Ned Ludd on sun 8 dec 02
>A couple of my regular glazes tend to settle out to a hard cake at the
>bottom of the bucket. I've tried a number of methods to break it up and
>mix it in.
> My latest and most successful tool to date is my regular pear shaped
>dolan trim tool. It really cuts into the hard pan and gets it loose.
>
>John Jensen, Mudbug Pottery
>mudbug@toadhouse.com, www.toadhouse.com
About the hard cake at bottom: you might want to try adding muriatic
acid: gradually, in modest increments. It would save your elbow
grease for other jobs. Breaking up a lot of wet hard cake is no fun:
we potters wear out fast enough as it is... :-/
Be aware that the liquid wants careful handling, mind. It's one of
those things that aren't exactly idiot proof .. .
best,
Ned
John Jensen on sun 8 dec 02
A couple of my regular glazes tend to settle out to a hard cake at the
bottom of the bucket. I've tried a number of methods to break it up and
mix it in.
My latest and most successful tool to date is my regular pear shaped
dolan trim tool. It really cuts into the hard pan and gets it loose.
John Jensen, Mudbug Pottery
mudbug@toadhouse.com, www.toadhouse.com
Richard Mahaffey on mon 9 dec 02
John,
I have had success by adding bentonite to wet glaze by putting water in
a blender turning it on and SLOWLY adding bentonite while it runs. The
resultant mixture can then be added to the glaze batch.
Rick Mahaffey
Tacoma Community College
Tacoma, Washington, USA
Ababi on mon 9 dec 02
There are two ways (That I know)
Adding magnesium sulfate to the slurry, I don't remember how much See in Vince's
book "Clay".
The second which is the better: reformulate the glaze have more kaolin or ball clay up
to 25% of the recipe.
If you don't have a glaze software you can e mail me the recipe and I will do my best.
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910/
http://www.milkywayceramics.com/cgallery/asharon.htm
David Beumee on mon 9 dec 02
12/8/02 9:10:35 PM, John Jensen wrote:
>A couple of my regular glazes tend to settle out to a hard cake at the
>bottom of the bucket. I've tried a number of methods to break it up and
>mix it in.
> My latest and most successful tool to date is my regular pear shaped
>dolan trim tool. It really cuts into the hard pan and gets it loose.
Dear John,
Here's a trick for you that has always served me well. Mix Epsom salts in a quart of warm water until the solution
becomes so saturated that unmelted crystals begin to appear. Keep this solution tightly covered. Now break up
your hard-panned glazes and add about two tablespoons of the solution for a full five gallon bucket of glaze, or
about 10,000 grams of mixed dry glaze. This should cure your troubles.
David Beumee
Earth Alchemy Pottery
Lafayette, CO
>
>John Jensen, Mudbug Pottery
>mudbug@toadhouse.com, www.toadhouse.com
>
>______________________________________________________________________________
>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 mon 9 dec 02
on 12/8/02 10:37 PM, Ned Ludd at nludd@SHOCKING.COM wrote:
>> A couple of my regular glazes tend to settle out to a hard cake at the
>> bottom of the bucket.
>> My latest and most successful tool to date is my regular pear shaped
>> dolan trim tool. It really cuts into the hard pan and gets it loose.
John, the trouble with that method is that it will settle again as soon as
you stop stirring it. It has been suggested to you to use Epsom salts or
muriatic acid to try to get this batch to suspend, and that a better
long-term fix is to adjust the recipe so that it has more clay in it.
But the best way to deal with this particular bucket of glaze is to let it
dry completely, bust it up to powder, strain it dry, add some bentonite
(maybe 2% of the dry weight) and add that back into new water. Wear a mask
when you do the powder thing.
Paul Lewing, Seattle
Cindi Anderson on mon 9 dec 02
Get yourself a stick blender for about $15 (the kind you use in the
kitchen.) Works awesome for that.
Cindi
----- Original Message -----
From: "John Jensen"
> A couple of my regular glazes tend to settle out to a hard cake at the
> bottom of the bucket. I've tried a number of methods to break it up and
> mix it in.
> My latest and most successful tool to date is my regular pear shaped
> dolan trim tool. It really cuts into the hard pan and gets it loose.
iandol on tue 10 dec 02
Dear Ned Ludd,=20
I take it you are recommending the Hydrochloric acid treatment for those =
glazes which are devoid of Carbonate components. If not, they will =
become soluble salts and leach into the bisque clay.
