Imbolchottie@AOL.COM on thu 16 sep 04
I was going over the last couple hundred posts looking to see if anyone had
been working with the 20x5, Tony Hansen's glaze. There I found Neal -- and you
know, I don't have a problem with it crazing. After reading John's reply, I
have to hit the books and see if I can catch up with you guys. I still have
yet to master glaze calculations.
My question about the 20x5 is how to make it into a matte. Has anyone tried?
I'm using Bmix w/ grog (B-G) and it is a good match glaze/clay. What I
thought was sorta funny (after two days of gnashing my teeth & kicking furniture)
is that I lost 3/4's of a kiln due to the crawling of the High Calcium Semi
Matte from John & Ron's book. (MC6G)
I've tried a variety of ways of applying and firing and I must have mixed it
incorrectly. That's the only thing I can think of. I made it before and it
has a great feel to it and I thought -- ok, I finally have a matte and a gloss
that I can rely on. So I'm putting this down to human error.
That may sound like a general, or broad statement, but I have been testing
the sample box of browns, red and terra cotta clays from Laguna. I took one box
and made 90 test tiles - 10 of each clay -- and I tested all of my stable
glazes on them to see how the fit was, which was best, which ones really suck.
You can spot my goofed up glaze (HCSM -2) -- At least it was consistently
crawling on all nine tiles.
The other box I took and threw three pieces from each sample. These I will
be using for a reduction sample firing.
I'm learning the GlazeChem program slowly thanks to Holly in PA, but
reworking a glaze from glossy to matte is out of my league at this point -- any help
would be great.
Jonathan in LA
GQ meets a brick wall: brick wall 2, GQ - 0
Chris Schafale on fri 17 sep 04
Jonathan,
Tony had a matte glaze base on his site -- go to www.digitalfire.com -- but
don't give up on the MC6G recipe too soon.
One thing that is true of a lot of matte glazes is that they have more
clay, to give you a lower Si:Al ratio. Unfortunately, having a lot more
clay can lead to crawling because it causes the glaze to shrink more as it
dries on the pot. Sometimes you only see the problem when you apply the
glaze to actual pots, because test tiles tend to be thinner and thus take
up less glaze. So your test tiles and even small pots look great, but when
you mix up a 5000 gram batch and commit a whole kiln load of real work,
then you suddenly get crawling and the resultant tearing of hair, gnashing
of teeth, and kicking of furniture. (Can you tell I have been there, done
that?? I have a closet in my studio labelled: "The Outer Darkness, where
there is weeping and gnashing of teeth, and lots of Really Bad Pots")
I had a horrendous time with crawling when I first started mixing glazes,
and what finally fixed it was a combination of bisquing to 06 instead of 04
so my pots are more absorbent, and subbing part calcined clay so that I
never have more than 15% raw clay in a recipe. Ron prefers subbing ball
clay for EPK, but this never worked for me.
Good luck
Chris
At 9/16/2004 11:53 PM, you wrote:
>I was going over the last couple hundred posts looking to see if anyone had
>been working with the 20x5, Tony Hansen's glaze. There I found Neal --
>and you
>know, I don't have a problem with it crazing. After reading John's reply, I
>have to hit the books and see if I can catch up with you guys. I still have
>yet to master glaze calculations.
>
>My question about the 20x5 is how to make it into a matte. Has anyone tried?
> I'm using Bmix w/ grog (B-G) and it is a good match glaze/clay. What I
>thought was sorta funny (after two days of gnashing my teeth & kicking
>furniture)
>is that I lost 3/4's of a kiln due to the crawling of the High Calcium Semi
>Matte from John & Ron's book. (MC6G)
>
>I've tried a variety of ways of applying and firing and I must have mixed it
>incorrectly. That's the only thing I can think of. I made it before and it
>has a great feel to it and I thought -- ok, I finally have a matte and a gloss
>that I can rely on. So I'm putting this down to human error.
>
>That may sound like a general, or broad statement, but I have been testing
>the sample box of browns, red and terra cotta clays from Laguna. I took
>one box
>and made 90 test tiles - 10 of each clay -- and I tested all of my stable
>glazes on them to see how the fit was, which was best, which ones really suck.
>You can spot my goofed up glaze (HCSM -2) -- At least it was consistently
>crawling on all nine tiles.
>
>The other box I took and threw three pieces from each sample. These I will
>be using for a reduction sample firing.
>
>I'm learning the GlazeChem program slowly thanks to Holly in PA, but
>reworking a glaze from glossy to matte is out of my league at this point
>-- any help
>would be great.
