Donna Kat on wed 31 oct 07
Rudy's Black,
Feldspar - Custer ,4920.00,
Kaolin - EPK ,1990.00,
Whiting ,1790.00,
Zinc Oxide ,800.00,
Flint ,500.00,
Cobalt Oxide ,130,
Iron Oxide - Red ,670,
This is a studio glaze that someone probably mixed up wrong - It is
consistently a reliable glaze that gives a smooth matt finish (too little
silica). It is now crawling in a pretty uniform way. Whoever mixed it up
also used the wrong cobalt (carbonate). I added 1/4 the amount of Cobalt
Oxide to bring it back to black from brown, resieved it repeatedly and it
is now the right color but still does not have a smooth surface (just a
tiny suggestion of crawling.
IMO the glaze should not be used in the studio but given that it is and
that there is 10000 grams of material here that I hate to see wasted - is
there a way to save this glaze? The people who started mixing up the
glazes were measuring out in under 500gm batches - so for Whiting they
would measure 500, 500, 500 and 290 grams of material (don't ask why). My
guess is that in one of the materials they either counted one measure
twice or added an additional measure (so with whiting as an example ended
up with either 1290 grams or 2290 grams rather than the 1790).
The searches I have done on crawling don't really help. Any suggestions
would be appreciated.
Donna
P.S. I hate to clutter the room with my messages so I don't say thank you
to all the helpful messages I get here (even though I really want to). I
just want to say how much I appreciate the advice and effort put in here
and to say Thank You!!!!
Terrance Lazaroff on thu 1 nov 07
Donna;
It is my opinion and I am not an expert at glaze manipulation, so you may
receive better info from some of the experts on the list but I believe your
ambition to try and save this glaze may cost you more that the batch is
worth. This could take a tremendous amount of time and possibly a cost a
lot more money that the original glaze recipe is worth. The recipe that
you posted is the original; the mixture is the unknown. The only thing you
could do that would be close to solving your delema is to dry the glaze
batch, crush to a fine powder and treat the mixture as a glaze material in
a glaze quadriaxel. You might find a glaze that works then again you may
not.
Again that is just my feelings. I could be wrong.
Terrance
Be sure to visit my website at http://clayart.ca
Ron Roy on thu 1 nov 07
Hi Donna,
First of all the glaze (cone6?) is short of silica so it's not a good bet
as a liner glaze. Zinc has a reputaion of encouraging crawling - if I add
more zinc the situation gets worse - less silica - but I'm just guessing
about which material is wrong.
I really have no idea of how to guess what went wrong. I would suggest
making piles of each material and can count the piles before adding them to
the batch.
RR
>Rudy's Black,
>
>Feldspar - Custer ,4920.00,
>Kaolin - EPK ,1990.00,
>Whiting ,1790.00,
>Zinc Oxide ,800.00,
>Flint ,500.00,
>
>Cobalt Oxide ,130,
>Iron Oxide - Red ,670,
>
>This is a studio glaze that someone probably mixed up wrong - It is
>consistently a reliable glaze that gives a smooth matt finish (too little
>silica). It is now crawling in a pretty uniform way. Whoever mixed it up
>also used the wrong cobalt (carbonate). I added 1/4 the amount of Cobalt
>Oxide to bring it back to black from brown, resieved it repeatedly and it
>is now the right color but still does not have a smooth surface (just a
>tiny suggestion of crawling.
>
>
>IMO the glaze should not be used in the studio but given that it is and
>that there is 10000 grams of material here that I hate to see wasted - is
>there a way to save this glaze? The people who started mixing up the
>glazes were measuring out in under 500gm batches - so for Whiting they
>would measure 500, 500, 500 and 290 grams of material (don't ask why). My
>guess is that in one of the materials they either counted one measure
>twice or added an additional measure (so with whiting as an example ended
>up with either 1290 grams or 2290 grams rather than the 1790).
>
>The searches I have done on crawling don't really help. Any suggestions
>would be appreciated.
>
>Donna
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Edouard Bastarache Inc. on thu 1 nov 07
Hi Donna,
"Rudy's Black,
Feldspar - Custer ,4920.00,
Kaolin - EPK ,1990.00,
Whiting ,1790.00,
Zinc Oxide ,800.00,
Flint ,500.00,
Cobalt Oxide ,130,
Iron Oxide - Red ,670,"
Using GlazeChem and Val Cushung's limits, this
base should be good
for a C/5-6 satin or matt glaze
Gis la revido,
(A la revoyure)
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://perso.orange.fr/smart2000/livres.htm
http://www.pshcanada.com/Toxicology.htm
http://www.ceramique.com/librairie/
http://www.flickr.com/photos/30058682@N00/
http://myblogsmesblogs.blogspot.com/
Donna Kat on thu 1 nov 07
On Thu, 1 Nov 2007 03:14:08 -0500, Ron Roy wrote:
>Hi Donna,
>
>First of all the glaze (cone6?) is short of silica so it's not a good bet
>as a liner glaze. Zinc has a reputaion of encouraging crawling - if I add
>more zinc the situation gets worse - less silica - but I'm just guessing
>about which material is wrong.
