutley love the color, but am getting crazing. John B. suggested some
in the Roy/Hesselberth camp may have a solution for this. I guess I don't
know how much crazing is normal for a celadon and acceptable for
functional pieces. It sure is purty, though. Again, I'd e-mail you a
picture if anyone would like.
Thanks again in advance,
Janine Roubik
Dave Finkelnburg on fri 22 sep 06
Janine,
--- Janine Roubik wrote:
> Hey everybody,
> I have 2 glaze questions for all y'all...
> The first is Penn State Carbon Trap Shino.(Here's
> the recipe, because I
> know if I don't write it here someone will ask...)
> Neph Sye 14.6
> F4 feld 34
> Spodumene 29
> Kaolin 9.7
> Ball clay 4.9
> Soda ash 7.8
> Mixed to 140 sp. gr. From John Britt's book.
>
> Turned out very dry,(Too thin? I single dipped and
> held for 2
> mississippi's) real nice peachy-oragey-whitey color,
> but no carbon
> trapping and where the bubbles were from the glaze
> being mixed and frothy
> stayed in the glaze! From what I remembered about
> shinos I used in
> school those kinda melted out in the firing and you
> didn't need to worry
> about them too much...I wish there was someway I
> could post pictures for
> everyone - I know I can do it in my own e-mail, so
> write me off list if
> you want a photo emailed to you. I bisque to about
> c/05 (I say about
> because I've found a bottom switch is bad..another
> problem...uuuuhhh)
> And...here's the rub...unfortunately I don't control
> the kiln. This was
> overfired to probably cone 13-14 because kiln owner
> got drunk.(oh - this
> post is going to be in cyberspace forever....hmmm
> too bad)He says he
> starts reducing at about c/010 and reduces heavily
> throughout. This shino
> was not allowed time to dry and the soda to migrate,
> which is all my
> fault - trying to rush things to get in the firing.
> But I thougt I'd get a
> teeny tiny bit at least with that much soda
> ash.(Funny incidental - I
> mixed the soda ash in a bucket with hot water to get
> it dissolved and had
> the good sense to not stir it with my hand - but
> then I noticed a little
> peice of sponge from when I was cleaning the bucket
> and reached in there
> to grab it! DOH! I don't reccommend that!)
>
> Also, Tom Buck's celadon (revisited)
> custer feld 30
> silica 24
> whiting 25
> grolleg 21
> Black Iron Oxide 1
> sp. gr. 159 last time I think.
> For those of you who were paying attention to the
> last thread on this I
> was trying to find a way to sub the Black Iron for
> yellow or red...but
> then it turned out I needed a bunch of other stuff
> from the clay store, so
> just got the black iron while I was there. Sorry
> for being a clayart
> talent waster!
> I'm currently using ART's 119 white stoneware
> "danish porcelain" I
> absolutley love the color, but am getting crazing.
> John B. suggested some
> in the Roy/Hesselberth camp may have a solution for
> this. I guess I don't
> know how much crazing is normal for a celadon and
> acceptable for
> functional pieces. It sure is purty, though.
> Again, I'd e-mail you a
> picture if anyone would like.
> Thanks again in advance,
> Janine Roubik
>
>
______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change
> your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be
> reached at melpots@pclink.com.
>
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Dave Finkelnburg on fri 22 sep 06
Janine,
How much crazing is OK for you is a personal
choice, period...THERE IS NO "NORMAL" FOR
CRAZING...for celdons or any other glaze. You can
reduce crazing, within limits, by using materials that
don't shrink as much. Adding silica (quartz) or clay
reduces shrinkage. If you add too much, though, the
glaze won't melt at your firing temperature.
Every clay body has a somewhat different
shrinkage. Porcelains, in general, don't shrink as
much as stoneware bodies. The more vitrified a body
is the higher its contraction will be on cooling.
Thus, underfired bodies are worse for causing crazing.
The bottom line for you, and anyone else concerned
about this, is crazing is a function of a particular
clay body/glaze/firing combination. IF you want to
control crazing you have to recognize all three have
an effect and you need to control them.
PLEASE don't come after me for mentioning control
and crazing in the same post. I DO NOT fear crazing,
dislike it, discriminate against it, etc, etc. It can
look great. However, as a practical matter, crazed
pots are weaker--only one-fourth to one-fifth as
strong as uncrazed pots!
If you want to reduce crazing you need to test
recipe changes that move you to less high expansion
fluxes, (for example, use a higher K, lower Na
feldspar), more Si, Al, possibly less alkali fluxes,
more Ca... This is where glaze calc is helpful. Or,
a Currie grid type approach is a highly organized way
to explore the possibilities.
