Joan & Tom Woodward on mon 5 aug 02
I have a happy report and two questions borne of ignorance. =20
The happy news flash: I've created two glazes that I like a lot using R =
& J's High Calcium Semimatte Base 1. The first gives a nice cobalt blue =
- too ordinary for some of you, but I find it rich and useful. It's 5% =
rutile, 2% cobalt carbonate, and 1% copper carbonate. The second is a =
lovely variegated green made with 6% rutile, 4% copper carbonate, and =
0.5% cobalt carbonate. The green layers over the blue nicely, too.
My first question is whether I can substitute Frit 3124 for 3134 in R & =
J's Glassy Base Glaze 1? I think I may have done it accidentally when I =
mixed my test batch which worked beautifully over various underglazes. =
When I was getting around to ordering supplies, I noticed that I didn't =
have any bag or container with 3134, but I did have 3124.
Similarly, I've run out of cobalt carbonate but have some old cobalt =
oxide. Do I use 2/3 the amount of cobalt carbonate in glazes like =
Variegated Slate Blue and my new blue noted above to get essentially the =
same results?
Unfortunately, I have not yet taken Ian Currie's course or any other of =
that ilk, nor do I have a glaze calc. program - yet. So any assistance =
will be appreciated.
Thanks much.
Joan in Colorado where blessed rain last night and today helped our =
parched land.
Ababi on tue 6 aug 02
I shall bring the book from my studio and send you off list the converted recipe.
Once when I had thought disabled kids from Rahat , our neighbor town I said: "This
claybody called K-123". Their teacher corrected my words: "this glaze number is
K-123. She was wrong and I did not want to fight with her , she would not understand.
K-123, and A 48 are names given in numbers to different characterizes claybodies.
The same about frits Frit 3134 and frit 3124 are different. I give them now different
names, please tell me if you will change them one for one:
3134: None alumina higher silica calcium borate frit and expansion (In my computer)
9.7
To 3124: High alumina lower silica calcium borate frit
11.3
You are not changing number for number ( Except in Australia) there you change
3110 to it' Oz name: 4110
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910/
http://www.milkywayceramics.com/cgallery/asharon.htm
---------- Original Message ----------
>I have a happy report and two questions borne of ignorance.
>The happy news flash: I've created two glazes that I like a lot using R & J's High
Calcium
>Semimatte Base 1. The first gives a nice cobalt blue - too ordinary for some of you,
but I
>find it rich and useful. It's 5% rutile, 2% cobalt carbonate, and 1% copper carbonate.
The
>second is a lovely variegated green made with 6% rutile, 4% copper carbonate, and
0.5%
>cobalt carbonate. The green layers over the blue nicely, too.
>My first question is whether I can substitute Frit 3124 for 3134 in R & J's Glassy
Base Glaze
>1? I think I may have done it accidentally when I mixed my test batch which worked
>beautifully over various underglazes. When I was getting around to ordering
supplies, I
>noticed that I didn't have any bag or container with 3134, but I did have 3124.
>Similarly, I've run out of cobalt carbonate but have some old cobalt oxide. Do I use
2/3 the
>amount of cobalt carbonate in glazes like Variegated Slate Blue and my new blue
noted
>above to get essentially the same results?
>Unfortunately, I have not yet taken Ian Currie's course or any other of that ilk, nor do I
have a
>glaze calc. program - yet. So any assistance will be appreciated.
>Thanks much.
>Joan in Colorado where blessed rain last night and today helped our parched land.
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
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John Hesselberth on tue 6 aug 02
Hi Joan,
I am delighted you are having some success with our glazes and beginning
to explore variants of them. With respect to your questions:
Substituting 3124 for 3134 in Glossy Base Glaze 1 will result in 1) more
alumina, 2) more silica and 3) less boron. The flux balance and Si/Al
ratio are slightly different, but not grossly so.
In terms of practical effects, this glaze will be harder to melt. It may
not be fully melted at cone 6 and, therefore, not as stable as the
original. It also has a noticeably lower calculated coefficient of
expansion than the original. It could be low enough to precipitate
dunting or shivering on some clay bodies. It is not a change I could
support without thorough testing for leaching and shivering/dunting.