>
>Jonathan in LA
>GQ meets a brick wall: brick wall 2, GQ - 0
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
Paul Lewing on fri 17 sep 04
on 9/16/04 7:53 PM, Imbolchottie@AOL.COM at Imbolchottie@AOL.COM wrote:
> My question about the 20x5 is how to make it into a matte. Has anyone tried?
I have, Jonathon. I have two suggestions for you, and both will keep the
materials in the same nice 5x20 proportions.
Substitute talc for the wollastonite. The MgO in the talc is a much less
active flux at that temperature than the CaO in wollastonite. This will
also lower the COE a bit, which you may or may not need.
Or, substitute frit 3124 for the 3134. They are very similar, except that
3124 has alumina and 3134 does not. This substitution will also lower the
COE, but a lower COE is almost never a problem at midrange temperatures.
Too high a COE is far more common.
One or both of these substitutions will probably make it matte. If not,
you're probably going to have to deviate from the 5x20 proportions by adding
more EPK or lowering one of the fluxes.
Good luck,
Paul Lewing, Seattle
Ivor and Olive Lewis on sat 18 sep 04
Dear Paul Lewing,
Given <Has anyone tried>>.........
Your proposition << Substitute talc for the wollastonite. >> seems a
good suggestion.
But the principle you are invoking may destabilise the glaze since you
are proposing to reduce the degree of melting and lower the solvent
properties of the vitreous solution at the maturity temperature. This
allows undissolved materials to cause surface texture, matness, on
cooling.
Perhaps a better ploy would be to cool a well matured melt at a slower
rate. Allow
Wollastonite or Anorthite to crystallise from the melt, or even
Enstatite or Cordierite to form if Magnesium Silicate is substituted
to some degree or other.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
----- Original Message -----
From: "Paul Lewing"
To:
Sent: Saturday, 18 September 2004 7:04
Subject: Re: little left 'ot' re Glaze Question
> on 9/16/04 7:53 PM, Imbolchottie@AOL.COM at Imbolchottie@AOL.COM
wrote:
>
> > ?
>
> I have, Jonathon. I have two suggestions for you, and both will
keep the
> materials in the same nice 5x20 proportions.
> Substitute talc for the wollastonite. The MgO in the talc is a much
less
> active flux at that temperature than the CaO in wollastonite. This
will
> also lower the COE a bit, which you may or may not need.
> Or, substitute frit 3124 for the 3134. They are very similar,
except that
> 3124 has alumina and 3134 does not. This substitution will also
lower the
> COE, but a lower COE is almost never a problem at midrange
temperatures.
> Too high a COE is far more common.
> One or both of these substitutions will probably make it matte. If
not,
> you're probably going to have to deviate from the 5x20 proportions
by adding
> more EPK or lowering one of the fluxes.
> Good luck,
> Paul Lewing, Seattle
>
>
______________________________________________________________________
________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your
subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Ron Roy on sun 19 sep 04
Hi Jonathan,
The first decision you need to make is what kind of matte glaze you want to
make. There are several and the answer depends at least partially on how
you would want to use the glaze.
If you decide you want to use it as a liner - and have it stable - a
calcium matte would probably be the best choice.
The clay mattes (keep SiO2/Al2O3 ratio below 5) tend to not be stable
because they wind up short of silica.
Over supply of MgO, SrO and BaO will give mattes as well but they will
probably not be stable - and you should consider the toxicity associated
with BaO.
Boron works against devitrification by the way - it never re re
crystallizes - so having too much can slow the recrystallization down a
lot.
You can make just about any glaze matte if you step outside the limits far
enough.
Remember also that slow cooling is a great help - cool em slow enough and
just about anything will have the time to form crystals.
There are a couple of CaO mattes in our book - leave out the colourants and
start adding zircopax - or any of the zirconium silicates - about 10% will
give you a white for instance.
Let me know if you need more on this.
RR
>I'm learning the GlazeChem program slowly thanks to Holly in PA, but
>reworking a glaze from glossy to matte is out of my league at this point
>-- any help
>would be great.
>
>Jonathan in LA
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on mon 20 sep 04
Frit 3124 has close to half the Boron in it so you would need a lot more to
get the same melting - there are other frits that would be a better sub
than 3124 depending on what is needed.
RR
>They are very similar, except that
>3124 has alumina and 3134 does not. This substitution will also lower the
>COE, but a lower COE is almost never a problem at midrange temperatures.
>Too high a COE is far more common.
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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