Good glazing!
Dave Finkelnburg, thinking the only way at that
temperature your Shino didn't melt is it was on way
too thin, as you suggest. You might want to increase
glaze density (say 1.45) to get a thicker coat, and
double dip. Also, pull the piece slowly from the
tub...too fast literally washes the glaze off the pot!
--- Janine Roubik wrote:
> The first is Penn State Carbon Trap Shino> Turned
out very dry
> Also, Tom Buck's celadon (revisited)
>> absolutley love the color, but am getting crazing.
I guess I don't
> know how much crazing is normal for a celadon and
> acceptable for
> functional pieces.
__________________________________________________
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http://mail.yahoo.com
Janine Roubik on fri 22 sep 06
Oooops - Hey Dave - nothing came through on the last post. Please re-post if you have time.
Dave Finkelnburg wrote: Janine,
--- Janine Roubik wrote:
> Hey everybody,
> I have 2 glaze questions for all y'all...
> The first is Penn State Carbon Trap Shino.(Here's
> the recipe, because I
> know if I don't write it here someone will ask...)
> Neph Sye 14.6
> F4 feld 34
> Spodumene 29
> Kaolin 9.7
> Ball clay 4.9
> Soda ash 7.8
> Mixed to 140 sp. gr. From John Britt's book.
>
> Turned out very dry,(Too thin? I single dipped and
> held for 2
> mississippi's) real nice peachy-oragey-whitey color,
> but no carbon
> trapping and where the bubbles were from the glaze
> being mixed and frothy
> stayed in the glaze! From what I remembered about
> shinos I used in
> school those kinda melted out in the firing and you
> didn't need to worry
> about them too much...I wish there was someway I
> could post pictures for
> everyone - I know I can do it in my own e-mail, so
> write me off list if
> you want a photo emailed to you. I bisque to about
> c/05 (I say about
> because I've found a bottom switch is bad..another
> problem...uuuuhhh)
> And...here's the rub...unfortunately I don't control
> the kiln. This was
> overfired to probably cone 13-14 because kiln owner
> got drunk.(oh - this
> post is going to be in cyberspace forever....hmmm
> too bad)He says he
> starts reducing at about c/010 and reduces heavily
> throughout. This shino
> was not allowed time to dry and the soda to migrate,
> which is all my
> fault - trying to rush things to get in the firing.
> But I thougt I'd get a
> teeny tiny bit at least with that much soda
> ash.(Funny incidental - I
> mixed the soda ash in a bucket with hot water to get
> it dissolved and had
> the good sense to not stir it with my hand - but
> then I noticed a little
> peice of sponge from when I was cleaning the bucket
> and reached in there
> to grab it! DOH! I don't reccommend that!)
>
> Also, Tom Buck's celadon (revisited)
> custer feld 30
> silica 24
> whiting 25
> grolleg 21
> Black Iron Oxide 1
> sp. gr. 159 last time I think.
> For those of you who were paying attention to the
> last thread on this I
> was trying to find a way to sub the Black Iron for
> yellow or red...but
> then it turned out I needed a bunch of other stuff
> from the clay store, so
> just got the black iron while I was there. Sorry
> for being a clayart
> talent waster!
> I'm currently using ART's 119 white stoneware
> "danish porcelain" I
> absolutley love the color, but am getting crazing.
> John B. suggested some
> in the Roy/Hesselberth camp may have a solution for
> this. I guess I don't
> know how much crazing is normal for a celadon and
> acceptable for
> functional pieces. It sure is purty, though.
> Again, I'd e-mail you a
> picture if anyone would like.
> Thanks again in advance,
> Janine Roubik
>
>
______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change
> your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be
> reached at melpots@pclink.com.
>
__________________________________________________
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Tired of spam? Yahoo! Mail has the best spam protection around
http://mail.yahoo.com
______________________________________________________________________________
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Patrick Green on mon 25 sep 06
I wouldn't call myself a Guru or anythign but I will throw in my two pennys and you can take my advise with a grain or salt. I didn't catch you first post so I f I ask something you explained there I am sorry.
As per the celadon, how quickly is it cooling? It has been my eexperienc ethat crazing, particularly that sort where you have lots of little spots could be from it cooling to fast down from temp, (example: dropping 300 -400 degrees each hour the first hours or so) Also have you done a shrinkage absortion on the specific clay body you are using? Don't get me wrong they corps try and make the clay as homogenious as possible but we are talking earth here not some white coated lab there are gonna be impurities.