On your cobalt question, the carbonate has a molecular weight of 118.95
and the oxide (CoO) is 74.94. The ratio is .63 so your 2/3 is a good
estimate of the theoretical difference. Unfortunately life is sometimes
not that simple. Both materials are less than pure. I am currently at
the beach and don't have all my reference materials with me, but I
recall that Tom Buck wrote a good summary of the situation a couple
years ago on Clayart. Maybe he will repost that or tell you how to find
it. Bottom line though--start at 2/3 and be prepared to adjust for your
particular batches of materials.
Regards,
John (thankful to our Canadian friends who just sent us some of their
cool summer air)
On Monday, August 5, 2002, at 11:20 PM, Joan & Tom Woodward wrote:
I have a happy report and two questions borne of ignorance.
The happy news flash: I've created two glazes that I like a lot using
R & J's High Calcium Semimatte Base 1. The first gives a nice cobalt
blue - too ordinary for some of you, but I find it rich and useful.
It's 5% rutile, 2% cobalt carbonate, and 1% copper carbonate. The
second is a lovely variegated green made with 6% rutile, 4% copper
carbonate, and 0.5% cobalt carbonate. The green layers over the blue
nicely, too.
My first question is whether I can substitute Frit 3124 for 3134 in R &
J's Glassy Base Glaze 1? I think I may have done it accidentally when I
mixed my test batch which worked beautifully over various underglazes.
When I was getting around to ordering supplies, I noticed that I didn't
have any bag or container with 3134, but I did have 3124.
Similarly, I've run out of cobalt carbonate but have some old cobalt
oxide. Do I use 2/3 the amount of cobalt carbonate in glazes like
Variegated Slate Blue and my new blue noted above to get essentially the
same results?
Unfortunately, I have not yet taken Ian Currie's course or any other of
that ilk, nor do I have a glaze calc. program - yet. So any assistance
will be appreciated.
Thanks much.
Joan in Colorado where blessed rain last night and today helped our
parched land.
>
Ron Roy on wed 7 aug 02
Hi Joan,
I'm answering this on ClayArt because there have been other questions about
these two frits.
If you sub 3124 for 3134 in glossy base #1 you get quite a different glaze
- the fluxes are not too different but the boron is down quite a bit and
the alumina and silica are up more than a little. This makes the glaze more
refractory, raises the ratio of a silica to alumina and lowers expansion.
This does not mean the glaze looks different but the physical attributes
are different.
The lower expansion of this glaze (with 3124) makes it unlikely to craze on
most of the bodies we use - but if the body has a higher than normal
expansion there may be problems in certain situations and with certain
forms - so test it well - just glaze the inside of a thinly thrown (or
trimmed) cylinder - say 4" wide and 6" tall - glaze the inside only - apply
glaze thicker than normal - after firing freeze it for 24 hours - then pour
boiling water in while it's still frozen - do it in the sink in case it
cracks. An even better test would be a flat bottomed casserole - the bigger
the ware the more stresses are developed.
Round bottomed dishes are less likely to crack because stress is not
concentrated in the angle between bottom and sides.
The reason that tea pots sometimes crack in use is because the inside glaze
has too low an expansion/contraction rate - it simply does not contract on
cooling as much as the clay does - setting up stress that can crack the
ware during cooling or - later during use. One of the problems with liner
glazes - when opacifying with zirconium silicate you automatically lower
expansion of most of the glazes potters use - so if the expansion of the
glaze is low to start with the problem is made worse.
If you have used the 5 glazes provided to ascertain fit numbers for the
clays you use - the number for the glaze with f3124 is 372.13 and the
number for the glaze with f3134 is 404.82 using the scale I use.
Please let us know the results if you decide to do the fit testing.
RR
>I have a happy report and two questions borne of ignorance.
>
>The happy news flash: I've created two glazes that I like a lot using R &
>J's High Calcium Semimatte Base 1. The first gives a nice cobalt blue -
>too ordinary for some of you, but I find it rich and useful. It's 5%
>rutile, 2% cobalt carbonate, and 1% copper carbonate. The second is a
>lovely variegated green made with 6% rutile, 4% copper carbonate, and
>0.5% cobalt carbonate. The green layers over the blue nicely, too.
>
>My first question is whether I can substitute Frit 3124 for 3134 in R &
>J's Glassy Base Glaze 1? I think I may have done it accidentally when I
>mixed my test batch which worked beautifully over various underglazes.
>When I was getting around to ordering supplies, I noticed that I didn't
>have any bag or container with 3134, but I did have 3124.
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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