Bryan Hannis on mon 6 apr 98
Hi
I have a glaze that is developing delayed crazing, I fire cone 10 reduction
propane fired. My clay body is Plainsman 435 and I also use 431/550 mix. The
glaze is semi matte, beige in color.
Custer Fel........372.0 gr.
EPK...............124.8 "
Whiting............48.0 "
dolomite..........156.0 "
Bent...............36.0 "
Zirco.............120.0 "
Rutile.............16.8 "
If anyone has any ideas that could help me I would be very appreciative.
TIA
Bryan Hannis
Carol & Herman Kremer on wed 6 may 98
------------------
I have a glaze that I think is wonderful - when it works. It is interesting=
-
mottled and glossy. The problem is that it isn't reliable. Sometimes it =
comes
out dull and matt - ugly=21
I fire to 05 or 06 in an electric kiln. The formula is:
gerstley borate 43.27=25
feldspar 10.82=25
flint 21.63=25
epk 3.47
lithium carbonate 10.00
I like it best in blue so add:
cobalt oxide 2=25
turquoise stain 5=25
What can I do with this glaze to make it reliable? I would appreciate any =
help
I can get.
Carol
S. Houde on wed 24 jun 98
I have a few glaze problems that I could use some advice on. Can anyone
help me out?
I have been using the following cone 6 glaze recipe for about 10 years
with good results. Pieces that I have used for many years are large and
I have not used the dishwasher on them. I recently glazed some
dinnerware in the cobalt blue version that I have been cleaning in the
dishwasher daily. The glaze on 1 piece seems to have changed. The
glaze seems to be getting lighter in some areas and also it seems that
the glaze has eroded leaving some areas raised (almost like clay looks
when painted with wax or shellac then wiping away the clay around the
protected area.). Is it possible for a glaze to change with
dishwashing? Why would this happen on one piece but not the others? If
so how can I prevent this? (short of not using the glazed work in the
dishwasher). Can I somehow alter the recipe so it can withstand the
dishwasher detergents? Is it safe to use for foods? It should be noted
that I have been using the chrome color phase of this glaze in the
dishwasher for 8 years with out any noticable changes.
Cobalt Blue Emerald Green
Milky Gloss Glaze Cone 5-6 Milky Gloss Glaze Cone 5-6
Instead of cobalt oxide@5.0%and Ultrox at 5.0% use:
Gerstley Borate 49.0%
Chrome oxide 2.0%
EPK 19.0% cobalt oxide 1.5%
Flint 32.0%
_____
100.0%
soda ash 0.2%
Cobalt oxide 5.0%
Ultrox 5.0%
This recipe came from Ceramics Monthly, October 1986.
My second question :
I use the following cone 4-10 clear glaze. Sometimes the glaze moves
causing the underglaze oxide to run or the glazes sprayed on top to run
or crawl off the piece. The thickness of the glaze seems to make a
difference. Sprayed glazes don't run as much or as often as when I dip
the glaze. Can I alter the glaze so that its less prone to moving?
I fire to cone 6 in oxidation.
Cone 4-10 Clear Glaze
EPK 30.0%
Gerstley Borate 20.0%
Whiting 20.0%
Flint 30.0%
Thank you for your advice in advance. Sincerely,
Sarah Houde
Craig Martell on thu 25 jun 98
>----------------------------Original message----------------------------
>I have a few glaze problems that I could use some advice on. Can anyone
>help me out?
If you look at the first glaze in the molecular state, there is about 3
times the usual limit of boron. Boron will add a less durable glass to the
glaze and render it more soluble. The silica is within limits for the cone
3-7 range and the alumina is ok too. The alumina level will vary if the
Gerstley Borate you are using does not conform to the analysis. This stuff
is incredibly variable and I would say that it's not a good idea to use a
glaze with only GB as the main flux for functional ware. The logic here is
that if the ONE ingredient used as flux is highly variable, there will more
than likely be problems. I would find another glaze!
