Cindy Strnad on tue 23 jan 01
Jocelyn,
Zinc is a bugger. You could sieve it dry, then calcine it, but maybe someone
will have a better idea. Dry sieving is no fun--as bad as sanding. If you
decide to try this, do it outside with a proper mask.
If you're not losing gobs of it, you may be okay just writing off the zinc
that gets left in the sieve. I do this with wollastonite, but I have no idea
what it will do to your zinc glazes, especially as I can't see how much of
the stuff you're losing.
Another idea might be to mix the zinc separately, into hot water. I use a
hand-held blender to mix my test glazes. It doesn't get all the lumps, but
it does seem to help.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
Jocelyn McAuley on tue 23 jan 01
Hello all,
After much information gathering and anticipation I've finally started
testing some of my gathered macro crystalline glazes... and have come up
against a couple walls! I could really use some help and advice.
My first problem was in seiving my glazes. I really don't want to
ballmill my tests, but even after attacking my calcined zinc with a mortar
and pestle, I can't get all of it through an 80s. I ended up using a tea
strainer (which appeared to have worked ok). Is this normal with zinc
oxide, or is it something that comes with a really old batch of it?
My next problem came with programming the Skutt at school. Even following
their suggested crystalline program, I came up against err 2, which I
believe is "the program is in hold and the temperature is 50 degrees or
more above the hold temperature". I tried running miniature fires going
up to 150 degrees to test the "9999" I used for the ramp. They didn't
seem to indicate much...
Here is the crystalline firing program
I tried:
1 200 degrees/hr to 1652, 0 hold
2 400 degrees/hr to 2300, 0 hold
3 9999 to 2000, 1:30
4 9999 to 1950, 1:30
5 9999 to 1930, 1:30
6 9999 to 1900, 0:10
Was I expecting too much out of my kiln? I really didn't want to have to
resort to physical intervention with the kiln (cracking the lid, etc).
Next firing, this weekend, I am going to babysit the firing the entire
way. Some way or another I am going to force it to stick with my holds!
Here are the glaze recipes I am testing this week
Cone 9 Dan Turnidge Base II
Ferro frit 3110 49.1%
Zinc Oxide* 22.6%
Silica 22.6%
Titanium Dioxide 5.7%
Bentonite 2.0%
Cone 9 Dan Turnidge Base I
Ferro frit 3110 50.0%
Zinc Oxide* 24.7%
Silica 19.6%
Kaolin* 0.5%
Titanium Dioxide 5.2%
Bentonite 2.0%
thank you so much for your help!
--
Jocelyn McAuley ><<'> jocie@worlddomination.net
Jeff Lawrence on wed 24 jan 01
Jocelyn was wondering about her crystalline glaze firing regimen
Hi Jocelyn,
I have a Skutt and vaguely remember that Err2 on it means you're asking it
to go higher than it can go. I discovered this when I tried to fire my cone
8 model to cone 10. It didn't reach temperature but it did wear out the
elements trying! I subsequently got Err2 at lower and lower temps until I
had to change the elements. Maybe your elements are tired.
My limited experience suggests that some truisms need to be questioned:
1. the speed of the ramp and crash of the cool may not be as important as
the literature indicates.
2. the glaze doesn't seem to need the thickness that many sources recommend.
I've been having fair success with meandering up to temp at 100-150C per
hour, soaking there for 1/2 hour, then down to a soak for 5 hours. I finally
managed to resist adding the temperature spikes until I know what I'm doing.
Here is what I'm doing at cone 6:
1 90C/hr to 90C, hold 2:00
2 100C/hr to 400C, hold 2:00 (first two ramps for single-fire sake)
3 150C/hr to 1225C, hold 0:20 (but my wimpy cone 6 bodies bloated here)
4 200C/hr to 1025C, hold 5:00
I got crystals up to 2" diameter -- thicker glaze made for more crystals.
Also, different glaze bases seemed to notice small diffs in temp as far as
crystal growth goes.
I sprayed a thin coating to avoid overmuch flow -- two moderate coats with
the sprayer. As long as it melted, crystals grew.
Jeff Lawrence ph. 505-753-5913
18496 US HWY 84/285 fx. 505-753-8074
Espanola, NM 87532 jml@cybermesa.com
Brad Sondahl on wed 24 jan 01
Zinc accumulates water from the air. It should be kept in a plastic bag
with a tightly tied twistem to avoid lumping. Once lumpy, it's
definitely hard to get through sieves. You could try blending the wet
mix in a blender before sieving, if the batch isn't too big. If most of
the material will pass through the sieve, the big stuff at the end
should be discardable without affecting the glaze.
