Scott James on sat 22 may 99
I am still trying to find a good ^5 transparent. I have tested several now,
but none quite there. The most promising so far is the 5x20 from
www.digitalfire.com but it is slightly milky instead of clear. It also
crazed 1 day after coming out of the kiln (it was fine the night I took out
the test tiles and the next morning, but crazed by that afternoon.) Any
ideas on where I need to go with this? I don't know if this matters, but I
did open the kiln at about 150 degrees and removed the tiles fairly soon
after. They were warm, but not too hot. Would this cause the crazing? My
thinking is that if it is to withstand oven or microwave use, it should
withstand 150 degrees to 70 degree shock. right? Honestly though, I was
just anxious to see how things went. :-)
The glaze is as follows.
20 wollastonite
20 ferro frit 3134
20 epk kaolin
20 custer feldspar
20 silica
I want to get to something crystal clear and no crazing. I'm new to glaze
formulation and chemistry, but am reading tons to try and learn as fast as I
can. would the milkiness in the color be caused by too slow of cooling
(crystal formation ?) I don't think it is going too slowly though -- about
20 to 24 hrs from ^5 temperature to 150 degrees. My other thought, is that
it may need to be fired to ^6? But I am worried about my underglazes
burning out. Which by the way looked great!! Thanks for all the help
everyone gave me with them!
Here is the Unity formula that I have for this if that will help.
Na2O .14
K2O .07
CaO .79
Al2O3 .36
B2O3 .21
SiO2 3.37
Thanks,
Scott j.
amy parker on sat 22 may 99
At 09:24 AM 5/22/99 EDT, you wrote:
>----------------------------Original message----------------------------
>I am still trying to find a good ^5 transparent. I have tested several now,
>but none quite there. The most promising so far is the 5x20 from
>www.digitalfire.com but it is slightly milky instead of clear. It also
>crazed 1 day after coming out of the kiln
I have been using the G1214W from digitalfire.com with excellent results.
No crazing, even on my porcelain body. It is clearer than any other glaze
I have tested, although it you leave thick spots it will be milky. I use it
over a variety of Amaco Velvet Underglazes, and the only milkiness is as I
said, where it is thick. Try adding a little more water - Tony recommends
equal weight of water to dry ingredients for this - 1 liter = 1000 gms - I
just use the measuring cup rather than trying to weigh water.
amy parker Lithonia, GA
amyp@sd-software.com
David & Diane Chen on sun 23 may 99
Scott, go a little further in the digitalfire site. There is a glaze using
wollastonite, frit 3195, flint, and I can't remember the last one but it is
in the same place you found the 5x20 glaze. I have found it to be more
transparent than the 5 20's.
diane
massachusetts
Barney Adams on sun 23 may 99
The CaO is pretty high and I would imagine could cause some
milkiness. I like the melt of adding some strontium carb with
the added benefit of getting rid of pinholes. I havent tested this for
clear and I'm assuming you are using stoneware.
Untitled Recipe 1
=================
FRIT 3134........... 20.00 20.00%
EPK KAOLIN.......... 20.00 20.00%
CUSTER FELDSPAR..... 20.00 20.00%
SILICA.............. 20.00 20.00%
STRONTIUM CARBONATE. 13.00 13.00%
TALC................ 7.00 7.00%
========
100.00
CaO 0.29* 5.06%
MnO2 0.00 0.01%
MgO 0.18* 2.29%
K2O 0.08* 2.26%
Na2O 0.15* 2.91%
Fe2O3 0.00 0.21%
TIO2 0.00 0.06%
B2O3 0.23 4.98%
AL2O3 0.37 11.82%
SiO2 3.22 60.53%
P2O5 0.00 0.03%
SrO 0.30* 9.84%
COST/KG 3.10
Si:Al 8.70
SiB:Al 9.32
EXPAN452.09
For a good melt I might even try to add a very small amount of Zinc
Oxide
(no more than 2%) just to give more variation in the melt. You could try
lowering the strontium to accomadate.
Having a range of fluxes that kick in at diffrent times during the
firing
cycle seems to give a nice melt and allow a high amount of silica and
Al2O3.
Unless of course Ron or Tom say I'm full of it....
I tend to like to keep things simple, but I've been having better luck
going
with a complex recipe in terms of the range of fluxes.
Barney
Scott James wrote:
>
> ----------------------------Original message----------------------------
> I am still trying to find a good ^5 transparent. I have tested several now,
> but none quite there. The most promising so far is the 5x20 from
> www.digitalfire.com but it is slightly milky instead of clear. It also
> crazed 1 day after coming out of the kiln (it was fine the night I took out
> the test tiles and the next morning, but crazed by that afternoon.) Any
> ideas on where I need to go with this? I don't know if this matters, but I
> did open the kiln at about 150 degrees and removed the tiles fairly soon
> after. They were warm, but not too hot. Would this cause the crazing? My
> thinking is that if it is to withstand oven or microwave use, it should
> withstand 150 degrees to 70 degree shock. right? Honestly though, I was
> just anxious to see how things went. :-)
>
> The glaze is as follows.