There are some very good glazes in your temp range with a better selection
of fluxing agents. I always like to see some sort of feldspathic material
in functional glazes and feldspar based glazes will work very well for
functional pots. I think it's always a good idea to have at least 2
reliable fluxing agents in a glaze. Three or more is even better if you
consider that radical deviation in the glaze is less likely. Of course, it
all depends on the kind of glaze and color response that you want too.
regards, Craig Martell-Oregon
James Norton on tue 12 jan 99
I have trouble with copper carbonate volatilizing badly with my cone 6
ox. glazes. I have heard somewhere that adding tin to the recipe helps
prevent this. Can anyone affirm this? If so, what percent is
advisable?
Earl Brunner on wed 13 jan 99
One of the GREAT ONES may correct me on this, but I'm not sure that it
is necessarily the copper that is the problem. I am traditionally a Cone 10
redux potter but because of where I teach have done quite a bit of 05-06
Oxidation over the last three years. I think that the chemicals used at
this temp.
particularily the fluxes cause ALL the glazes we use to volotalize, I'm
ALWAYS getting little vapor rings of color on the shelves around the pots
at cone 05-06 and copper doesn't seem to have much to do with it.
Earl Brunner
James Norton wrote:
> ----------------------------Original message----------------------------
> I have trouble with copper carbonate volatilizing badly with my cone 6
> ox. glazes. I have heard somewhere that adding tin to the recipe helps
> prevent this. Can anyone affirm this? If so, what percent is
> advisable?
Tom Buck on thu 14 jan 99
James N:
In an oxidation firing Copper carb switches to CuO (black oxide)
soon after 200 oC is reached. The black oxide undergoes change at 1026 oC,
its crystalline sructure breaks down, and at 1325 oC the CuO melts. Now C6
is approx. 1230 oC, not too far from CuO's melting point, so the copper
oxide black will have a significant vapour pressure, ie, a portion of the
CuO will go to vapour. But the loss would not be as much as you seem to
suggest, likely under 10%. But loss would be increased by a long soak at
C6/5.
Tin oxide is not reccomended for use with a copper oxide colourant
in an oxidation firing; it would largely be a filler/opacifier and dilute
the colour response.
However, in a reduction firing, when a copper red glaze is
desired, then tin oxide is added to serve as a catalyst of the
conversion of CuO (black) to Cu2O (red) and Cu metal. The usual amounts
are up to 1% Copper Carb and 1% tin oxide.
Til later. Tom.
Tom Buck ) tel: 905-389-2339
& snailmail: 373 East 43rd St. Hamilton ON L8T 3E1 Canada
(westend Lake Ontario, province of Ontario, Canada).
On Tue, 12 Jan 1999, James Norton wrote:
> ----------------------------Original message----------------------------
> I have trouble with copper carbonate volatilizing badly with my cone 6
> ox. glazes. I have heard somewhere that adding tin to the recipe helps
> prevent this. Can anyone affirm this? If so, what percent is
> advisable?
>
Thomas J. Herr on thu 7 oct 99
------------------
I am having a problem with one of my glaze recipes and would appreciate some
advice. After sitting unused between glazing sessions, this particular =
glaze
settles to the bottom as a thick, almost dry cake. I must drain all the =
liquid
and then chip away the settled ingredients which was about 3 inches thick =
and
add it back to the liquid. After the last time I used it, I added a =
commercial
glaze stabilizer. Although it has stabilized the glaze so that it no longer
settles, it is now so thick that it not only takes a longer time to dry when=
I
dip my pieces for glazing, but the fired glaze no longer looks as nice as it=
did
before I added the stabilizer. Question =231: Can I salvage the remainder =
of my
glaze? Question =232: Is there a substitution I can make in future batches=
to
avoid this problem?
The recipe is as follows:
Soda feldspar 5500g
Whiting 2200g
Bentonite 200g
Flint 1400g
Tin oxide 300g
Copper oxide 365g
Any help or suggestions would be greatly appreciated=21
Patty Herr, Potter
therr=40earthlink.net
Paul Lewing on thu 7 oct 99
Hi, Patti.
You don't say what cone this glaze fires to, so it's kind of hard to
offer specific quantities here, but I'm not a bit surprised that it
settles so hard. Other than the bentonite, which was probably added in
the first place as an attempt to stop the settling, there is no clay in
there. Clay is usually what keeps a glaze suspended in water.
