Don & June MacDonald on sun 28 oct 01
Hi Jeanne: I tried for a year to get something, anything to fit Alpine
White Clay from Seattle. The answer I came up with is, nothing fits! I
used this clay in a glaze class I was teaching in order to extend my own
research, (also had the students use another clay body for test tiles so
they could compare) and we had plenty of success with glazes fitting on
the other body, but no success with Alpine White. The tests were done in
both Cone 6 oxidation and Cone 6 reduction.
I asked Seattle Potters Supply about the problem and was told to bisque
hotter, Cone 04 or above, but then you have the problem of dipping
glazes not going on quite as well. Too bad, its a great clay to throw.
June from B.C.
Jeanne Stolberg wrote:
>
> Help! Am trying to get a clear glaze to work on a white stoneware, fired to
> range ^4-6 ox. (It's called Alpine White, from Seattle Pottery Supply). Have
> tested several clear glaze recipes, to no avail, they all craze. What
> ingredients can I play around with - add more, or less of, to try to get a
> glaze that fits? These are mugs with underglaze decoration.
> Some glazes I've tried, some from Clayart:
>
> 5x20 Clear:
> 20 EPK; 20 FRit 3134; 20 Silica; 20 Custer; 20 Wollastonite
>
> Clear:
> 12.5 Whiting; 12.5 EPK; 20 Neph. Sye; 25 Frit 3134; 30 Flint
>
> EZ Clear:
> 50 Frit 3134; 30 EPK; 20 Silica
>
> Clear:
> 30 Neph Sye; 8 Wollastonite; 21 Gerstley Borate; 31 Silica; 10 EPK
>
> Shiny Clear GTB-1
> 8 Whiting; 27 Gerstley Borate; 39 Neph Sye; 8 EPK; 18 Silica
>
> G1214W Clear
> 10 Wollastonite; 25 Frit 3134; 25 EPK; 25 Flint; 15 F4 Kona Feldspar
>
> The last one came the closest, but still a bit crazed, maybe I should dink
> around with that one.
> I seem to be a glaze klutz, I sure would appreciate any advice you can throw
> my way!
> Thank you!!
> Jeanne, in cold, wet, rainy Sitka by the Sea, Alaska.
>
> ______________________________________________________________________________
> 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.
Wade Blocker on sun 28 oct 01
Jeanne,
Do you fire your stoneware cone 4 to 6, or is that stoneware rated for
that range? If it is a stoneware body with a wide firing range eg cone 4 to
9 you will never find a glaze that fits without crazing. Make sure that
your clay really has a maturation range from cone 4 to 6. Mia in ABQ
Ron Roy on sun 28 oct 01
Hi Jeanne,
The calculated expansion for #1 is 436 on the scale I use
#2 is 465
#3 is 372 ( the boron in this glaze is just a bit over 12% so in reality
this number will be a bit higher.
#4 is 399
#5 is 522
#6 is 333
As you can see - the last one - you said came closest is the lowest - but
With the C6 bodies I have experience with I would only expect #2 and #5 to
craze - so I have to ask a few questions before I start adjusting #6 to
stop any crazing.
Question #1 - Are we sure it's crazing on #6 - sometimes it's what we call
shivering - when that happens the cracking glaze pattern is usually
different in that the lines tend to be parallel. Try mixing equal amounts
of #1 and number 6 - that glaze will have a calculated expansion of about
385 - just combine the materials for both and divide by 2
EPK - 22.5
3134 - 22.5
Silica - 22.5
Custer - 10.0
wollast - 15.0
F4 - 7.5
Total - 100.0
There are two other reasons a glaze can craze even though the basic
expansion is OK for the body,
Question #2 - How long is your firing, are you using large cones to monitor
the final temperature and how long do you soak at the end? Not giving the
glaze a chance to bond well with the clay can give very small fit
tolerances.
Question #3 How fast is your cooling from dull red heat to kiln opening? If
a glaze is cooled fast from say opening your kiln too soon you can get
crazing - simply because the glaze cooles before the clay and contracts to
quickly. We assume you have turned off any venting after shut off. If not
refire all and turn vent off at end of firing.