I would also test with an indicator before plunging a hand in to stir =
after this treatment as well.
Best regards,
Ivor Lewis. Redhill, South Australia
Les Crimp on tue 10 dec 02
Vince -
What is your take on the use of Epsom Salts instead of bentonite to keep
glazes from compacting?
Les Crimp on the rainy, windy Great Northwest Rainforest (Vancouver Island)
lcrimp@shaw.ca
www.arrowsmithpottersguild.bc.ca
Rare - Earth - Design on tue 10 dec 02
>
> John, the trouble with that method is that it will settle again as soon as
> you stop stirring it. It has been suggested to you to use Epsom salts or
> muriatic acid to try to get this batch to suspend, and that a better
> long-term fix is to adjust the recipe so that it has more clay in it.
>
> But the best way to deal with this particular bucket of glaze is to let it
> dry completely, bust it up to powder, strain it dry, add some bentonite
> (maybe 2% of the dry weight) and add that back into new water. Wear a
mask
> when you do the powder thing.
>
> Paul Lewing, Seattle
I seem to remember from your original post that you already had 5% bentonite
in this recipe. Be very careful adding this stuff, when it solidifies you
would need
a hammer to break it up, that is if you could get it off the bottom of the
container.
I suspect that it is the bentonite which is the cause of the original
hardening,
and it is not every glaze to which this should be added.
Try mixing a smaller batch without bentonite and see does it settle out
hard.
Regards,
Bob Hollis
Mary White on tue 10 dec 02
I'm glad somebody brought this up. I am no glaze expert but I've had
some experience making wine. Bentonite is added near the end of the
process because it settles the suspended material in the liquid. It
forms a grey sludge in the bottom of the carboy and you then siphon
off the clarified wine.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Mary
on the wet west coast of British Columbia
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>I seem to remember from your original post that you already had 5% bentonite
>in this recipe. Be very careful adding this stuff, when it solidifies you
>would need
>a hammer to break it up, that is if you could get it off the bottom of the
>container.
>I suspect that it is the bentonite which is the cause of the original
>hardening,
>and it is not every glaze to which this should be added.
>Try mixing a smaller batch without bentonite and see does it settle out
>hard.
>
>Regards,
>Bob Hollis
>
>______________________________________________________________________________
>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.
--
vince pitelka on tue 10 dec 02
> I seem to remember from your original post that you already had 5%
bentonite
> in this recipe. Be very careful adding this stuff, when it solidifies you
> would need a hammer to break it up, that is if you could get it off the
bottom of
> the container. I suspect that it is the bentonite which is the cause of
the original
> hardening, and it is not every glaze to which this should be added. Try
mixing a
> smaller batch without bentonite and see does it settle out hard.
Whoa! On the contrary! The problem of glaze compaction at the bottom of
the bucket is usually caused by the non-plastic ingredients. The clays make
the glaze more creamy and help keep it in suspension. Adding a little
bentonite (5% is too much - 1% to 3% is usually fine) helps to make a
creamier glaze mixture which stays in suspension, and bentonite will never
make a glaze settle harder in the bottom of the bucket.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://iweb.tntech.edu/wpitelka/
Autumn Downey on wed 11 dec 02
Thanks for your reply, Vince,
You are right, there was only one glaze that I can think of that had a problem and it did have adequate clay already. It's fine without the bentonite.
Would you say that dolomite is a difficult ingredient? We never used it much until recently and I've noticed some settling in those glazes.
This is interesting too, about the water: Wonder why.
>Sometimes, even a well balanced glaze (adequate clay content) mixed too thin
>can settle badly when left for a few days. In that case, adding bentonite
>and/or Epsom salts might be a mistake, when it would be more effective to
>just decant off some of the water after the glaze settles overnight.
Autumn
Yellowknife Guild of Arts and Crafts website:
http://users.internorth.com/~downeya/index.html
vince pitelka on wed 11 dec 02
> Please read what I have written, I stand by my statement that too much
> bentonite will go rock-hard, 5% was already added to a glaze by the
> original author in his query, he then asked should he use a further 2% or
> so. Make up a test batch of one of your glazes and add 7% bentonite, you
will
> get a surprise.