Virtually all the other glaze materials are essentially powdered rocks,
so it's not surprising that they settle in water.
I'd start fixing this glaze be adding about 3% increments of kaolin to
it. You'll probably find that an addition of about 6% kaolin will keep
it suspended without altering it too much. And I'd leave the bentonite
in, too, which means that you have to mix all the ingredients dry before
you add them to water- otherwise the bentonite will not mix in and do
its job.
Also you're not going to be able to do this test as a traditional line
blend. If you were only testing the fired characteristics, you could
make a batch with 3% kaolin added, test that, then add 3 more % and test
that, and so on. But since you're interested in which increment amount
will keep it suspended with the least amount of clay (thereby changing
the glaze the least) you need to mix a separate batch with each
incremental amount and keep them all around to try to stir up later.
Hapy testing,
Paul Lewing, Seattle, where summer was way too short, but Indian Summer
was great. Looks like it's ending now, though.
Martin Howard on fri 8 oct 99
Patty Herr might follow my example and invest in cats :-)
My basic glaze has 20% cat litter, which is montmorrillonite or
bentonite. Increase the bentonite.
The only glazes in my pottery which settle down are those I bought to
match the clay. They all craze.
None of my glazes based on 20/20/60 cat litter/granite dust/standard
borax frit craze at all and are a real joy to work with.
Having a problem getting a real black though.
Martin Howard
Webbs Cottage Pottery and Press
Woolpits Road, Great Saling
BRAINTREE
Essex CM7 5DZ
01371 850 423
araneajo@gn.apc.org
DONALD G. GOLDSOBEL on sat 9 oct 99
To what temp do you fire these glazes?
At 11:09 AM 10/08/1999 EDT, you wrote:
>----------------------------Original message----------------------------
>Patty Herr might follow my example and invest in cats :-)
>My basic glaze has 20% cat litter, which is montmorrillonite or
>bentonite. Increase the bentonite.
>The only glazes in my pottery which settle down are those I bought to
>match the clay. They all craze.
>None of my glazes based on 20/20/60 cat litter/granite dust/standard
>borax frit craze at all and are a real joy to work with.
>
>Having a problem getting a real black though.
>
>Martin Howard
>Webbs Cottage Pottery and Press
>Woolpits Road, Great Saling
>BRAINTREE
>Essex CM7 5DZ
>01371 850 423
>araneajo@gn.apc.org
>
Ron Roy on sat 9 oct 99
Hi Patty,
I'm guessing this is a cone 10 glaze. I have used frit 3134 to get some raw
clay into the recipe - it will stay suspensed much better. I'm fairly sure
this will look very close to your original and has the added advantage of
having a lower expansion which should help with the crazing.
RR's revision
-----------------
F4 SPAR............. 46.00
F3134............... 10.00
WHITING............. 19.00
OM-4................ 10.00
SILICA.............. 15.00
BENTONITE........... 2.00
TIN................. 3.00
copr ox............. 3.50
----------
Total......................108.50
If it works you can then mix up a big batch and add some of the older
recipe to it and use it up over several batches.
RR
>----------------------------Original message----------------------------
>I am having a problem with one of my glaze recipes and would appreciate some
>advice. After sitting unused between glazing sessions, this particular glaze
>settles to the bottom as a thick, almost dry cake. I must drain all the liquid
>and then chip away the settled ingredients which was about 3 inches thick and
>add it back to the liquid. After the last time I used it, I added a commercial
>glaze stabilizer. Although it has stabilized the glaze so that it no longer
>settles, it is now so thick that it not only takes a longer time to dry when I
>dip my pieces for glazing, but the fired glaze no longer looks as nice as
>it did
>before I added the stabilizer. Question #1: Can I salvage the remainder of my
>glaze? Question #2: Is there a substitution I can make in future batches to
>avoid this problem?
>
>The recipe is as follows:
>
>Soda feldspar 5500g
>Whiting 2200g
>Bentonite 200g
>Flint 1400g
>Tin oxide 300g
>Copper oxide 365g
>
>Any help or suggestions would be greatly appreciated!
>
>Patty Herr, Potter
>therr@earthlink.net
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
Martin Howard on mon 11 oct 99
DONALD G. GOLDSOBEL [pots@pacificnet.net] asks
To what temp do you fire these glazes?
