John Post on wed 7 sep 05
This is a glaze I developed using Ian Currie's grid method.
It's a nice soft buttery magnesium matte glaze.
I call it Post's 244
The unity formula has .4 magnesium and .4 calcium with another .2 of
other fluxes. Thus the title 244
It is a cone 6 glaze fired with a slow cool.
It feels great on both the dark body and the light body I have tried it
on, though the dark is richer visually.
28.7 EPK
21.5 Frit 3110
16.9 Dolomite
2.9 Talc
30 Flint
0.18 Na2O
.02 K2O
.4 MgO
.4 CaO
.41 Al2O3
.03 B2O3
3.47 SiO2
expansion is low at 61.7 x 10e-7 per degree C
Now I know that this glaze does not fall into the standard limit formula
range for a stable cone 6 glazes to use with colorants. But it is a
smooth as a baby's butt and feels great to the touch. Since I explored
a couple of Currie grids with magnesium at cone 6, I was trying to
develop a glaze that felt the softest to the touch and this one was it.
If you try this glaze with colorants, send it in to a lab to have it
tested. Do the homework if you choose to make it yours.
Cheers,
John Post
Sterling Heights, Michigan
Ron Roy on fri 9 sep 05
Hi John,
Good of you to post this - interesting.
As I was looking at the recipe and the molecular formula it occured to me
that there might be a problem or two - that much 3110 is probably goi g to
deflocc the glaze depending on the local water - and the expansion is a
bit low so I though I would reformulate it - mostly just to see if it could
be done with another frit. There is also a lot of clay in you orgional -
potential for crawling perhaps?
While doing that it also occured to me that it might be somewhat underfired
- does it smooth out well?
This is what I came up with.
EPK ---------13.5
Frit - 3124 - 5.0
Custer ------ 35.0 (can do with g200 - easy to do)
Dolomite - 19.5
Talc --------- 1.0
Silica ------ 26.0
Total ----- 100.0
If you try it let me know if it look s and feels the same please.
Best regards - RR
>This is a glaze I developed using Ian Currie's grid method.
>It's a nice soft buttery magnesium matte glaze.
>
>I call it Post's 244
>The unity formula has .4 magnesium and .4 calcium with another .2 of
>other fluxes. Thus the title 244
>It is a cone 6 glaze fired with a slow cool.
>It feels great on both the dark body and the light body I have tried it
>on, though the dark is richer visually.
>
>28.7 EPK
>21.5 Frit 3110
>16.9 Dolomite
>2.9 Talc
>30 Flint
>
>0.18 Na2O
>.02 K2O
>.4 MgO
>.4 CaO
>
>.41 Al2O3
>.03 B2O3
>
>3.47 SiO2
>
>expansion is low at 61.7 x 10e-7 per degree C
>
>Now I know that this glaze does not fall into the standard limit formula
>range for a stable cone 6 glazes to use with colorants. But it is a
>smooth as a baby's butt and feels great to the touch. Since I explored
>a couple of Currie grids with magnesium at cone 6, I was trying to
>develop a glaze that felt the softest to the touch and this one was it.
>If you try this glaze with colorants, send it in to a lab to have it
>tested. Do the homework if you choose to make it yours.
>
>Cheers,
>John Post
>Sterling Heights, Michigan
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Lou Roess on sat 10 sep 05
Ron, does this glaze come out white without the addition of any
opacifiers? If so is it the dolomite and talc that make it white?
Lou in Colorado
On Sep 9, 2005, at 11:12 AM, Ron Roy wrote:
>
> This is what I came up with.
>
> EPK ---------13.5
> Frit - 3124 - 5.0
> Custer ------ 35.0 (can do with g200 - easy to do)
> Dolomite - 19.5
> Talc --------- 1.0
> Silica ------ 26.0
> Total ----- 100.0
>
> If you try it let me know if it look s and feels the same please.
>
> Best regards - RR
>
>
John Post on tue 13 sep 05
I posted some pictures of the fat cone 6 white on a website.
I made up the two variations suggested on clayart. One by RR and one by
Bill Edwards.
When I have more time, I will discuss how I thought the tests turned
out, but for now you can see the results here...
http://www.wideopenwest.com/~jpost4400/
I will also answer a couple of the private emails I got with questions
later today.
Gotta go... early morning staff meeting....sheesh those are the hardest
to get to...start at 7:30am.
Cheers,
John Post
John Post on wed 14 sep 05
The whole experiment with Post's 244 was to develop a buttery magnesium
matte glaze at cone 6.
Stability and staying within the limits was not the goal.
Rhodes 32 is short of silica, yet mel has been using it for years.
I have run 2 Currie grids so far using magnesium as the main flux.
It appears to me as though the buttery smooth feel is dependent on not
only the magnesium, but on the relationship between it and silica and
alumina. I will add some copper to the Post's 244 and send it in for
lab testing...just because I am curious about it. I like it just the
way it is with its smooth fat white feel. I am not worried about it
leaching anything into food, because there are not any metals in it that
I am concerned about.
The 3 different variations I tried all worked ok. My favorite studio
and classroom glaze has 24% clay in it. The high clay content of the
Post's 244 is not a problem for me. I prefer glazes high in clay.
Ron's and Bill's variations worked fine. I think the application on
Bill's variation was a little thin and that may account for the clay
body showing more through his glaze. I think his idea of adding tin to
his variation will probably remedy that. Ron's variation was opaque. I
still think the original has a slightly more buttery surface than either
variation...but only marginally.