This may result in some of the glazes not being clear (fast cooling promots
clears) but if that is the case you have to turn off the vent just before
your glazes solidify - probably around 700C
So let me know as much as you can an we will go from there.
RR
>Help! Am trying to get a clear glaze to work on a white stoneware, fired to
>range ^4-6 ox. (It's called Alpine White, from Seattle Pottery Supply). Have
>tested several clear glaze recipes, to no avail, they all craze. What
>ingredients can I play around with - add more, or less of, to try to get a
>glaze that fits? These are mugs with underglaze decoration.
>Some glazes I've tried, some from Clayart:
>
>5x20 Clear:
>20 EPK; 20 FRit 3134; 20 Silica; 20 Custer; 20 Wollastonite
>
>Clear:
>12.5 Whiting; 12.5 EPK; 20 Neph. Sye; 25 Frit 3134; 30 Flint
>
>EZ Clear:
>50 Frit 3134; 30 EPK; 20 Silica
>
>Clear:
>30 Neph Sye; 8 Wollastonite; 21 Gerstley Borate; 31 Silica; 10 EPK
>
>Shiny Clear GTB-1
>8 Whiting; 27 Gerstley Borate; 39 Neph Sye; 8 EPK; 18 Silica
>
>G1214W Clear
>10 Wollastonite; 25 Frit 3134; 25 EPK; 25 Flint; 15 F4 Kona Feldspar
>
>The last one came the closest, but still a bit crazed, maybe I should dink
>around with that one.
>I seem to be a glaze klutz, I sure would appreciate any advice you can throw
>my way!
>Thank you!!
>Jeanne, in cold, wet, rainy Sitka by the Sea, Alaska.
>
>______________________________________________________________________________
>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.
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
Jeanne Stolberg on sun 28 oct 01
Help! Am trying to get a clear glaze to work on a white stoneware, fired to
range ^4-6 ox. (It's called Alpine White, from Seattle Pottery Supply). Have
tested several clear glaze recipes, to no avail, they all craze. What
ingredients can I play around with - add more, or less of, to try to get a
glaze that fits? These are mugs with underglaze decoration.
Some glazes I've tried, some from Clayart:
5x20 Clear:
20 EPK; 20 FRit 3134; 20 Silica; 20 Custer; 20 Wollastonite
Clear:
12.5 Whiting; 12.5 EPK; 20 Neph. Sye; 25 Frit 3134; 30 Flint
EZ Clear:
50 Frit 3134; 30 EPK; 20 Silica
Clear:
30 Neph Sye; 8 Wollastonite; 21 Gerstley Borate; 31 Silica; 10 EPK
Shiny Clear GTB-1
8 Whiting; 27 Gerstley Borate; 39 Neph Sye; 8 EPK; 18 Silica
G1214W Clear
10 Wollastonite; 25 Frit 3134; 25 EPK; 25 Flint; 15 F4 Kona Feldspar
The last one came the closest, but still a bit crazed, maybe I should dink
around with that one.
I seem to be a glaze klutz, I sure would appreciate any advice you can throw
my way!
Thank you!!
Jeanne, in cold, wet, rainy Sitka by the Sea, Alaska.
John Hesselberth on sun 28 oct 01
on 10/28/01 4:17 PM, Jeanne Stolberg at j.stolberg@ATT.NET wrote:
>
> G1214W Clear
> 10 Wollastonite; 25 Frit 3134; 25 EPK; 25 Flint; 15 F4 Kona Feldspar
>
> The last one came the closest, but still a bit crazed, maybe I should dink
> around with that one.
Hi Jeanne,
There are several ways to solve this one--I just picked a quick one for a
first try. I worked with your last recipe which you said was the closest.
Also I like it because it doesn't have any Gerstley Borate and has plenty of
clay for good glaze suspension in the bucket. I basically took out some of
the sodium and potassium (which are high expansion materials) and added some
magnesium--a low expansion material. I also ended up with a little less
silica and alumina but they are still plenty high for a good stable glaze.