Hey Bob, it seems to me that what you wrote was perfectly clear. When I get
back to the Craft Center in January I'd be glad to mix up a test batch, but
in the mean time I'd like you to provide some sort of explanation for what
you are claiming here. It makes no sense at all. Too much bentonite will
certainly have undesirable effects, but how in the world will it make a
glaze settle rock hard? It would have entirely the opposite effect.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://iweb.tntech.edu/wpitelka/
May Luk on wed 11 dec 02
What would happen at 5% addition, or + 5% addition?
T.I.A.
May
U.K.
on 12/11/02 4:00 am, vince pitelka at vpitelka@DTCCOM.NET wrote:
>> I seem to remember from your original post that you already had 5%
> bentonite
>> in this recipe. Be very careful adding this stuff, when it solidifies you
>> would need a hammer to break it up, that is if you could get it off the
> bottom of
>> the container. I suspect that it is the bentonite which is the cause of
> the original
>> hardening, and it is not every glaze to which this should be added. Try
> mixing a
>> smaller batch without bentonite and see does it settle out hard.
>
> Whoa! On the contrary! The problem of glaze compaction at the bottom of
> the bucket is usually caused by the non-plastic ingredients. The clays make
> the glaze more creamy and help keep it in suspension. Adding a little
> bentonite (5% is too much - 1% to 3% is usually fine) helps to make a
> creamier glaze mixture which stays in suspension, and bentonite will never
> make a glaze settle harder in the bottom of the bucket.
> Best wishes -
> - Vince
>
Autumn Downey on wed 11 dec 02
This is for Vince too, to confirm or not.
My take on bentonite or other clays was that they worked with Epsoms salts. That is they provided the particles that could loosely move around in the glaze and the Epsom's salts changed the charge in the glaze water so they would.
I've not been happy with bentonite in some glazes - seems to slow drying and causes cracking.
Autumn Downey
Yellowknife, NWT
At 07:56 PM 2002-12-10 -0800, you wrote:
>Vince -
>
>What is your take on the use of Epsom Salts instead of bentonite to keep
>glazes from compacting?
>
>Les Crimp on the rainy, windy Great Northwest Rainforest (Vancouver Island)
>lcrimp@shaw.ca
>www.arrowsmithpottersguild.bc.ca
>
>______________________________________________________________________________
>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.
>
>
Yellowknife Guild of Arts and Crafts website:
http://users.internorth.com/~downeya/index.html
vince pitelka on wed 11 dec 02
> What would happen at 5% addition, or + 5% addition?
May -
This is probably explained by a previous post I sent, but bentonite is the
finest of all clays, and with such fine particle size, it introduces very
high shrinkage. In excess of 3% bentonite you risk having problems with
excessive cracking of the glaze surface during drying. This will depend on
the proportion of non-plastics, and in some glazes you might get away with
4% or 5%. In general, 1% to 3% is an appropriate amount of bentonite to add
to a glaze that settles badly.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://iweb.tntech.edu/wpitelka/
vince pitelka on wed 11 dec 02
> My take on bentonite or other clays was that they worked with Epsoms
salts.
> That is they provided the particles that could loosely move around in the
glaze
> and the Epsom's salts changed the charge in the glaze water so they would.
I've
> not been happy with bentonite in some glazes - seems to slow drying and
> causes cracking.
Autumn -
The Epsom salts are going to have the greatest effect on the smallest
particles, so yes, they will act up on the clay. But the point is that if
you have adequate clay in a glaze recipe, you rarely need to add bentonite
or Epsom salts. It is only in the worst cases that you ever need to add
both.
Some people make the mistake of estimating the amount of bentonite to add to
a troublesome glaze, or else they calculate properly but just add too much.
Usually, 1% is enough, but you can add as much as 3% before you start having
trouble with cracking. And yes, the glaze coating will dry more slowly, for
the same reason that bentonite works so great for sealing agricultural
holding ponds. The super-fine bentonite particles seal the pores in the
soil, or in this case, the bisque-fired clay, and so it takes much longer
for the water to be absorbed into the clay. But I have never seen this be a
problem, so if you are having trouble with the glaze cracking AND with slow
drying, it sounds like your glaze might contain too much bentonite. Those
are probably the glazes that already had significant clay content and didn't
really need the bentonite.
Sometimes, even a well balanced glaze (adequate clay content) mixed too thin
can settle badly when left for a few days. In that case, adding bentonite
and/or Epsom salts might be a mistake, when it would be more effective to
just decant off some of the water after the glaze settles overnight.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://iweb.tntech.edu/wpitelka/
Rare - Earth - Design on wed 11 dec 02
Vince,
Please read what I have written, I stand by my statement that too much
bentonite will go rock-hard, 5% was already added to a glaze by the
original author in his query, he then asked should he use a further 2% or
so.
