Randy McCall on sun 14 dec 03
What happens when you incrementally add Magnesium Carbonate to a glaze? =
At what point do you get crawling usually? Does anyone have any tests =
with pictures?
Ababi on sun 14 dec 03
? Does anyone have any tests with pictures
==========
Yes
It is very easy or very complicated.
The easy way: to your glaze add 10 20 30 40 and 50 magnesium carbonate
In my tests pages you will see what I have done.
(How do you say tests?)
Ababi
http://ababi.active.co.il
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Randy
McCall
Sent: Sunday, December 14, 2003 5:23 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Adding Magnesium Carbonate to Glazes?
What happens when you incrementally add Magnesium Carbonate to a glaze?
At what point do you get crawling usually? Does anyone have any tests
with pictures?
.
iandol on mon 15 dec 03
Dear Randy McCall,=20
You ask <a glaze? At what point do you get crawling usually? Does anyone have any =
tests with pictures? >>
I would have thought that one of the glaze calculation programs would =
provide this information if you were wishing to modify an existing glaze =
to induce Crawling of Balling.
Perhaps if you were to send your own example to Ababi he would do the =
calcs for you and give predictions.
However, if you have in mind a research project based on your own kiln =
situation and materials availability the best thing to do is to make =
line blends or cross blends or employ Ian Curries's methodology and =
"test, test, test..."
Best regards,=20
Alisa Clausen on mon 15 dec 03
A simple line blend with increments of 10% showed crawling after 30% was
added to a premixed white glaze, in the tests I made.
regards from Alisa in Denmark
Lois Ruben Aronow on mon 15 dec 03
I didn't see the original post for this one --
I agree with Alisa - add in increments of 10% up to 30%, then add in
smaller increments. you can go up to and over 50% before it starts
looking really nasty. =20
The glaze you get depends not only on how much mag carb you are using,
but what base, and what types of effects you're loking for. =20
Use a good kiln wash - crawling glazes spit like crazy.
And Ababi had great photos of different textured glazes on his web
site.
************
Lois Ruben Aronow
www.loisaronow.com
Modern Porcelain and Tableware
The Tattoo is back!
Randy McCall on mon 15 dec 03
Alisa thanks that is what I was looking for. Will try with some of the
glazes I have on hand.
----- Original Message -----
From: "Alisa Clausen"
To:
Sent: Monday, December 15, 2003 3:30 AM
Subject: Re: Adding Magnesium Carbonate to Glazes?
> A simple line blend with increments of 10% showed crawling after 30% was
> added to a premixed white glaze, in the tests I made.
>
> regards from Alisa in Denmark
>
>
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>
Paul Lewing on tue 16 dec 03
on 12/14/03 10:31 PM, iandol at iandol@TELL.NET.AU wrote:
> I would have thought that one of the glaze calculation programs would =
> provide this information if you were wishing to modify an existing glaze =
> to induce Crawling of Balling.
Ivor, this is not the kind of information that you can get from a
calculation program. I think the crawling effect from mag carb is a result
of its physically shrinking in drying. Calculation programs analyze the
fired glaze. They don't tell you much about this kind of physical problem.
But I'm sure that after you made a few crawling glazes with the stuff, you'd
know how many molecular equivalents of MgO you'd need to make it crawl if
you got them all from mag carb. But as far as telling you outright in so
many words, or even telling you in reference to some kind of limit formulas,
no, they won't do that.
Paul Lewing, Seattle
iandol on tue 16 dec 03
I have a sample tile of a high Magnesia glaze where the slop has been =
applied in three thicknesses. There are three differing frequencies of =
balling.
Where the glaze was applied as a thin layer the cell size is small with =
a flat surface. Where the glaze was thickest the cell size is large, =
between 5 and 10 mm and there is an almost spherical meniscus. In =
between some of the cells have fused to make amoebic shapes.
Definitely interesting and decorative.
Best regards,=20
Ivor Lewis. Redhill, South Australia
Ababi on wed 17 dec 03
This is my third attempt to answer this letter.
I do not use the surface tension when I create or develop a crawling
glaze.
I use it mainly when I make a waxy glaze. In this case trying to add to
typical waxy glaze colorants - except cobalt ox. Or - carb. - will yield
an ugly result.
When I was afraid I would not be able to buy cryolite, I tried to
duplicate my Supercrawl glaze. (It is mine but the father was Behrens's
Stony Fissured and the mother was Lana Wilson's Textural Crawl)
http://members4.clubphoto.com/ababi306910/185990/
The results:
http://members4.clubphoto.com/ababi306910/981929/
Look at glaze 2 and three I think I started from #3 it is an ugly waxy
glaze.