I don't use a programmable kiln, so can't help on that--however, as
attested on my webpage, initial temperature reached seems to be as
critical as holding at certain temperatures to achieve crystalline
glazes. I never hold on the way down--just use a kilnsitter shutoff,
and the results mostly vary according to glaze thickness and peak
temperature reached.
Brad Sondahl
--
For original art, music, pottery, and literature, visit my homepage
http://pages.about.com/bsondahl
Pottery homepage http://sondahl.safeshopper.com
william schran on thu 25 jan 01
Jocelyn - Sounds like the zinc has gotten wet or absorbed moisture,
I'd suggest calcining. I don't use a controller for my crystalline
glazes, but when in doubt, contact the manufacturer.
Bill
Leonard & Ronise Powalski on thu 25 jan 01
Hi Jocelyn,
This is Roni from Austin Texas. I've worked with crystalline a bit a couple
of years ago. I didn't
have a programable kiln but had a pyrometer. First thing, the size of the
crystals will depend
on the clay body. Porcelin being the best. I've tried crystal firings on
B-mix and Balcones white
that we get here in Texas. I can get about a one inch crystal on both of
these clay bodies using
receipe : Crebers ^ 9
Frit 3110 48.4
Zinc 24.4
EPK 1.5
Silica 17.9
Add 3 to 5% Titanium Dioxide
Add 1.1% Lithium Carb
Add 2.2% Bentonite
Play around with the oxides. Rutile can do some nice stuff too.
My friend has tested this on porcelin slip ware ^ 9 and got huge crystals.
I fired as follows: Fire to 2300 F, Rapidley cool to 2050. Just take out
the plugs on your kiln.
This stops the flow of glaze so that the crystals can begin to grow. Hold
for 2 hours.
Then drop to 1980 hold for two more hours, then turn off. I've had pretty
good results with this
method.
Did you get any crystalls developing ? If so what size were they?
Zinc Oxide often lumps up. Sift it before putting it into your receipe.
Some of the lumps my
be too big to break up.
Good Luck
roni
----- Original Message -----
From: Jocelyn McAuley
To:
Sent: Tuesday, January 23, 2001 12:49 PM
Subject: Crystalline help / kiln programming
> Hello all,
>
> After much information gathering and anticipation I've finally started
> testing some of my gathered macro crystalline glazes... and have come up
> against a couple walls! I could really use some help and advice.
>
> My first problem was in seiving my glazes. I really don't want to
> ballmill my tests, but even after attacking my calcined zinc with a mortar
> and pestle, I can't get all of it through an 80s. I ended up using a tea
> strainer (which appeared to have worked ok). Is this normal with zinc
> oxide, or is it something that comes with a really old batch of it?
>
>
> My next problem came with programming the Skutt at school. Even following
> their suggested crystalline program, I came up against err 2, which I
> believe is "the program is in hold and the temperature is 50 degrees or
> more above the hold temperature". I tried running miniature fires going
> up to 150 degrees to test the "9999" I used for the ramp. They didn't
> seem to indicate much...
>
> Here is the crystalline firing program
> I tried:
>
> 1 200 degrees/hr to 1652, 0 hold
> 2 400 degrees/hr to 2300, 0 hold
> 3 9999 to 2000, 1:30
> 4 9999 to 1950, 1:30
> 5 9999 to 1930, 1:30
> 6 9999 to 1900, 0:10
>
> Was I expecting too much out of my kiln? I really didn't want to have to
> resort to physical intervention with the kiln (cracking the lid, etc).
> Next firing, this weekend, I am going to babysit the firing the entire
> way. Some way or another I am going to force it to stick with my holds!
>
> Here are the glaze recipes I am testing this week
>
> Cone 9 Dan Turnidge Base II
> Ferro frit 3110 49.1%
> Zinc Oxide* 22.6%
> Silica 22.6%
> Titanium Dioxide 5.7%
>
> Bentonite 2.0%
>
> Cone 9 Dan Turnidge Base I
> Ferro frit 3110 50.0%
> Zinc Oxide* 24.7%
> Silica 19.6%
> Kaolin* 0.5%
> Titanium Dioxide 5.2%
>
> Bentonite 2.0%
>
>
>
> thank you so much for your help!
>
>
> --
> Jocelyn McAuley ><<'> jocie@worlddomination.net
>
>
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melpots@pclink.com.
>
>
ferenc jakab on fri 26 jan 01
> If you're not losing gobs of it, you may be okay just writing off the zinc
> that gets left in the sieve. I do this with wollastonite, but I have no
idea
> what it will do to your zinc glazes, especially as I can't see how much of
> the stuff you're losing.
One word with Zinc------- Ball Mill. ............. O.k. It's two words. A
mortar and pestle is also a (poor) substitute.
Feri.
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