If you want to see the currie grid starting points I have now added
these to the bottom of my web page.
http://www.wideopenwest.com/~jpost4400/
Info about the grids.
The 244 grid fluxes are..
.18 Na2O
.20 K2O
.4 CaO
.4 MgO
The second grid I call Col1-3 and its fluxes are...
.14 Na2O
.05 K2O
.22 CaO
.6 MgO
.2 B2O3
Cheers,
John Post
Ron Roy on wed 14 sep 05
Hi Lou,
I have never seen the glaze by the way - and this revision has a lot less
frit than the original which had f 3110 in it.
It's a little over supplied with MgO but not that much - I have the feeling
that if it is opake it's because it's underfired - there is not much B203
and there is plenty of alumina and silica.
If it is melting properly - it would probably be a clear glaze - unless it
was cooled slow enough to allow the recrystalization of the excess MgO.
One of the "rules" for stability is - have the glaze properly melted.
RR
>Ron, does this glaze come out white without the addition of any
>opacifiers? If so is it the dolomite and talc that make it white?
>Lou in Colorado
>
>On Sep 9, 2005, at 11:12 AM, Ron Roy wrote:
>
>
>>
>> This is what I came up with.
>>
>> EPK ---------13.5
>> Frit - 3124 - 5.0
>> Custer ------ 35.0 (can do with g200 - easy to do)
>> Dolomite - 19.5
>> Talc --------- 1.0
>> Silica ------ 26.0
>> Total ----- 100.0
>>
>> If you try it let me know if it look s and feels the same please.
>>
>> Best regards - RR
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
John Post on thu 15 sep 05
Hi Lou,
The tests were in oxidation.
Cheers,
John
Lou Roess wrote:
> Ron, does this glaze come out white without the addition of any
> opacifiers? If so is it the dolomite and talc that make it white?
> Lou in Colorado
>
> On Sep 9, 2005, at 11:12 AM, Ron Roy wrote:
>
>
>>
>> This is what I came up with.
>>
>> EPK ---------13.5
>> Frit - 3124 - 5.0
>> Custer ------ 35.0 (can do with g200 - easy to do)
>> Dolomite - 19.5
>> Talc --------- 1.0
>> Silica ------ 26.0
>> Total ----- 100.0
>>
>> If you try it let me know if it look s and feels the same please.
>>
>> Best regards - RR
>>
>>
>
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>
>
Pam Cresswell on thu 15 sep 05
Hi guys, this is a glaze I came up with, fiddling around with recipe for a
waxy white. The original was nice, but not within food safe ranges, so I
fiddled with the ingredients and numbers till there was not much left of the
original, thus the new name. Anyway, it is a semi-fat glaze, translucent,
and I think very pretty. You could make it more opaque with additions of
white colorants of you choice. I have tested it on Flint Hills ^6 buff
stoneware with good result. If any of you want to give it a try, I would
love to hear how it does for you.
Pam
Pam's Frost
Matte white ^6 Oxidation
Whiting 21.4
Zinc Oxide 2.5
Nepheline Syenite 15.4
Kaolin--EPK 19.5
Flint 34.2
Spodumene 7.0
100
add
Tin Oxide 2.6
Ron Roy on mon 19 sep 05
It is not always so - that calcined (glomax) has a lower expansion than EPK
- the typical analysis I use for each one gives the EPK a lower expansion.
In fact - in the end - when you calculate any glaze - you are already
looking at the kaolin as calcined - that is one of the great advantage of
calculation. You see the glaze as a fired material without the complication
of those parts of materials that are lost on ignition.
You should think of Calcined clay as "stronger" than raw clay - so you
would need less of it when replacing it - to get the same glaze.
In fact - if you calcined the same clay you have in the original formula -
and used it in the same glaze (properly reduce in amount) - the calculated
expansion would be the same.
This is because the original glaze with the uncalcined clay would be
calculated as if the clay was calcined - because calculation treats all
materials as fired.
Every kaolin has a different expansion rate - some are lower and some are
higher. Trying to change the expansion of a glaze by changing a kaolin is
not going to work enough to make much difference by the way - much better
to concentrate on changing the fluxes in an intelligent way.
RR
>Calcined kaolin has a lower expansion than kaolin :
>
>A-Glomax :
>
> Na2O 0.44 Al2O3 63.43 SiO2 75.83
> K2O 0.56 TiO2 1.36
> Fe2O3 0.57
>
>Alumina:Silica ratio is 1.00:1.20
>Neutral:Acid ratio is 1.00:1.23
>Alk:Neut:Acid ratio is 1.00:63.43:77.76
>
>Expansion: 55.1 x 10e-7 per degree C
>
>
>B-EPK :
>
> Na2O 0.09 Al2O3 36.29 SiO2 75.38
> K2O 0.35 P2O5 0.16
> MgO 0.24 TiO2 0.46
> CaO 0.32 Fe2O3 0.49
>
>Alumina:Silica ratio is 1.00:2.08
>Neutral:Acid ratio is 1.00:2.11
>Alk:Neut:Acid ratio is 1.00:36.29:76.50
>
>Expansion: 50.4 x 10e-7 per degree C
>
>Maybe replacing all or part of the kaolin by calcined kaolin
>could help in lowering the expansion of a glaze containing
>this material.
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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