Tracey Duivestein on sun 20 may 12
I am having an ongoing problem with glaze pinholes & after many trials &
tests it seems to be happening when I apply glaze over thick slip. In my
last kiln load I tried 3 types of clay with 15 different glazes with the
same results. Most test cylinders without the slip are pinhole free.
The slip is made from the same body as the thrown cylinders (using
borehole water & sieved through a 60 mesh sieve) & applied just after
turning. The cylinders are sponged prior to glazing, dipped into the
glaze, bisqued to Cone 04 & glaze fired to cone 6 in an electric kiln
(using the MC6G schedule with a downfire).
I have used different firing schedules, increased the bisque temperature
(from cone 06), mixed various glazes (boron frits & zinc) & used various
glaze thickness without any success.
Any suggestions or anything I am missing?
Many thanks
Tracey
Lee on sun 20 may 12
A more vitreous slip might help. My slip at con 10 and above is
Super White stoneware I buy dry by the bag. It is supposed to be a
cone 6 to 9 clay body, so is softer under my glazes than my clay body
is. It will melt the glaze above more than the clay body. And
works as a flashing slip without glaze in soda or wood fire.
You can also try wet sponging the slip area. It might simply be
more porous than the clay body itself.
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D9=
7that is, =3D
"The
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Lee on mon 21 may 12
Tracy,
Check this out below. The yunomi is (cover your eyes glaze
police!) intentionally pinholed and crawled on the outside, but where
I put the soft slip on the inside, perfectly smooth. The glaze is
Mino Shino, with no soda ash or clay.
Punchong is one of my main techniques, my area of expertise. All
my ware has slip on the inside and either slip or slip inlay on the
outside.
Something Ron never asks: do you see pinholing immediately
after glazing? If so, your slip is not bisqued enough for your
application. Sponging wet water on the outside may help.
http://shinoglaze.blogspot.com/2008/04/mino-shino-alumina-oxide-and-l=
=3D
ow-melt.html
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D9=
7that is, =3D
"The
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
ronroy@CA.INTER.NET on mon 21 may 12
Hi Tracey,
Sounds like the slip could be vitrifying too much - what is in bore
hole water? Are you sieving anything out of the slip - like grog?
RR
Quoting Tracey Duivestein :
> I am having an ongoing problem with glaze pinholes & after many trials &
> tests it seems to be happening when I apply glaze over thick slip. In my
> last kiln load I tried 3 types of clay with 15 different glazes with the
> same results. Most test cylinders without the slip are pinhole free.
>
> The slip is made from the same body as the thrown cylinders (using
> borehole water & sieved through a 60 mesh sieve) & applied just after
> turning. The cylinders are sponged prior to glazing, dipped into the
> glaze, bisqued to Cone 04 & glaze fired to cone 6 in an electric kiln
> (using the MC6G schedule with a downfire).
>
> I have used different firing schedules, increased the bisque temperature
> (from cone 06), mixed various glazes (boron frits & zinc) & used various
> glaze thickness without any success.
>
> Any suggestions or anything I am missing?
>
> Many thanks
> Tracey
>
ronroy@CA.INTER.NET on wed 23 may 12
It is true that I don't think that pinholes occur because of bubbles =3D20
in a glaze during application - I'd like to see the proof that they =3D20
are the same pits before and after melting.
Perhaps in a glaze that has not melted properly you can still see the =3D20
original scars left from glaze application.
By far the vast majority of pin holes are due to gasses generated =3D20
during a firing and the holes left not closing over.
Finding the real cause of pin holes leads to the ultimate solution of =3D20
the problem.
Of corse the opposite is also true if one wishes to get pinholes - the =3D2=
0
same knowledge can be used to get then as to eliminate them.
RR
Quoting Lee :
> Tracy,
>
> Check this out below. The yunomi is (cover your eyes glaze
> police!) intentionally pinholed and crawled on the outside, but where
> I put the soft slip on the inside, perfectly smooth. The glaze is
> Mino Shino, with no soda ash or clay.
>
> Punchong is one of my main techniques, my area of expertise. All
> my ware has slip on the inside and either slip or slip inlay on the
> outside.
>
> Something Ron never asks: do you see pinholing immediately
> after glazing? If so, your slip is not bisqued enough for your
> application. Sponging wet water on the outside may help.
