Ababi on thu 7 aug 03
Because Ellie have sent the recipe to the list I will add here my answer
to Ellie. Out of the "intermediate - humble experience" I have with clay
-glaze with crystal glazes.
"intermediate - humble experience", because I understand more than I can
explain and I can explain more than I understand!
Crystal glaze is a completely abnormal, it is hard to judge it as a
glaze. Here is the analysis of Ellie's glaze:
Seger Weight%
KNO 0.29 9.68%
CaO 0.12 3.46%
ZnO 0.59 24.86%
Al2O3 0.04 2.23%
B2O3 0.04 1.42%
SiO2 1.72 53.30%
TiO2 0.12 5.06%
K2O 0.03 1.27%
Na2O 0.26 8.41%
Al:Si 40.53=09
Expan. 9.62 =09
Sometimes, adding a lot of flux colorants like copper manganese or
cobalt will add flux.
This is not the case. I say it after trying it in Matrix.
So what could happen?
Was the claybody changed without a notice? Hard to believe - Would they
do it to you without a notice?
Ellie fires to ^10 and I fire to ^6
The base I use (my base) the analysis is not definitely sure as I
adopted the analysis of the red clay from a similar product.
Seger Weight%
KNO 0.36 13.28%
CaO 0.09 2.89%
MgO 0.00 0.11%
ZnO 0.50 23.66%
Li2O 0.05 0.83%
Al2O3 0.05 3.24%
SiO2 1.59 55.98%
K2O 0.01 0.49%
Na2O 0.35 12.79%
Al:Si 29.27=09
Expan. 10.47=09
Yet very similar. In some cases, my glaze on the same claybody craze
sometimes in others not.=20
The more interesting fact is the way the claybody effects the crazing.
The VC raku claybody I have since rakuing was excellent without crazing.
The problem is that I cannot remember if I used EPK or French kaolin and
Nital or French talc C-2. The last talc has 10% alumina - I will have to
repeat the tests.
A claybody Tom Buck had formulated for me when I could not buy plastic
kaolin.
The regular glazes are crazing on Tom's claybody crystals are not. Here
too I do not remember If I changed it since I have plastic kaolin - Tom
made the ball clay AK main and the Kaolin CC31 second I might of change
it.=20
Both recipe containing extra alumina.
Perhaps adding alumina to the claybody will help to avoid crazing. This
is about the "intermediate - humble experience". Perhaps you Ron or you
Ivor can put together my understanding to kind of "rules".
The next step was to offer a cure.
The 3110 has a lot of sodium with very high expansion.
You can remove some of it and add tiny amounts of lithium carbonate -
which is a strong flux and has a very low expansion.
Another advise was to try and increase slightly - slightly the alumina
by adding small amounts of kaolin ( calcined of course(
I shall add here the letter I have sent to Ellie without removing parts.
When you read it feel free to skip parts you have read already.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ELLIE'S BASE CRYSTAL
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
=20
Cone 8 1263 deg.C. - =20
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
=20
frit 3110 54.00
zinc oxide calcined 24.60
Flint 14.90
Titanium Dioxide 4.00
EPK 0.50
Manganese Dioxide 4.00
Nickel Oxide 1.00
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
=20
Seger Weight%
KNO 0.259 9.28%
CaO 0.107 3.32%
ZnO 0.530 23.83%
Al2O3 0.038 2.14%
B2O3 0.035 1.36%
SiO2 1.539 51.09%
TiO2 0.110 4.85%
K2O 0.023 1.22%
Na2O 0.235 8.06%
NiO 0.0235 0.97%
MnO 0.0807 3.16%
Al:Si 40.53 =20
Expan. 9.38 =20
ST 338.70 =20
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Here is my suggestion: the recipe ends in 98.
Make four batches of 98 grams.
