nancy patterson on mon 29 dec 03
Happy New Year All!
I have a question, or a few about matte glazes.
I don=B9t have much experience mixing my own glazes
and have only used the mastering cone 6 glazes book with great results
with the licorice and sky blue and they work great together!
I cannot get a good matte I have used the programmed firing
slow cool firing ramp as directed. Does anyone have any other ^6
matte recipes or tips? And is it possible to have a piece with both matte
and glossy
glazes...actually I know it is possible because I have seen them, but how i=
s
it done
if glossy glazes are fast or naturally cooled and matte are slow cooled.
I am confused? or am I wrong?
Thanks all!
I don=B9t know what I=B9d do without all the information
I get from this list and am grateful to all.
Peace,
Nancy
Paul Lewing on mon 29 dec 03
on 12/28/03 9:01 PM, nancy patterson at potter@NYC.RR.COM wrote:
> And is it possible to have a piece with both matte
> and glossy
> glazes...actually I know it is possible because I have seen them, but how i=
> s
> it done
> if glossy glazes are fast or naturally cooled and matte are slow cooled.
> I am confused? or am I wrong?
You're not wrong, Nancy, it's just that that's not all of the story. While
the cooling rate is important and slow cooling can make a glaze that was
glossy when cooled fast into a matte glaze, the chemistry of the glaze
itself is equally important. What determines the surface quality more than
anything else is the ratio of alumina to silica. Glazes with lots of silica
and not much alumina tend to be glossy, and those with lots of alumina and
not much silica tend to be matte. If a glaze has a Si:Al ratio of 12:1 no
amount of slow cooling is going to make it matte. Conversely, a glaze with
a ratio of 3:1 is going to be matte no matter how you fire it.
Paul Lewing, Seattle
sdr on mon 29 dec 03
.........I cannot get a good matte I have used the programmed firing
slow cool firing ramp as directed. Does anyone have any other ^6
matte recipes or tips.......>>>
There are a lot of good cone 6 matte glazes. Get Val Cushing's
handbook; he has a number of them in there, and many are very
good indeed.
Matte glazes are not necessarily good liner glazes for functional
wares (they tend to mar, and may not be as stable as the harder
more "glassy" glazes). But they are not difficult to achieve, and
can be used in concert with gloss glazes. Experiment. Take a
bit of time. It truly takes practice to find what works for you and
your clay. And your esthetic.
regards
Dannon Rhudy
John Hesselberth on mon 29 dec 03
On Monday, December 29, 2003, at 12:01 AM, nancy patterson wrote:
> I don=92t have much experience mixing my own glazes
> and have only used the mastering cone 6 glazes book with great results
> with the licorice and sky blue and they work great together!
> I cannot get a good matte I have used the programmed firing
> slow cool firing ramp as directed. Does anyone have any other ^6
> matte recipes or tips?
Hi Nancy,
First be sure you are not firing the glazes in the book over cone 6.=20
This means when you open the kiln after it has cooled, cone 6 should be=20=
almost tip touching. If you are letting your computer decide what is=20
cone 6 instead of verifying it with cones that could be your problem.=20
The calibration of thermocouples can easily be off a cone or two.
Second, slowing down the cooling even more. I have now dropped to 125=20
deg F /hr from 1900 down to 1400 (I cool quickly from peak temperature=20=
to 1900 after I complete a 15 minute soad. Try a test firing even=20
slower than that. If you cool as slowly as 50-75 deg/hr through that=20
temperature range you can get a quite dry matte from the high calcium=20
semimattes that are in the book. Of course the two glazes you=20
referenced in your note are not formulated to be matte even if cooled=20
slowly.
There are plenty of other mattes out there; however, quite a number of=20=
them are 'unmelted mattes' and are not very durable. If you are making=20=
functional work it is worth some additional effort to make sure you are=20=
working with durable glazes.
Good luck,
John
http://www.frogpondpottery.com
http://www.masteringglazes.com
Ron Roy on wed 31 dec 03
Hi Nancy,
I agree with what Paul says but - there are a couple of bits of info that
may make it more understandable.
There are other kinds of matte glazes besides high alumina mattes. As you
will see in our book - in order to get stable matte glazes you need to get
a good melt - so high calcium glazes are an option - and I suspect the same
with some other of the earth alkalies like strontium and magnesium. I'm
sure zinc would fit in there as well.
In other words too much of them would give you a matte glaze with a slow
cool and there are other glazes that will not recrystallize with that same
cooling.
I believe most of the glazes we use will recrystallize if cooled slow
enough - like days or weeks - just a matter of time.
The short answer is yes - just do the testing till you find two you like
and find a way to get em on your pots so they look pleasing to you. Any
over lap will tend to be on the shiny side.
RR
>> And is it possible to have a piece with both matte
>> and glossy
>> glazes...actually I know it is possible because I have seen them, but how i=
>> s
>> it done
>> if glossy glazes are fast or naturally cooled and matte are slow cooled.
>> I am confused? or am I wrong?
>You're not wrong, Nancy, it's just that that's not all of the story. While
>the cooling rate is important and slow cooling can make a glaze that was
>glossy when cooled fast into a matte glaze, the chemistry of the glaze
>itself is equally important. What determines the surface quality more than
>anything else is the ratio of alumina to silica. Glazes with lots of silica
>and not much alumina tend to be glossy, and those with lots of alumina and
>not much silica tend to be matte. If a glaze has a Si:Al ratio of 12:1 no
>amount of slow cooling is going to make it matte. Conversely, a glaze with
>a ratio of 3:1 is going to be matte no matter how you fire it.
>Paul Lewing, Seattle
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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