Try this and let me know if it works. It has a calculated expansion of 63.5
x 10exp-7/degC vs. 67.6 for the original. That should be enough difference
to be noticeable and maybe enough to solve your problem. This clay body is
apparently quite low in expansion coefficient itself.
Regards, John
Glaze name: G1214W Clear--Mod I
Cone: 6
Color: Transparent Clear
Testing: Untested
Surface texture: Shiny or Glossy
Firing: Oxidation
Glaze type:
Recipe: Percent
frit 3134 25.00
F-4 Feldspar 5.00
Wollastonite 10.00
EPK 25.00
Flint 30.00
Talc 5.00
Totals: 100.00 %
Possible Health Hazards:
Flint: free silica-wear a NIOSH approved dust mask when handling dry
material
Talc: wear a NIOSH approved dust mask when handling dry material
Unity Formula for G1214W Clear--Mod I:
0.015 K2O 0.385 Al2O3 3.978 SiO2
0.178 Na2O 0.307 B2O3 0.004 TiO2
0.652 CaO 0.004 Fe2O3 10.3:1 Si:Al Ratio
0.156 MgO
Web site: http://www.frogpondpottery.com Email: john@frogpondpottery.com
"The life so short, the craft so long to learn." Chaucer's translation of
Hippocrates, 5th cent. B.C.
Jeanne Stolberg on mon 29 oct 01
Thanks for the word. Maybe I'll try B-mix 5 after I use this stuff up.
Jeanne S, Sitka
----- Original Message -----
From: Don & June MacDonald
To:
Sent: Sunday, October 28, 2001 6:28 PM
Subject: Re: crazing help
> Hi Jeanne: I tried for a year to get something, anything to fit Alpine
> White Clay from Seattle. The answer I came up with is, nothing fits!
Jeanne Stolberg on mon 29 oct 01
RR:
Some answers to your questions are inserted below. Sorry, I'm not very
scientific about it- I'm trying!
Today I'm testing another clear I had in the studio: 44.6% Colemanite (but I
used Gerstley B); 26.79 EPK, and 28.57 Flint, firing to ^4, applied thin.
Am up to 1100F at the moment IF I can trust my pyrometer. I will also try
the other suggestions below
Jeanne S.,Sitka
----- Original Message -----
From: Ron Roy
To:
Sent: Sunday, October 28, 2001 6:41 PM
Subject: Re: crazing help
> Question #1 - Are we sure it's crazing on #6 - sometimes it's what we call
> shivering - when that happens the cracking glaze pattern is usually
> different in that the lines tend to be parallel. Try mixing equal amounts
> of #1 and number 6 - that glaze will have a calculated expansion of about
> 385 - just combine the materials for both and divide by 2
J: The crackle pattern is fairly random, smaller-grained where thin,
larger-grained where thick. I'll try the 1&6 combination.
> EPK - 22.5
> 3134 - 22.5
> Silica - 22.5
> Custer - 10.0
> wollast - 15.0
> F4 - 7.5
> Total - 100.0
> Question #2 - How long is your firing, are you using large cones to
monitor
> the final temperature and how long do you soak at the end? Not giving the
> glaze a chance to bond well with the clay can give very small fit
> tolerances.
J: The firing for this test was 8.5 hours long. Used large cones, the 6 was
down and the 7 was just starting to curve. I'm guessing on the soak at 15-20
minutes (I have trouble holding at a certain temp- just using manual
switches- my attempts at soaking tend to make the kiln go over desired cone
temp)
> Question #3 How fast is your cooling from dull red heat to kiln opening?
If
> a glaze is cooled fast from say opening your kiln too soon you can get
> crazing - simply because the glaze cooles before the clay and contracts to
> quickly. We assume you have turned off any venting after shut off. If not
> refire all and turn vent off at end of firing.