>Patty Herr might follow my example and invest in cats :-)
>My basic glaze has 20% cat litter, which is montmorrillonite or
>bentonite. Increase the bentonite.
>The only glazes in my pottery which settle down are those I bought to
>match the clay. They all craze.
>None of my glazes based on 20/20/60 cat litter/granite dust/standard
>borax frit craze at all and are a real joy to work with.
>
>Having a problem getting a real black though.
Answer
All at cones 02 through to 1. The kiln is set at 1100 degrees C. The
bottom gets to that and the top about 1140.
Martin Howard
>Webbs Cottage Pottery and Press
>Woolpits Road, Great Saling
>BRAINTREE
>Essex CM7 5DZ
>01371 850 423
>araneajo@gn.apc.org
>
Don Lyons on wed 2 feb 00
The Lexington Arts and Crafts Ceramic Guild is having a problem with
our celadon glaze, which has always been fine in the past. It has
settled into an extremely hard mass soon after making it. Thinking that
a mistake was made in measurement, a second batch was carefully made but
the same settling occured. It seems impossible to bring it to the normal
consistency, though a very small amount was obtained and tested. The
test, done in a test kiln, was normal. We fear that one of our
chemicals was either mislabled by the supplier.Could one of the
ingredients have a larger than normal mesh size and be responsible for
the settling? The formula follows:
Custer spar: 41.5, Whiting: 8, Strontium Carb: 9.9, EPK: 7.8, Flint:
32.3, Bentonite: 2, Red iron: 2.
Any ideas out there?? We've tried the usual. Our oribe glaze has all the
ingedients as the celadon plus talc, bone ash and black copper oxide
instead of red iron, and it seems normal.
Peter Jones on thu 3 feb 00
Don: The first place I'd look for the settling problem culprit is your
flint (silica). It is usually available in two different mesh sizes: 325
and 200. They are eseentially indistinguishable to the naked eye, yet the
200 mesh would settle out much faster in a glaze. 200 mesh is generally
reserved for clay bodies while the 325 is intended for glazes.
The flint most potters use is from the US Silica Co. Unfortunately, you
need the code on the bag to determine which is which. The code numbers
don't match the mesh size. The code numbers are either 52 or 75. The 52
batch is 325 mesh, the 75 is the 200 mesh. It is highly likely that someone
at your clay supply company either didn't know the difference themselves or
just substituted the 200 mesh if it was not specified which one you wanted.
One thing you might try as a stopgap measure with the glaze you have already
mixed up is to add about 1% epsom salts (of the batch weight) to your glaze.
The salts help to keep your glaze in suspension. It may not work as well
with all that heavy flint in there, but it is worth a try before dumping the
entire batch.
Your Oribe glaze might be working better because of the bone ash in it. I
use only one glaze with bone ash (O'Hata Red) and it is so plastic that it
nearly flakes off the pot, a real pain in the neck. For some reason,
unbeknownst to me, it seems to keep things in suspension much better.
Perhaps someone knows the reason why it acts that way.
Hope that helps.
Peter Jones
----------
>From: Don Lyons
>To: CLAYART@LSV.UKY.EDU
>Subject: glaze problem
>Date: Wed, Feb 2, 2000, 4:58 PM
>
>----------------------------Original message----------------------------
>The Lexington Arts and Crafts Ceramic Guild is having a problem with
>our celadon glaze, which has always been fine in the past. It has
>settled into an extremely hard mass soon after making it. Thinking that
>a mistake was made in measurement, a second batch was carefully made but
>the same settling occured. It seems impossible to bring it to the normal
>consistency, though a very small amount was obtained and tested. The
>test, done in a test kiln, was normal. We fear that one of our
>chemicals was either mislabled by the supplier.Could one of the
>ingredients have a larger than normal mesh size and be responsible for
>the settling? The formula follows:
>Custer spar: 41.5, Whiting: 8, Strontium Carb: 9.9, EPK: 7.8, Flint:
>32.3, Bentonite: 2, Red iron: 2.