Now I remember I made the three corners leaning on my experience with
earlier tests/glazes.
The first recipe #3 already includes a lot of spodumen that replaces the
magnesium carbonate as a low ST (Surface tension) material;
ABABISCRAWL__#3
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Cone 6 1222 deg.C. -
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
SPODUMENE 21.75
RED CLAY (GRT) 21.75
FRIT A 2120 p 30.25
Magnesium Carb Light 16.75
ULTROX 9.50
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Seger Weight%
KNO 0.307 6.73%
CaO 0.276 5.47%
MgO 0.171 2.43%
Li2O 0.246 2.60%
Al2O3 0.373 13.44%
SiO2 2.951 62.64%
ZrO2 0.151 6.56%
TiO2 0.004 0.12%
K2O 0.001 0.04%
Na2O 0.306 6.69%
Al:Si 7.90
Expan. 7.15
ST 364.48
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
To make a similar glaze that will yield red or mauve I must remove as
much MgO as possible the result:
ABABI WAXY RED NO 5
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Cone 6 1222 deg.C. -
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
spodumen 10.50
kaolin CC31 26.50
frit A 2120 23.00
Wollastonite 27.80
Quartz 12.20
Tin Oxide 6.20
Chrome Oxide 0.35
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Seger Weight%
KNO 0.291 7.49%
CaO 0.611 13.70%
MgO 0.027 0.43%
Li2O 0.071 0.85%
Al2O3 0.343 13.96%
SiO2 2.645 63.55%
TiO2 0.001 0.03%
K2O 0.021 0.79%
Na2O 0.270 6.70%
Al:Si 7.72
Expan. 8.33
ST 362.68
I use the surface tension as an aid to create similar results to a
different glaze together with the Si: Al and sometimes with the
expansion - to duplicate results not to convert the recipe.
Because I am such a nice fellow ( ...said the mirror) I shall try to
duplicate it to "yours"- Frit 2120 is similar to 3110 I can convert
recipes with 3110 but cannot convert recipes from 2120 to 3110. In this
case I shall play around with the ST:
ABABI WAXY RED NO 5 US&CA
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Cone 6 1222 deg.C. -
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
EPK Kaolin 18.70
frit 3110 27.50
Wollastonite 24.20
frit 3195 12.00
spodumen 17.60
Tin Oxide 6.20
Chrome Oxide 0.35
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Seger Weight%
KNO 0.233 5.92%
CaO 0.623 13.75%
MgO 0.025 0.39%
Li2O 0.120 1.41%
Al2O3 0.378 15.15%
B2O3 0.131 3.59%
SiO2 2.527 59.78%
K2O 0.019 0.69%
Na2O 0.214 5.23%
Al:Si 6.69
Expan. 7.77
ST 362.62
Will it work? I do not know: You can try and tell me- APPLY very thick
allow dripping down like candle's melted paraffin.
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://ababi.active.co.il
http://www.matrix2000.co.nz/Matrix%20Demo/Ababi.htm
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of iandol
Sent: Monday, December 15, 2003 8:31 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Adding Magnesium Carbonate to Glazes?
Dear Randy McCall,
You ask <a glaze? At what point do you get crawling usually? Does anyone have any
tests with pictures? >>
I would have thought that one of the glaze calculation programs would
provide this information if you were wishing to modify an existing glaze
to induce Crawling of Balling.
Perhaps if you were to send your own example to Ababi he would do the
calcs for you and give predictions.
However, if you have in mind a research project based on your own kiln
situation and materials availability the best thing to do is to make
line blends or cross blends or employ Ian Curries's methodology and
"test, test, test..."
Best regards,
.
iandol on thu 18 dec 03
Dear Paul Lewing,
Thanks for that input about Mag Carb.
But I think there are two problems we cope with here. Yes, glazes high =
in Mag Carb do shrink as they dry and break into lozenge patterns. So =
there is no doubt that this will provide weaknesses in the coating where =
shrinkage during melting will cause breaks in the surface.
But then you have to ask why the glaze does not efficiently wet the =
maturing clay and flow out so that the breaks coalesce to give a =
continuous surface. The answer here seems to be strength of the surface =
tension in the molten glaze. My inference would be that excess Mag Carb =
increases the surface tension. I thought this factor was known for all =
of the Fluxing and Melting agents used in our glazes. Hamer certainly =
gives surface tension a mention and that other influential factor, =
viscosity. So it seems reasonable to consider that these might be =
incorporated in the newer Glaze Calc Programs.=20
Best regards,
Ivor Lewis. Redhill, South Australia
Ron Roy on thu 18 dec 03
Hi Randy,
Eventually it will start to crawl because of it's initial high shrinkage -
the more you add the larger the spaces left after the glaze is fired.