> This may result in some of the glazes not being clear (fast cooling
promots
> clears) but if that is the case you have to turn off the vent just before
> your glazes solidify - probably around 700C
J: Don't know the answer to this. The kiln reached temp. at 4pm. I opened
it up the next morning about 6 am, so cooled for 14 hours, WITH fan vent
running the whole time. It was still warm to the touch when opening, my pyro
read 300F,
(but I don't trust the pyrometer this week, must need a new thermocouple,
readings have been way low when the cones say otherwise.)- so guessing it
could have been as hot as 500F.
So should I leave vent on until about 700C, and let kiln cool longer?
> So let me know as much as you can an we will go from there.
>
> RR
Thanks!
Jeanne S.
Jeanne Stolberg on mon 29 oct 01
Mia,
This stoneware is rated on the label as cone 06-6. I've only fired it at 4
and at 6. Once this clay is used up, I think I will look for a different
clay.
In the meantime, I have received excellent suggestions to try
Thanks,
Jeanne S. in Sitka
----- Original Message -----
From: Wade Blocker
To:
Sent: Sunday, October 28, 2001 6:27 PM
Subject: Re: crazing help
> Jeanne,
> Do you fire your stoneware cone 4 to 6, or is that stoneware rated for
> that range? If it is a stoneware body with a wide firing range eg cone 4
to
> 9 you will never find a glaze that fits without crazing. Make sure that
> your clay really has a maturation range from cone 4 to 6. Mia in ABQ
Wade Blocker on mon 29 oct 01
Jeanne,
the clay you describe does have a far too wide firing range. I had this
problem with a clay from Laguna that fired from cone 5 to 10. It did not
vitrify until cone 6, However I learned my lesson. All the transparent or
other glazes crazed and even cracked. Now i use a cone 4 to 6 stoneware
clay and have no problems with any of my glazes. Mia
Ron Roy on tue 30 oct 01
Aha!
Hi Jean,
The next best thing to soaking would be a slow rise to top temperature
and/or a slow cool after top temp. - so what I am saying is - turn your
switches down enough so you get slow cooling rather than higher temp. at
the end.
Lets say the bottom of your kiln is cooler over all - you would know this
if you had cones down there. So you want to slow cool for an hour AND try
to even your firing out. You have 3 switches for top middle and bottom
elements.
Turn top two switches to medium and leave the bottom on high for one hour.
If temperature rises - rethink - top two switches to low - bottom switch
says on high. Still rising (I don't think so) Two top on low and bottom on
medium.
All the time you are trying this stuff you have cones (large) on bottom,
middle and top shelves so you have some idea about what is happening.
The crazing - first try - shutting vent off at end of firing - I don't know
if the manufacture recommend s this but it would be the easiest to do. If
you glazes begin to get cloudy the cooling is too slow. In that case turn
the vent off about 800 or 700C (1500 to 1300F) - if your vent system has a
timer you will be able to set this to happen after you have done it by hand
- just keep a record of what you are doing.
You have to refire all those glazes - with a slower cool - no vent on - I'm
sure some will work - off at 4pm and open at ^am is certainly too fast - at
least in this case with that body.
For someone who just started you seem well ahead of the average.
RR
>> Question #3 How fast is your cooling from dull red heat to kiln opening?
>If
>> a glaze is cooled fast from say opening your kiln too soon you can get
>> crazing - simply because the glaze cooles before the clay and contracts to
>> quickly. We assume you have turned off any venting after shut off. If not
>> refire all and turn vent off at end of firing.
>> This may result in some of the glazes not being clear (fast cooling
>promots
>> clears) but if that is the case you have to turn off the vent just before
>> your glazes solidify - probably around 700C
>
>J: Don't know the answer to this. The kiln reached temp. at 4pm. I opened
>it up the next morning about 6 am, so cooled for 14 hours, WITH fan vent
>running the whole time. It was still warm to the touch when opening, my pyro
>read 300F,
>(but I don't trust the pyrometer this week, must need a new thermocouple,
>readings have been way low when the cones say otherwise.)- so guessing it
>could have been as hot as 500F.
>So should I leave vent on until about 700C, and let kiln cool longer?