To the first batch add 0.5 grams lithium carbonate. To the second 1 up
to the third 1.5 and to the fourth 2%. If it does not help or the glaze
is too runny decrease the frit =96 but in higher amounts.2-4-6 and keep
the lithium. You can also try to add some alumina perhaps 1-4 calcined
kaolin. I give you here a recipe for a claybody that Tom Buck had
created for me - That time I could not buy plastic kaolin. Therefore he
used more ball clay and less kaolin. I cannot remember exactly how I
made it the last time ( I do have plastic kaolin this days. I think that
the very high alumina keeps it from crazing. This claybody does not
crease in crystals but crease in any other glaze! ( I could not buy
molochite that time too(
ABABI'S ^6 PORCELIANOUS BY TOM BUCK
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
=20
Cone 6 1222 deg.C. - =20
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
=20
ball clay (My AK) 48.00 you can change the places of the kaolin
and the=20
kaolin 33.00
Nepheline Syenite 14.00
Alumina Hydrate 5.00 you can use alumina oxide
Bentonite 2.00
"""""""""""""""""""""""""""""""""""""""""""""
Here is claybody HATES titanium!
Again I do not remember exactly the raw material. Only after repeating I
will be able to know for sure if I am right
VC RAKU CLAYBODY C2
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
kaolin 1200.
ball clay 600.0
Talc 540.0
alumina oxide 360.0
Molochite Grog 300.0
Bentonite 60.00
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
=20
Seger Weight%
KNO 0.026 0.41%
CaO 0.019 0.20%
MgO 0.955 6.95%
Al2O3 2.369 43.60%
SiO2 4.480 48.63%
TiO2 0.015 0.22%
K2O 0.020 0.34%
Na2O 0.006 0.07%
Al:Si 1.89 =20
Expan. 4.82 =20
ST 470.92 =20
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
It was planed for raku and works good at ^6
For more details go to my site
=85and I will join my family to the daily soap opera
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
My crystal glazes:
http://members4.clubphoto.com/ababi306910/894659/
http://members4.clubphoto.com/ababi306910/1310421/
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910
http://www.matrix2000.co.nz/Matrix%20Demo/Ababi.htm
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Ellie Blair
Sent: Wednesday, August 06, 2003 5:28 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Glaze problem for the gurus
Hi Ron
Here is my base glaze recipe.
Ferro Frit 3110 54.0
Zinc Oxide 24.6
Flint 14.9
titanium 4.0
epk kaolin .5
Manganese dioxide 4%
Black nickel 1%
also
Base + 4% red iron oxide
These are the two that I have the most crazing on. It is not so severe
that it cracks the glaze all the way through but it is noticeable and I
would like to correct it. What I have been doing hasn't been working. =20
Thanks
Ellie Blair
blairea53@msn.com
----- Original Message -----
From: Ron Roy
Sent: Wednesday, August 06, 2003 2:05 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Glaze problem for the gurus
All the oxides we use have different rates of expansion and contraction
-
but unless you are using significant amounts I would not expect them to
cause crazing.
I am looking at the list of oxides and their relative expansion rates in
the back of the Hamer book - page 379 in the 4th edition - and I see no
correlation with your results.
I suspect this may have to do with the type of crystals and how they
affect
the glaze surrounding the crystals.
When crystals from they take silica from the surrounding glaze - silica
starved glazes will be more susceptible to crazing.
If you want to send me your base glaze I may be able to adjust it - or
perhaps you can add some silica to it till it stops crazing.
This is mostly guess work on my part - I have no experience with crystal
glazes.
RR
>I am having a problem with crazing in my crystalline glazes. I use the
>same base glaze just different oxides for color. The crazing is the
worst
>on glazes containing manganese/black nickel or cobalt carbonate. The
pots
>are all made from the same clay and bisque fired to 08. The treatment
>during firing is the same for all of the glazes so why are some and not
>all crazing?
>Thanks
>Ellie Blair
>blairea53@msn.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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________________________________________________________________________
______
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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