> 20 wollastonite
> 20 ferro frit 3134
> 20 epk kaolin
> 20 custer feldspar
> 20 silica
>
> I want to get to something crystal clear and no crazing. I'm new to glaze
> formulation and chemistry, but am reading tons to try and learn as fast as I
> can. would the milkiness in the color be caused by too slow of cooling
> (crystal formation ?) I don't think it is going too slowly though -- about
> 20 to 24 hrs from ^5 temperature to 150 degrees. My other thought, is that
> it may need to be fired to ^6? But I am worried about my underglazes
> burning out. Which by the way looked great!! Thanks for all the help
> everyone gave me with them!
>
> Here is the Unity formula that I have for this if that will help.
> Na2O .14
> K2O .07
> CaO .79
> Al2O3 .36
> B2O3 .21
> SiO2 3.37
>
> Thanks,
> Scott j.
Pottery by Dai on sun 23 may 99
Hi, Scott - Before you try adding or subtracting percentages of glaze
materials to get a glaze more to your liking, try a slightly thinner coat of
glaze on your pieces. I have a clear recipe that, if applied too thickly,
will be milky, and also promotes crazing. When I dip more quickly, or thin
the glaze out a bit, there are no problems. Good luck!
Dai Scott - Kelowna, B.C.
P.S. If that doesn't work for the crazing, I understand an addition of
silica may stop that---maybe start with 5% more and work up from there till
the problem is solved.
Antoinette Badenhorst on mon 24 may 99
Hi, Amy. I went through my South African recipes to see if I can find
something that might help you. I came across an earthenware transparent
(1100 Celsius) which was used by Sarie Maritz. The comments says
dip,spray or sponge on - thin. A clear glaze!
Lead Bisilicate 65
Feldspar (in SA normally Potash) 15
Kaolin 10
Silica 5
Whiting 5
SA kaolins contain little or no iron.
Delute transparent glazes thinner than other glazes to prevent crazing
.
Hope this help.
Regards.
Antoinette.
--- amy parker wrote:
> ----------------------------Original
> message----------------------------
> At 09:24 AM 5/22/99 EDT, you wrote:
> >----------------------------Original
> message----------------------------
> >I am still trying to find a good ^5 transparent. I
> have tested several now,
> >but none quite there. The most promising so far is
> the 5x20 from
> >www.digitalfire.com but it is slightly milky
> instead of clear. It also
> >crazed 1 day after coming out of the kiln
>
> I have been using the G1214W from digitalfire.com
> with excellent results.
> No crazing, even on my porcelain body. It is
> clearer than any other glaze
> I have tested, although it you leave thick spots it
> will be milky. I use it
> over a variety of Amaco Velvet Underglazes, and the
> only milkiness is as I
> said, where it is thick. Try adding a little more
> water - Tony recommends
> equal weight of water to dry ingredients for this -
> 1 liter = 1000 gms - I
> just use the measuring cup rather than trying to
> weigh water.
> amy parker Lithonia, GA
> amyp@sd-software.com
>
===
Antoinette Badenhorst
PO Box 552
Saltillo,Mississippi
38866
Telephone (601) 869-1651
timakia@yahoo.com
_____________________________________________________________
Do You Yahoo!?
Free instant messaging and more at http://messenger.yahoo.com
amy parker on tue 25 may 99
I don't think a 65% LEAD glaze is acceptable for ANYTHING!!!
Amy in Atlanta, who can't believe anyone who reads this list would post
such a thing!!! Are you asleep out there? Is Sarie Maritz still alive?
What about the pottery users!!
At 09:54 AM 5/24/99 EDT, you wrote:
>----------------------------Original message----------------------------
>Hi, Amy. I went through my South African recipes to see if I can find
>something that might help you. I came across an earthenware transparent
>(1100 Celsius) which was used by Sarie Maritz. The comments says
>dip,spray or sponge on - thin. A clear glaze!
>
>Lead Bisilicate 65
>Feldspar (in SA normally Potash) 15
>Kaolin 10
>Silica 5
>Whiting 5
>
>
>SA kaolins contain little or no iron.
>Delute transparent glazes thinner than other glazes to prevent crazing
>.
>Hope this help.
>Regards.
>Antoinette.
>
>--- amy parker wrote:
>> ----------------------------Original
>> message----------------------------
>> At 09:24 AM 5/22/99 EDT, you wrote:
>> >----------------------------Original
>> message----------------------------
>> >I am still trying to find a good ^5 transparent. I
>> have tested several now,
>> >but none quite there. The most promising so far is
>> the 5x20 from
>> >www.digitalfire.com but it is slightly milky
>> instead of clear. It also
>> >crazed 1 day after coming out of the kiln
>>
>> I have been using the G1214W from digitalfire.com
>> with excellent results.
>> No crazing, even on my porcelain body. It is
>> clearer than any other glaze
>> I have tested, although it you leave thick spots it
>> will be milky. I use it
>> over a variety of Amaco Velvet Underglazes, and the
>> only milkiness is as I
>> said, where it is thick. Try adding a little more
>> water - Tony recommends
>> equal weight of water to dry ingredients for this -
>> 1 liter = 1000 gms - I
>> just use the measuring cup rather than trying to
>> weigh water.
>> amy parker Lithonia, GA
>> amyp@sd-software.com
>>
>
>
>
>===
>Antoinette Badenhorst
>PO Box 552
>Saltillo,Mississippi
>38866
>Telephone (601) 869-1651
>timakia@yahoo.com
>_____________________________________________________________
>Do You Yahoo!?
>Free instant messaging and more at http://messenger.yahoo.com
>
>
amy parker Lithonia, GA
amyp@sd-software.com
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