As for the Shino, where was it in the kiln? and how hard was the reduction? Again speaking from experience, I have noted that most kilns how an area in them that always seems to get poor carbon traping,( usually the bottom middle to front of the kiln, jutting upward in a sort of cone. another thing about reduction is it really must be started fairly earliy in the firing as should (in my option be carried throw tell the end).
well there you go, some sage advice from a true Soph-more ( wise fool)
Patrick Andrew Green
Janine Roubik wrote: Sorry,
The website is www.roubikpottery.com
They'll be on the main page towards the bottom.
Janine, feeling not so computer savvy.
______________________________________________________________________________
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You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
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Janine Roubik on mon 25 sep 06
Thanks for the help, Dave.
I see some people have blog pages where they can put up pictures, like I was hoping to do with these. How do you do that and what is a good site to use?
For now I will put them on my website which is under construction. I'll just put them on the main page, since it's not really done yet.
Janine
Dave Finkelnburg wrote:
Janine,
How much crazing is OK for you is a personal
choice, period...THERE IS NO "NORMAL" FOR
CRAZING...for celdons or any other glaze. You can
reduce crazing, within limits, by using materials that
don't shrink as much. Adding silica (quartz) or clay
reduces shrinkage. If you add too much, though, the
glaze won't melt at your firing temperature.
Every clay body has a somewhat different
shrinkage. Porcelains, in general, don't shrink as
much as stoneware bodies. The more vitrified a body
is the higher its contraction will be on cooling.
Thus, underfired bodies are worse for causing crazing.
The bottom line for you, and anyone else concerned
about this, is crazing is a function of a particular
clay body/glaze/firing combination. IF you want to
control crazing you have to recognize all three have
an effect and you need to control them.
PLEASE don't come after me for mentioning control
and crazing in the same post. I DO NOT fear crazing,
dislike it, discriminate against it, etc, etc. It can
look great. However, as a practical matter, crazed
pots are weaker--only one-fourth to one-fifth as
strong as uncrazed pots!
If you want to reduce crazing you need to test
recipe changes that move you to less high expansion
fluxes, (for example, use a higher K, lower Na
feldspar), more Si, Al, possibly less alkali fluxes,
more Ca... This is where glaze calc is helpful. Or,
a Currie grid type approach is a highly organized way
to explore the possibilities.
Good glazing!
Dave Finkelnburg, thinking the only way at that
temperature your Shino didn't melt is it was on way
too thin, as you suggest. You might want to increase
glaze density (say 1.45) to get a thicker coat, and
double dip. Also, pull the piece slowly from the
tub...too fast literally washes the glaze off the pot!
--- Janine Roubik wrote:
> The first is Penn State Carbon Trap Shino> Turned
out very dry
> Also, Tom Buck's celadon (revisited)
>> absolutley love the color, but am getting crazing.
I guess I don't
> know how much crazing is normal for a celadon and
> acceptable for
> functional pieces.
__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
http://mail.yahoo.com
______________________________________________________________________________
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Janine Roubik on mon 25 sep 06
Sorry,
The website is www.roubikpottery.com
They'll be on the main page towards the bottom.
Janine, feeling not so computer savvy.
Janine Roubik on thu 28 sep 06
Hey Patrick,
Thanks for the toughts. Unfortunately, I have no control over the kiln! Until I win the lottery that is....(HA!)
The original post was last week friday maybe (?) If you wanted to look it up Well, now I have a bunch of tests to try...
Thanks again all,
Janine
Patrick Green wrote:
I wouldn't call myself a Guru or anythign but I will throw in my two pennys and you can take my advise with a grain or salt. I didn't catch you first post so I f I ask something you explained there I am sorry.
As per the celadon, how quickly is it cooling? It has been my eexperienc ethat crazing, particularly that sort where you have lots of little spots could be from it cooling to fast down from temp, (example: dropping 300 -400 degrees each hour the first hours or so) Also have you done a shrinkage absortion on the specific clay body you are using? Don't get me wrong they corps try and make the clay as homogenious as possible but we are talking earth here not some white coated lab there are gonna be impurities.
As for the Shino, where was it in the kiln? and how hard was the reduction? Again speaking from experience, I have noted that most kilns how an area in them that always seems to get poor carbon traping,( usually the bottom middle to front of the kiln, jutting upward in a sort of cone. another thing about reduction is it really must be started fairly earliy in the firing as should (in my option be carried throw tell the end).
well there you go, some sage advice from a true Soph-more ( wise fool)
Patrick Andrew Green
Janine Roubik wrote: Sorry,
The website is www.roubikpottery.com
They'll be on the main page towards the bottom.
Janine, feeling not so computer savvy.
______________________________________________________________________________
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
---------------------------------
How low will we go? Check out Yahoo! Messenger’s low PC-to-Phone call rates.
______________________________________________________________________________
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
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