>
> =3D20
> http://shinoglaze.blogspot.com/2008/04/mino-shino-alumina-oxide-and-low=
=3D
-melt.html
> --
> =3DC2=3DA0Lee Love in Minneapolis
> http://mingeisota.blogspot.com/
>
> =3DC2=3DA0"Ta tIr na n-=3DC3=3DB3g ar chul an tI=3DE2=3D80=3D94tIr dlainn=
trina ch=3DC3=3D
=3DA9ile"=3DE2=3D80=3D94that is, "The
> land of eternal youth is behind the house, a beautiful land fluent
> within itself." -- John O'Donohue
>
Lee on wed 23 may 12
On Wed, May 23, 2012 at 8:29 PM, wrote:
> Of corse the opposite is also true if one wishes to get pinholes - the sa=
=3D
me
> knowledge can be used to get then as to eliminate them.
A low bisque, or as tradtional in shino mogusa clay, a very high
alumina body, enhances pinholing. It has a base coat of Mino with
10% with regular mino over it. The clay body is high in alumina and
not vitrified.
Here is an example:
http://shinoglaze.blogspot.com/2009/07/mino-shino.html
Here is an example of the same clay, but only bisqued to 800*F. It
exhibits no pinholing, but much more glaze/body interaction.
http://shinoglaze.blogspot.com/2010/04/no-soda-ash-no-clay-shino.html
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D9=
7that is, =3D
"The
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Ben Morrison on thu 24 may 12
I've had pin holing from out-gassing of the clay body more than anything el=
=3D
se. My old college instructor liked to throw in some lowfire red clay for c=
=3D
olor, but at cone 10 it would often out-gas and cause some pitting and pin =
=3D
holing.=3DC2=3DA0=3D0A=3D0A-Ben=3D0A=3D0A=3D0A=3D0A________________________=
________=3D0A From=3D
: "ronroy@CA.INTER.NET" =3D0ATo: Clayart@LSV.CERAMICS.=
OR=3D
G =3D0ASent: Wednesday, May 23, 2012 6:29 PM=3D0ASubject: Re: Glaze pin-hol=
ing =3D
over slip=3D0A =3D0AIt is true that I don't think that pinholes occur becau=
se o=3D
f bubbles in a glaze during application - I'd like to see the proof that th=
=3D
ey are the same pits before and after melting.=3D0A=3D0APerhaps in a glaze =
that=3D
has not melted properly you can still see the original scars left from gla=
=3D
ze application.=3D0A=3D0ABy far the vast majority of pin holes are due to g=
asse=3D
s generated during a firing and the holes left not closing over.=3D0A=3D0AF=
indi=3D
ng the real cause of pin holes leads to the ultimate solution of the proble=
=3D
m.=3D0A=3D0AOf corse the opposite is also true if one wishes to get pinhole=
s - =3D
the same knowledge can be used to get then as to eliminate them.=3D0A=3D0AR=
R=3D0A=3D
=3D0A=3D0A=3D0AQuoting Lee :=3D0A=3D0A> Tracy,=3D0A=
> =3D0A>=3DC2=3DA0=3D
=3DC2=3DA0 Check this out below.=3DC2=3DA0 The yunomi is (cover your eyes=
glaze=3D
=3D0A> police!) intentionally pinholed and crawled on the outside, but wher=
e=3D
=3D0A> I put the soft slip on the inside, perfectly smooth.=3DC2=3DA0 The g=
laze i=3D
s=3D0A> Mino Shino, with no soda ash or clay.=3D0A> =3D0A>=3DC2=3DA0 =3DC2=
=3DA0 Punchong=3D
is one of my main techniques, my area of expertise.=3DC2=3DA0 All=3D0A> my=
ware =3D
has slip on the inside and either slip or slip inlay on the=3D0A> outside.=
=3D0A=3D
> =3D0A>=3DC2=3DA0 =3DC2=3DA0 =3DC2=3DA0 =3DC2=3DA0 =3DC2=3DA0 Something Ro=
n never asks:=3DC2=3DA0 d=3D
o you see pinholing immediately=3D0A> after glazing?=3DC2=3DA0 If so, your=
slip =3D
is not bisqued enough for your=3D0A> application.=3DC2=3DA0 Sponging wet w=
ater o=3D
n the outside may help.=3D0A> =3D0A>=3DC2=3DA0 =3DC2=3DA0 =3DC2=3DA0 http:=
//shinoglaze.blo=3D
gspot.com/2008/04/mino-shino-alumina-oxide-and-low-melt.html=3D0A> --=3D0A>=
=3DC2=3D
=3DA0Lee Love in Minneapolis=3D0A> http://mingeisota.blogspot.com/=3D0A> =
=3D0A> =3DC2=3D
=3DA0"Ta tIr na n-=3DC3=3DB3g ar chul an tI=3DE2=3D80=3D94tIr dlainn trina =
ch=3DC3=3DA9ile"=3D
=3DE2=3D80=3D94that is, "The=3D0A> land of eternal youth is behind the hous=
e, a bea=3D
utiful land fluent=3D0A> within itself." -- John O'Donohue=3D0A>
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