>
>I really have no idea of how to guess what went wrong. I would suggest
>making piles of each material and can count the piles before adding them
to
>the batch.
>
>RR
>
I had two ideas -
1. add more silica in 500 gram batches up to 1500 grams (10000 grams of
glaze) which would be better for the glaze in general (this would also cut
down the percentage of the material that was causing the problem I thought.
2. dry out the glaze and bisque fire it to calcinate the Kaolin.
Are either of these a possible way to go or would the Bad Idea Bears be
thrilled? (any Avenue Q fans?)
When I make up the glazes I have all sorts of checks and double checks in
making sure I don't screw up (because I'm really, really good at getting
distracted). When I'm making up small batches I put the ingredients on
paper and write the ingredient and weight by each measure next to the
pile. I can't do that with 10000 gram batches when there is a large
amount of one ingredient so I make up a new glaze card and write each
ingredient and the amount measured and checked as it is added to the
bucket. This card then gets taped to the bucket until the test comes out
as OK.
Currently the studio is being run by someone who is - not thrilled with
making glazes shall we say. Add to that work study students who know
nothing of pottery let alone chemistry and who are being left on their own
to do what others don't want to do...
Donna
P.S. My task for today is to add to each bucket of my ingredients a
laminated label of what the ingredient is. Once again, thank you all for
your invaluable help (if I posted that to each message that was helpful to
me the room would be cluttered by my thank yous)!
John Hesselberth on thu 1 nov 07
On Nov 1, 2007, at 11:23 AM, Edouard Bastarache Inc. wrote:
> Using GlazeChem and Val Cushung's limits, this
> base should be good
> for a C/5-6 satin or matt glaze
Hi Edouard,
The limits that are published are all based on visual examination.
There has been no testing of those glazes for durability. So your use
of the word "good" has to be considered questionable if the potter is
interested in durable, functional glazes. For more information on
this subject see the article based on a literature search I did
several years ago at
http://www.frogpondpottery.com/glazestab.html
Published limit formulas are virtually useless for a functional
potter who wants her pots to hold up in use. They include glazes that
are very unstable (usually low silica mattes) and exclude glazes that
are very beautiful and durable mattes (high alkaline earth glazes
with plenty of alumina and silica).
I believe a better set of "limits" are found in the 4 rules that Ron
and I developed for Mastering Cone 6 Glazes". In brief they are 1)
enough silica 2) enough alumina 3) thoroughly melt and 4) don't
overload with colorants, particularly copper.
Regards,
John
John Hesselberth
www.masteringglazes.com
www.frogpondpottery.com
Edouard Bastarache Inc. on thu 1 nov 07
John,
by "good" I did not mean it is a good glaze for
whatever possible uses .
I just meant it suits Val Cushing's limits for a
satin
or matt glaze at C/6.
Gis la revido,
(A la revoyure)
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://perso.orange.fr/smart2000/livres.htm
http://www.pshcanada.com/Toxicology.htm
http://www.ceramique.com/librairie/
http://www.flickr.com/photos/30058682@N00/
http://myblogsmesblogs.blogspot.com/
----- Original Message -----
From: "John Hesselberth"
To:
Sent: Thursday, November 01, 2007 6:06 PM
Subject: Re: Help! Can this Glaze be saved?
> On Nov 1, 2007, at 11:23 AM, Edouard Bastarache
> Inc. wrote:
> Mime-Version: 1.0
> Content-Transfer-Encoding: 7bit
> Content-Type: text/plain; charset=US-ASCII;
> delsp=yes; format=flowed
>
>> Using GlazeChem and Val Cushung's limits, this
>> base should be good
>> for a C/5-6 satin or matt glaze
>
> Hi Edouard,
>
> The limits that are published are all based on
> visual examination.
> There has been no testing of those glazes for
> durability. So your use
> of the word "good" has to be considered
> questionable if the potter is
> interested in durable, functional glazes. For
> more information on
> this subject see the article based on a
> literature search I did
> several years ago at
>
> http://www.frogpondpottery.com/glazestab.html
>
> Published limit formulas are virtually useless
> for a functional
> potter who wants her pots to hold up in use.
