Cindy Strnad on fri 9 feb 01
Hello, Alisa.
Reading your post on Tony Hansen's matte base and the Waxy White Liner
glaze, I'm wondering about your cooling cycle. I've used Tony's matte base
and gotten a nice buttery matte with a slight tendency toward shallow
pinholes. I haven't tested all the colorants you have, but I got a subdued
medium-dark blue on brown clay. I haven't tried the Waxy White yet. I'm
happy with the other mattes I've been working with, and as they don't
contain Gerstley . . . .
Anyway, with either Tony's or Ron's matte bases, the reason you get a matte
finish is the formation of calcium crystals. For this, you need a slow
cooling cycle. I've been cooling at 100 Fahrenheit per hour down to 1000
degrees F., but this is probably overkill. It's just been too cold to stay
in the kiln building long enough to enter a different ramp program.
Of course, coloring oxides will flux the glaze a bit, and the more you add,
the glossier the glaze will be.
Another thing to think about with the Waxy White . . . when you're mixing a
test batch, any little thing you do differently can make a large impact on
the finished glaze. When you're mixing a larger batch, these little
inaccuracies are mostly canceled out. So I wonder whether the original glaze
might have been nicer because you measured something slightly over or under
the quantities called for?
Here's another waxy matte glaze I've been playing with recently. It hasn't
been safety tested or anything, and I haven't used it long enough to vouch
for it, but it does look nice--a medium dark blue--with 2% cobalt oxide.
I'll be doing vinegar tests and crazing tests and all, but haven't done them
yet.
Crystal Matte ^6 *Requires a slow cool*
EPK KAOLIN 30
WHITING 21
CUSTER FELDSPAR 20
FRIT 3134 15
SILICA 14
This glaze came about because I wanted to use Ron's matte base for blue. I
chose not to use Tony's because of the tendency to pinhole. But, with Ron's
base, the glaze was closer to a baby blue, and I wanted dark. So I fiddled
around with it to bring the numbers nearer to those in Tony's glaze, and
this is what I came up with. And, lucky me! No pinholes so far. Cross your
fingers.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
Wade Blocker on fri 9 feb 01
Alisa, The thickness of your glaze application has a lot to do with the
final result. A few degrees hotter or colder in your glaze firing also
makes a difference. Mia in sunny ABQ
Alisa og Claus Clausen on fri 9 feb 01
Dear Clayart,
I am troubled by a glaze that Marcia Selsor contributed.
The receipe is for Waxy White liner, cone 6.
Receipe
20 G.B.
30 Neph. Sye
13.3 EPK
9.4 Whiting
17.4
10 Silica
15 Zirocpax
The first test was successful, producing an opaque, waxy white matt, one =
I wanted to add to my glaze palette.
I mixed up 5000 grams, fired one larger piece with it, and it fired to a =
slightly yellow
gloss.
I have made two tests since in two different firings and they both show =
whitish yellowish gloss, transparent. I colored it with about 1% cobalt =
and luckily that gave a nice but glossy greyish blue.
I have not used witness cones in the last few firings, although my =
electronic controller shows 1220c and a soak of 15 minutes, as usual.
What could be the change from the first good test to the unsuccess of =
the later firings? I have not refilled any supplies since the first =
test.
Best regards,
Alisa in Denmark
Ron Roy on sun 11 feb 01
Hi Alisa,
I am trying to check your glaze to see if there is an answer there but you
have left a material out - 17.4 what?
Do you know how to check your scales? It's very important wnen doing small
tests to be very accurate so the larger batch will look the same. It is
especially important if the glaze is out of limits - unbalanced - that is
what I was trying to check.
RR
>I am troubled by a glaze that Marcia Selsor contributed.
>The receipe is for Waxy White liner, cone 6.
>
>Receipe
>20 G.B.
>30 Neph. Sye
>13.3 EPK
>9.4 Whiting
>17.4
>10 Silica
>15 Zirocpax
>
>The first test was successful, producing an opaque, waxy white matt, one I
>wanted to add to my glaze palette.
>
>I mixed up 5000 grams, fired one larger piece with it, and it fired to a
>slightly yellow
>gloss.
>
>I have made two tests since in two different firings and they both show
>whitish yellowish gloss, transparent. I colored it with about 1% cobalt
>and luckily that gave a nice but glossy greyish blue.
>
>I have not used witness cones in the last few firings, although my
>electronic controller shows 1220c and a soak of 15 minutes, as usual.
>
>What could be the change from the first good test to the unsuccess of the
>later firings? I have not refilled any supplies since the first test.
>
>Best regards,
>Alisa in Denmark
>
>______________________________________________________________________________
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>
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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
Tony Hansen on sun 18 feb 01
Even more than our 20 x 5 recipe, we impress on everyone using our matte cone 6
recipe that it requires fine tuning by each person using it. It has its own
lengthy web
page that describes the challenges of making a good matte glaze. Matte
glazes of this
type have to have non-fluid melts, that means more problems with pinholes and
blistering than with other types of glazes. However you can compromise,
reducing
the alumina to get more fluidity at the expense of some of the
matteness. There
are a host of other things you can do also, our web site has long pages
that outline
tons of things you can do to fix pinholes and blistering. All of these
pages are
accessible at http://digitalfire.com/education/glaze
Also, you can make magnesia mattes using Gerstley Borate (or should I say
Boraq) that
are as good or better than their cone 10 counterparts. Check it out on the
Boraq
page at www.gerstleyborate.com.
====================================================
T o n y H a n s e n thansen@digitalfire.com
D I G I T A L F I R E C O R P O R A T I O N
http://digitalfire.com Calculation/Database Software for Ceramic Industry
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