Most glazes crack up to some extent as they dry and/or at the lower end of
the glaze firing. Most times those cracks get sealed over because - as
glazes melt they usually want to flow together - especially on vertical
surfaces so you don't notice that the glazes cracked up when sintering.
The exception is when the glazes have a high viscosity. The two materials
that have the highest viscosity are MgO and Al2O3 - so high alumina glazes
are called "stiff glazes" they don't want to flow. Same for high Magnesia
glazes.
Hamer has a good explanation of viscosity and crawling.
RR
>What happens when you incrementally add Magnesium Carbonate to a glaze?
>At what point do you get crawling usually? Does anyone have any tests
>with pictures?
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ababi on thu 18 dec 03
It is not enough to have high magnesium carbonate. The glaze must be
applied several layers- until it cracks.
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://ababi.active.co.il
http://www.matrix2000.co.nz/Matrix%20Demo/Ababi.htm
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Ron Roy
Sent: Thursday, December 18, 2003 7:04 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Adding Magnesium Carbonate to Glazes?
Hi Randy,
Eventually it will start to crawl because of it's initial high shrinkage
-
the more you add the larger the spaces left after the glaze is fired.
Most glazes crack up to some extent as they dry and/or at the lower end
of
the glaze firing. Most times those cracks get sealed over because - as
glazes melt they usually want to flow together - especially on vertical
surfaces so you don't notice that the glazes cracked up when sintering.
The exception is when the glazes have a high viscosity. The two
materials
that have the highest viscosity are MgO and Al2O3 - so high alumina
glazes
are called "stiff glazes" they don't want to flow. Same for high
Magnesia
glazes.
Hamer has a good explanation of viscosity and crawling.
RR
>What happens when you incrementally add Magnesium Carbonate to a glaze?
>At what point do you get crawling usually? Does anyone have any tests
>with pictures?
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
________________________________________________________________________
______
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.
Paul Lewing on thu 18 dec 03
on 12/17/03 6:46 PM, iandol at iandol@TELL.NET.AU wrote:
> My inference would be that excess Mag Carb =
> increases the surface tension. I thought this factor was known for all =
> of the Fluxing and Melting agents used in our glazes. Hamer certainly =
> gives surface tension a mention and that other influential factor, =
> viscosity. So it seems reasonable to consider that these might be =
> incorporated in the newer Glaze Calc Programs.
Right as usual, Ivor, as far as it goes. Hamer does indeed have a ranking
of the various oxides by both surface tension and by viscosity. The two
scales are very similar, by the way.
And some calculation programs do use these to try to predict glaze behavior.
Matrix gives you a number for a surface tension index, and I believe
GlazeChem produces a viscosity index number. I do not have GlazeChem, and
my version of Matrix is an old Mac version that doesn't work very well. So
while I've seen that number for every glaze I ever put into Matrix, I can't
use it enough to get familiar with it. So I don't know how useful a
predictor it would be. Perhaps someone more familiar with it could comment.
lawrence Ewing, are you listening?
I do know that in the case of both of these indices, the number generated is
a ranking, not a measurement. Which means that the programmers have not
used an empirical measurement of viscosity or surface tension for each
oxide, then generated their index number by determining the proportion of
each oxide. What they've done is assign a number to each oxide in order of
high or low viscosity or surface tension, then used the percent by weight
analysis to generate a number that ranks the glaze in comparison to other
glazes. I hope that made sense to you. Anyway, they might be useful
numbers in telling you whether your recipe is relatively high or low, but
they don''t actually measure anything.
Paul Lewing, Seattle
iandol on sat 20 dec 03
Dear Paul Lewing,
Thank you for elaborating on the issue of the behaviour of Magnesium
Carbonate and our the ability to predict the effects of incremental
addition to any selected glaze composition using a glaze calc program.
From what you say, it would appear that all we have to go on is some
informed and intelligent guess work.
I would confirm from experience the opinion of Ababi, that thicker
coatings of high magnesia glazes exhibit a lesser degree of
reticulation with larger glaze elements and extended exposure of the
background clay. High domed beads of translucent to white opaque glaze
can be a striking decorative motif used with a little design wisdom.
Best regards,
Ivor Lewis. Redhill, South Australia
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