>Any ideas out there?? We've tried the usual. Our oribe glaze has all the
>ingedients as the celadon plus talc, bone ash and black copper oxide
>instead of red iron, and it seems normal.
>
>
Lois Atherton on mon 20 nov 00
Hi Connie,
No, I haven't had anyone reply to my question, so I'll ask again.
This is a great blue celadon, with the exception that from time to time I get
tiny bits of crawling on the rims of mugs, bowls, etc.
Pete's Blue Celadon =5E 10 Red. (from Sam Clarkson)
Custer (Potash) Feldspar 25.0
Whiting 20.0
Grolleg Kaolin 20.0
Flint 35.0
Add :
Tin Oxide 1.0
Barium Carbonate 2.0
Barnard Clay 3.0
I'm using a domestic porcelain. The glaze fires well from cone 9 to a pretty
hard 10.
I'm very careful about dust on the rims. Can't figure out why it happens...a
bit like Russian Roulette.
Anybody have any ideas?
Thanks!
Lois
Denis Caraty on mon 20 nov 00
I suppose the temperature is higher on the rims (due to the surface effect).
Denis Caraty
Societe : Faienceries de Gien
78, place de la victoire, 45500 Gien, FRANCE
Fax : (33) 2 38 67 92 36
dcaraty@gien.com
http://www.gien.com
-----Message d'origine-----
De : Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]De la
part de Lois Atherton
Envoye : lundi 20 novembre 2000 15:29
A : CLAYART@LSV.CERAMICS.ORG
Objet : Glaze Problem
Hi Connie,
No, I haven't had anyone reply to my question, so I'll ask again.
This is a great blue celadon, with the exception that from time to time I
get
tiny bits of crawling on the rims of mugs, bowls, etc.
Pete's Blue Celadon =5E 10 Red. (from Sam Clarkson)
Custer (Potash) Feldspar 25.0
Whiting 20.0
Grolleg Kaolin 20.0
Flint 35.0
Add :
Tin Oxide 1.0
Barium Carbonate 2.0
Barnard Clay 3.0
I'm using a domestic porcelain. The glaze fires well from cone 9 to a
pretty
hard 10.
I'm very careful about dust on the rims. Can't figure out why it
happens...a
bit like Russian Roulette.
Anybody have any ideas?
Thanks!
Lois
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Chris Schafale on mon 20 nov 00
Based on the amount of clay in the recipe, I suspect that the raw
glaze coat may be cracking and lifting up on the rims during the
early stages of firing. I have had those little (and some bigger)
crawls with similar glazes. You might try calcining some of the
clay content so that you have no more than 15% raw clay in the
recipe. Works for me.
Chris
> Hi Connie,
> No, I haven't had anyone reply to my question, so I'll ask again.
> This is a great blue celadon, with the exception that from time to time I get
> tiny bits of crawling on the rims of mugs, bowls, etc.
> Pete's Blue Celadon =5E 10 Red. (from Sam Clarkson)
>
> Custer (Potash) Feldspar 25.0
> Whiting 20.0
> Grolleg Kaolin 20.0
> Flint 35.0
> Add :
> Tin Oxide 1.0
> Barium Carbonate 2.0
> Barnard Clay 3.0
> I'm using a domestic porcelain. The glaze fires well from cone 9 to a pretty
> hard 10.
> I'm very careful about dust on the rims. Can't figure out why it happens...a
> bit like Russian Roulette.
> Anybody have any ideas?
> Thanks!
> Lois
>
> ______________________________________________________________________________
> 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.
>
John Weber on tue 21 nov 00
Chappell's Clay and Glazes would indicate the cure for crawling lies in
either applying the glaze too thickly (if you dip and let the drops end up on
the lip) or the clay content is too high (suspicious in this glaze), and of
course you should try to remember whether or not you ever pickup the piece
with oily or waxy fingers or by some other means left the lip dirty. Good
luck.
Ron Roy on tue 21 nov 00
Hi Lois,
I'm just very busy these days so I wait to see if anyone else answers first.
Two possible answers - add bentonite to the glaze to make it tougher -
remember - all glazes crack up to some extent on sintering - most of those
cracks heal over due to the natural affinity of glazes to itself when
molten. Adding bentonite sometimes helps stop the cracking by making the
raw glaze stronger. I could also make the glaze less stiff so the glaze
would flow back together at the top of the firing. You might also try a
longer soak at the end to give the glaze more opportunity to get back
together.
