Anni Melancon on sat 27 may 06
I've been doing majolica off and on for many years in my studio and the
occasional workshop where I teach. I am having a recurrence of a glaze fit
problem I'd thought I'd solved.
I started using Anderson's Majolica, firing at 03 on Miller #20 terra cotta:
Frit 3124: 55
OM#4: 10
Flint 10
Zircopax 8
I liked the colors on the glaze, its lovely fattness, and it's surface is
less fragile than others I tested.
I thought it was working nicely, but when I started making bigger, (but
still modest sized) especially slab pieces, the glaze started shivering and
pulling my pieces apart, mostly post-firing, but some cracking in the kiln
(cooling cracks).
I made many tests and for several years used the following adaptation:
Frit 3124 69.8
Calcined china clay 12.7
Flint 17.5
zircopax: 10.0
Bentonite 1.0
I also started using FLOCs to my water for great suspension. This worked
for several years, then suddenly had great cracking apart problems again (in
a workshop, sadly) even on smaller pieces (again, after the firing, one
broke in the kiln). The pieces were fired in 2 different kilns, to cone 03.
My majolica buddy Dale, told me she'd been having problems and switched clay
to Sheffield #10714NG. I tried it, loved how it worked and fired, made some
pots last December, they came out fine.
I just fired some more things: one plate's glaze is shivering off its
rounded rim, and a small slab built butter dish is cracking. There's been
alot of dinging and ringing coming from the shelves!
I called Dale who has thrown in the majolica towel. I'm about to start
glaze tests again, and would sure like your best advice and opinions! I'm
so depressed, and this is what I'm making while in studio transition and
don't have my gas kiln re-built yet.
also: I have some groggy terra cotta that I want to use up and fire up
quickly and be done with: any suggestions on a commercial white or black
glaze which can be poured and dipped? like amaco, etc?
thank you anyone!
Anni
Elizabeth Priddy on sun 28 may 06
also: I have some groggy terra cotta that I want to
use up and fire up
quickly and be done with: any suggestions on a
commercial white or
black
glaze which can be poured and dipped? like amaco,
etc?
_____________________________________
I use Minnesota clay "slate black" which is semi-matte
and c 05, it has a subtle silvery sheen
It can be poured dipped and brushed.
Elizabeth Priddy
Beaufort, NC - USA
http://www.elizabethpriddy.com
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Ron Roy on tue 30 may 06
Hi Anni,
What a lousy situation to be in -
The first glaze only adds to 83 so I have to ask if it's right?
The second glaze is strange - calcined kaolin and bentonite? Is it hard to
keep stirred?
Both glazes have a rather low calculated expansion rate - so I am not
surprised that they would shiver on some clay bodies. Send me any more
glazes you get and I will check them out for you.
The first thing to do is go to your clay supplier and tell them what is
happening - they may have changed the clay formulation - if so tell em you
want it the way it was before - when it worked properly.
By the way - speed of firing is an important factor - especially with low
fire work. You need to give enough time for the glaze to get well bonded to
the clay. Fast firing - especially at the end of the glaze fire - can make
for poorly bonded glazes that can produce those kind of fit problems.
>I started using Anderson's Majolica, firing at 03 on Miller #20 terra cotta:
>Frit 3124: 55
>OM#4: 10
>Flint 10
>Zircopax 8
>
>I liked the colors on the glaze, its lovely fattness, and it's surface is
>less fragile than others I tested.
>
>I thought it was working nicely, but when I started making bigger, (but
>still modest sized) especially slab pieces, the glaze started shivering and
>pulling my pieces apart, mostly post-firing, but some cracking in the kiln
>(cooling cracks).
>
>I made many tests and for several years used the following adaptation:
>Frit 3124 69.8
>Calcined china clay 12.7
>Flint 17.5
>zircopax: 10.0
>Bentonite 1.0
>
>I also started using FLOCs to my water for great suspension. This worked
>for several years, then suddenly had great cracking apart problems again (in
>a workshop, sadly) even on smaller pieces (again, after the firing, one
>broke in the kiln). The pieces were fired in 2 different kilns, to cone 03.
>
>My majolica buddy Dale, told me she'd been having problems and switched clay
>to Sheffield #10714NG. I tried it, loved how it worked and fired, made some
>pots last December, they came out fine.
>I just fired some more things: one plate's glaze is shivering off its
>rounded rim, and a small slab built butter dish is cracking. There's been
>alot of dinging and ringing coming from the shelves!
>
>I called Dale who has thrown in the majolica towel. I'm about to start
>glaze tests again, and would sure like your best advice and opinions! I'm
>so depressed, and this is what I'm making while in studio transition and
>don't have my gas kiln re-built yet.
>
>also: I have some groggy terra cotta that I want to use up and fire up
>quickly and be done with: any suggestions on a commercial white or black
>glaze which can be poured and dipped? like amaco, etc?
>
>thank you anyone!
>Anni
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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