May Luk on thu 27 may 04
Hi Ron and Alisa and friends:
Further to the Glaze-cobalt with pink specks-oxidation post:-
Ball clay has more Silica then Kaolin/China Clay.
I did some currie grids a year ago with this cream yellow recipe and it's a
bit like Alisa's dolomite recipe way below;
Cream Yellow Stone ware; [I changed some material, the original is from the
archive]
Nepheline Sye___50
Dolomite________20
China Clay______20
Whiting_________10
Rutile__________7.5
Tin_____________5
1-The cream yellow turn a bit pink in the corner D where there's more
silica. [It could be just chrome flashing from neighbouring tile, not sure]
2-I added Chrome to the batch and there are purple / purple specks at the
area around corner D [Higher Silica]
Granted, I didn't put in cobalt and the two are not exact copies. My version
with the chrome is tin-chrome pink in high calcium base, innit? It appears
there's more calcium then magnesium in Alisa's recipe also. Is there a
relationship between the Mg and Ca? They both give matte glaze in high
amount. Is it for the colour response again?
From the currie grid, it seems the silica promotes specking. [not a fact
yet!!]
Thank you again to everyone who gave me the pointers for the cobalt speck
glaze. I feel like Popeye about to get my spinach!!
May
London, UK
=============================================================
When I look at this glaze as a Seger formula I see all the fluxes within
suggested limits - in other words - the MgO is high but not way high.
The other significant detail is - the silica is way low - as it usually is
in a clay matte glaze.
RR
The question becomes - is it necessary to have low silica to get the
specking?
=============================================================
When I was trying to get a cobalt green, I found that a base with Dolomite
(magnesium) will produce a blue or grey blue, with lavendar or pink
speckling. I use my cone 6 Wodo White, which is
------------------
50 Neph. Sye
25 Dolomite
5.8 Wolalstonite
20 Ball Clay
ADD
1 Colbalt oxide
1 Tin Oxide
------------------
I have tried the same colorants in dolomite bases, with more or less
lavender blues as a result. Using Ball Clay instead of Kaolin, if that is
a posibility.....
Alisa
Alisa Liskin Clausen on fri 28 may 04
>2-I added Chrome to the batch and there are purple / purple specks at the
>area around corner D [Higher Silica]
>
>
>From the currie grid, it seems the silica promotes specking. [not a fact
>yet!!]
>
>
Dear May,
I will personally be interested to hear your findings. It is interesting
to hear from your grid testing which may confirm some of my intuition
testing. I have just started a series of tests where I am switching Kaolin
for Ball Clay and the reverse, to see the effects. I have a working cross
grid where I list the color, surface texture, and degree of mattness
against the Ball Clay and Kaolin's attributes such as Alumina, silica, Iron
Oxide, Titanium and if the glaze crazes or shivers. Homemade, very, but
when I get some visual results, I can put them on GlazeMaster and see if I
can figure out the whole picture.
regards from Alisa
May Luk on sat 29 may 04
Hi Alisa;
May I ask if you are using local ball clay and kaolin? Do you have the
analysis? Or if you have the web site, I can find it myself. I'm having a
separate conversation with a clay supplier regarding clay from different
continents.
I'm thrilled that we are doing tests that compliment each other's curiosity
and learning. I'll definitely share my findings.
The glaze calculation is really helping me understand. But without the
firing, numbers don't mean a whole lot. Truely, I prefer numbers starting
with a =A3/$/Euro sign. :-)
Best regards
May
London, UK
Alisa Liskin Clausen on mon 31 may 04
On Sat, 29 May 2004 12:39:18 +0100, May Luk
wrote:
>Hi Alisa;
>
>May I ask if you are using local ball clay and kaolin? Do you have the
>analysis? Or if you have the web site, I can find it myself. I'm having a
>separate conversation with a clay supplier regarding clay from different
>continents.
Dear May,
The Ball Clay is called W.B.B. - TWVD and I think imported from England.
MW 258. I do not have more.
The Kaolin is called E, and I also think it from your side.
It is in the catalog like this.
48,5 Si02
36,5 Al203
1,1 Fe203
2,7 K2O/Na20
A lot of our materials are from England's Matthey Johnson, so we can easily
compare notes.
regards from Alisa
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