> They include glazes that
> are very unstable (usually low silica mattes)
> and exclude glazes that
> are very beautiful and durable mattes (high
> alkaline earth glazes
> with plenty of alumina and silica).
>
> I believe a better set of "limits" are found in
> the 4 rules that Ron
> and I developed for Mastering Cone 6 Glazes". In
> brief they are 1)
> enough silica 2) enough alumina 3) thoroughly
> melt and 4) don't
> overload with colorants, particularly copper.
>
> Regards,
>
> John
>
>
>
> John Hesselberth
> www.masteringglazes.com
> www.frogpondpottery.com
>
> ______________________________________________________________________________
> Clayart members may send postings to:
> clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post
> messages, or change your
> subscription settings here:
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>
> Moderator of the list is Mel Jacobson who may be
> reached at melpots2@visi.com
>
>
>
> --
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>
Donna Kat on sun 4 nov 07
On Thu, 1 Nov 2007 03:14:08 -0500, Ron Roy wrote:
>Hi Donna,
>
>First of all the glaze (cone6?) is short of silica so it's not a good bet
>as a liner glaze. Zinc has a reputaion of encouraging crawling - if I add
>more zinc the situation gets worse - less silica - but I'm just guessing
>about which material is wrong.
>
I did not expect to find out what went wrong. What I wanted to know was
if I add more silica since the glaze is short on silica to begin with,
what will the possible results be.
I also was browsing through the MC6 site again (since I have no memory I
have to refresh frequently) and saw the version of Licorice where
calcinate Kaolin replaces the regular EPK and this version is then mixed
in equal parts with the original mix which is crawling. This must have
been what started the idea of drying out the glaze and firing it in a
bisque fire.... (that seems like less of a good idea now given how much
glaze there is and that I have no idea what it would do to the other
ingredients).
The glaze recipe does not seem to have too much zinc even if it was
accidently doubled. It does have far too little silica and a large amount
of Kaolin. So I'm now thinking of mixing up a second batch with the
calcinated Kaolin, more silica and mixing this with the faulty batch. I
just can't bring myself to throw away 10000 grams of a $40-50 glaze and if
I can do tests batches of 500ml (~334grms) with possible solutions it
doesn't seem like much time or effort to do so.
Donna
P.S. The glaze is actually kind of interesting as is but not acceptable
for a crafts studio.
Terrance Lazaroff on mon 5 nov 07
Donna;
I have to say it again. The glaze you have is not what the recipe says.
The best way to salvage it is to dry it out and do a series of test tiles.
That way you will know what to add and in what percentage in order to
salvage the glaze. Working wet could lead to a lot of time loss and a lot
of additional costs without success.
Terrance
Visit my website at http://clayart.ca
Ron Roy on tue 6 nov 07
Hi Donna,
I would recommend taking a cup of glaze and adding silica to it - 5, 10, 20
grams of silica - sieve it and fire it to see what happens.
If it's short of silica then it will probably become more shiny - if there
is already enough silica then it may not melt well.
If you think there is too much Alumina mix up the glaze without alumina and
combine that with different amounts of the mistake - like 25/75, 50/50
75/25 - but only small batches till you find out what works best.
RR
>I did not expect to find out what went wrong. What I wanted to know was
>if I add more silica since the glaze is short on silica to begin with,
>what will the possible results be.
>
>I also was browsing through the MC6 site again (since I have no memory I
>have to refresh frequently) and saw the version of Licorice where
>calcinate Kaolin replaces the regular EPK and this version is then mixed
>in equal parts with the original mix which is crawling. This must have
>been what started the idea of drying out the glaze and firing it in a
>bisque fire.... (that seems like less of a good idea now given how much
>glaze there is and that I have no idea what it would do to the other
>ingredients).
>
>The glaze recipe does not seem to have too much zinc even if it was
>accidently doubled. It does have far too little silica and a large amount
>of Kaolin. So I'm now thinking of mixing up a second batch with the
>calcinated Kaolin, more silica and mixing this with the faulty batch. I
>just can't bring myself to throw away 10000 grams of a $40-50 glaze and if
>I can do tests batches of 500ml (~334grms) with possible solutions it
>doesn't seem like much time or effort to do so.
>
>Donna
>
>P.S. The glaze is actually kind of interesting as is but not acceptable
>for a crafts studio.
>
>______________________________________________________________________________
>Clayart members may send postings to: clayart@lsv.ceramics.org
>
>You may look at the archives for the list, post messages, or change your
>subscription settings here: http://www.acers.org/cic/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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