Make up a test batch of one of your glazes and add 7% bentonite, you will
get a surprise.
Regards,
Bob Hollis
> > I seem to remember from your original post that you already had 5%
> bentonite
> > in this recipe. Be very careful adding this stuff, when it solidifies
you
> > would need a hammer to break it up, that is if you could get it off the
> bottom of
> > the container. I suspect that it is the bentonite which is the cause of
> the original
> > hardening, and it is not every glaze to which this should be added. Try
> mixing a
> > smaller batch without bentonite and see does it settle out hard.
>
> Whoa! On the contrary! The problem of glaze compaction at the bottom of
> the bucket is usually caused by the non-plastic ingredients. The clays
make
> the glaze more creamy and help keep it in suspension. Adding a little
> bentonite (5% is too much - 1% to 3% is usually fine) helps to make a
> creamier glaze mixture which stays in suspension, and bentonite will never
> make a glaze settle harder in the bottom of the bucket.
> Best wishes -
> - Vince
Rare - Earth - Design on wed 11 dec 02
Further to my reply to Vince, Long many years ago we used bentonite
on the oil/gas exploration rigs to fill the drill holes and builders, power
company and telecom engineers in this very wet part of the world
throw loads of it into very wet holes as it goes solid and allows them
to carry on with their work.
Please do come back with the reply that they use large amounts, I know
they do, but I still say there are some glazes to which bentonite should
never be added. Glaze materials are cheap so it would be a simple matter
to make a sample batch and add bentonite, if it is still in suspension and
there is no settling out after a few days then go ahead and make a larger
batch.
Regards,
Bob Hollis
> What would happen at 5% addition, or + 5% addition?
>
> T.I.A.
> May
> U.K.
>
> on 12/11/02 4:00 am, vince pitelka at vpitelka@DTCCOM.NET wrote:
>
> >> I seem to remember from your original post that you already had 5%
> > bentonite
> >> in this recipe. Be very careful adding this stuff, when it solidifies
you
> >> would need a hammer to break it up, that is if you could get it off the
> > bottom of
> >> the container. I suspect that it is the bentonite which is the cause of
> > the original
> >> hardening, and it is not every glaze to which this should be added. Try
> > mixing a
> >> smaller batch without bentonite and see does it settle out hard.
> >
> > Whoa! On the contrary! The problem of glaze compaction at the bottom
of
> > the bucket is usually caused by the non-plastic ingredients. The clays
make
> > the glaze more creamy and help keep it in suspension. Adding a little
> > bentonite (5% is too much - 1% to 3% is usually fine) helps to make a
> > creamier glaze mixture which stays in suspension, and bentonite will
never
> > make a glaze settle harder in the bottom of the bucket.
> > Best wishes -
> > - Vince
>
Rare - Earth - Design on thu 12 dec 02
Too much bentonite will
> certainly have undesirable effects, but how in the world will it make a
> glaze settle rock hard? It would have entirely the opposite effect.
> Best wishes -
> - Vince
> Ah Vince, that is the part I don't understand, but I know it happens.
Perhaps it has got to do with adding bentonite to an already mixed batch.
It happened to me when I used to employ people and one person who
had a little knowledge decided all the glazes needed bentonite, she had
first added water as she thought them too thick. Two of my glazes then
formed a cake on the bottom about 2 inches thick, I'm talking here 30
gallons each, imperial, and in the end I managed to get it off the bottom
and dumped it, through testing and messing I got the glazes back to
acceptable results. I dumped the bentonite and, just in case, the Epsom
Salts also. Haven't had employees for nigh on 4 years but to this day I
do not have these ingredients in my studio. Do things right and you don't
need them, spend a couple of minutes each morning stirring glages which
are prone to settling.
Another thing which I do notice is that certain glazes which are mixed for
the first time using a metal plaster mixer on a high speed drill will
thicken
up just like whipping cream and you have to add gallons of water and stir
gently two or three times a day for about 3 days and then it suddenly
settles
down and you can take out all the water again, Why? I don't know and it does
not happen to every glaze.
The thing is I am not at all interested in how or why these things happen
as long as I can work around them and get on with making a living from my
pots, not quite true, my wife is also a potter and we do make our living
only from our pottery.
Regards,
Bob Hollis
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