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
David Hewitt on sat 3 nov 01
While I have no knowledge of Alpine White Clay I do have a very
successful cone 6 transparent shiny glaze which does not craze on
Potclays 1149 porcelain when fired to cone 6. I also fire this clay with
other glazes to cone 9.
If you are interested the recipe is:-
Wollastonite 82
China clay 175
Dolomite 39
Potash feldspar 39
Zinc oxide 13
Quartz 256
Lithium carbonate 12
BPS Low Exp. frit 384
----
1000
This gives an analysis of:-
K2O .03 Al2O3 .51 SiO2 4.02
Na2O .09 B2O3 .40
CaO .67 Fe2O3 .00
MgO .09
LiO2 .06
ZnO .06
Coeff. Of Exp 2.67 x 10-6 /oC English & Turner
Converting this as close I can get it using Ferro frit 3134 and EPK for
the china clay, I get the following recipe, but it may be possible to
get closer. If this interest you, therefore I come up with the following
recipe.
Wollastonite 42
EPK 332
Dolomite 40
Zinc oxide 12
Lithium carbonate 11
Quartz 272
Ferro frit 3134 291
----
1000
This gives a Coeff. Of Exp. of 3.26 x 10-6/oC English & Turner
Not quite as low as the original but may be low enough.
If you do try it I would be grateful if you would let us know how it
performed.
David
In message , Don & June MacDonald writes
>Hi Jeanne: I tried for a year to get something, anything to fit Alpine
>White Clay from Seattle. The answer I came up with is, nothing fits! I
>used this clay in a glaze class I was teaching in order to extend my own
>research, (also had the students use another clay body for test tiles so
>they could compare) and we had plenty of success with glazes fitting on
>the other body, but no success with Alpine White. The tests were done in
>both Cone 6 oxidation and Cone 6 reduction.
> I asked Seattle Potters Supply about the problem and was told to bisque
>hotter, Cone 04 or above, but then you have the problem of dipping
>glazes not going on quite as well. Too bad, its a great clay to throw.
>
>June from B.C.
>Jeanne Stolberg wrote:
>>
>> Help! Am trying to get a clear glaze to work on a white stoneware, fire=
>d to
>> range ^4-6 ox. (It's called Alpine White, from Seattle Pottery Supply).=
> Have
>> tested several clear glaze recipes, to no avail, they all craze. What
>> ingredients can I play around with - add more, or less of, to try to ge=
>t a
>> glaze that fits? These are mugs with underglaze decoration.
>> Some glazes I've tried, some from Clayart:
>>
>> 5x20 Clear:
>> 20 EPK; 20 FRit 3134; 20 Silica; 20 Custer; 20 Wollastonite
>>
>> Clear:
>> 12.5 Whiting; 12.5 EPK; 20 Neph. Sye; 25 Frit 3134; 30 Flint
>>
>> EZ Clear:
>> 50 Frit 3134; 30 EPK; 20 Silica
>>
>> Clear:
>> 30 Neph Sye; 8 Wollastonite; 21 Gerstley Borate; 31 Silica; 10 EPK
>>
>> Shiny Clear GTB-1
>> 8 Whiting; 27 Gerstley Borate; 39 Neph Sye; 8 EPK; 18 Silica
>>
>> G1214W Clear
>> 10 Wollastonite; 25 Frit 3134; 25 EPK; 25 Flint; 15 F4 Kona Feldsp=
>ar
>>
>> The last one came the closest, but still a bit crazed, maybe I should d=
>ink
>> around with that one.
>> I seem to be a glaze klutz, I sure would appreciate any advice you can =
>throw
>> my way!
>> Thank you!!
>> Jeanne, in cold, wet, rainy Sitka by the Sea, Alaska.
>>
>> _______________________________________________________________________=
>_______
>> 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@pcl=
>ink.com.
--
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP18 3DQ, UK. Tel:- +44 (0) 1633 420647
FAX:- +44 (0) 870 1617274
Web site http://www.dhpot.demon.co.uk
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