Same glaze with Bentonite
Custer - 25.0
Whiting - 20.5
Grolleg - 19.5
Silica - 35.0
Bentonite - 2.0
Some clays have soluble salts in them - either added or there in the raw
materials. When a pot dries these salts migrate to the rim (if the pot is
fired upright) - when bisque fired these salts can help melt the clay more.
This can interfere with glaze adhesion. You can try drying your ware upside
down so the salts will be where there is no glaze.
RR
>This is a great blue celadon, with the exception that from time to time I get
>tiny bits of crawling on the rims of mugs, bowls, etc.
>Pete's Blue Celadon =5E 10 Red. (from Sam Clarkson)
>
>Custer (Potash) Feldspar 25.0
>Whiting 20.0
>Grolleg Kaolin 20.0
>Flint 35.0
>Add :
>Tin Oxide 1.0
>Barium Carbonate 2.0
>Barnard Clay 3.0
>I'm using a domestic porcelain. The glaze fires well from cone 9 to a pretty
>hard 10.
>I'm very careful about dust on the rims. Can't figure out why it happens...a
>bit like Russian Roulette.
>Anybody have any ideas?
>Thanks!
>Lois
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
David Hewitt on tue 21 nov 00
Hello Lois,
I wonder if the surface tension is too low. I must confess that I have
not had to try and solve such a problem as you describe, but the flow of
glazes is affected by the surface tension and the angle of contact,
hence why perhaps it is the rim that is the problem area.
On my calculation your base recipe comes out with a surface tension of
383 dyne/cm at 900oC, but this is reduced by 4 for every 100oc above
this temperature. At cone 9 to 10 this may down to 367.
I read that Tin, Barium and Alumina will tend to increase surface
tension. Perhaps increasing these amounts in your recipe would help.
I would be interested in hearing from anyone, who has had direct
experience of solving such a problem as you describe, to hear if what I
have said is likely to be on the right lines.
David
In message , Lois Atherton writes
>Hi Connie,
>No, I haven't had anyone reply to my question, so I'll ask again.
>This is a great blue celadon, with the exception that from time to time I=
> get
>tiny bits of crawling on the rims of mugs, bowls, etc.
>Pete's Blue Celadon =3D5E 10 Red. (from Sam Clarkson)
>
>Custer (Potash) Feldspar 25.0
>Whiting 20.0
>Grolleg Kaolin 20.0
>Flint 35.0
>Add :
>Tin Oxide 1.0
>Barium Carbonate 2.0
>Barnard Clay 3.0
>I'm using a domestic porcelain. The glaze fires well from cone 9 to a pr=
>etty
>hard 10.
>I'm very careful about dust on the rims. Can't figure out why it happens=
>...a
>bit like Russian Roulette.
>Anybody have any ideas?
>Thanks!
>Lois
--
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP18 3DQ, UK. Tel:- +44 (0) 1633 420647
FAX:- +44 (0) 870 1617274
Web site http://www.dhpot.demon.co.uk
Paul Taylor on thu 23 nov 00
Lois.
There is are mountains of shards in china. The piles are made up of mainly
broken saggars but the rest is a memorial to the crawled and pin holed
glaze. I doubt whether the Chinese were so stupid as to repeat the same
mistake unnecessarily .I reckon it was the price they paid for the glaze
quality they were after.
If your glaze has a marble like quality, a fat unctious look, you are on
the cusp of crawling . Industries pale water or crystal mats do not have
that trouble.
It is difficult to correct the fault without destroying the glaze. You
can guru around with the formula and recipe all you like but you will come
back to the same problem every time the glaze starts to look right.
What is happening as you probably know is that the glazes viscosity is
too high so any fault in the surface of the glaze will not heal over but
tend to form a crawl especially if you under fire it a little . The faults
happen where the rims and changes of direction in the pot occur, because
when it dries the glaze shrinks . Small cracks appear in the glaze coat some
you can see most you can not. these cracks are the fault lines that the
glaze can not bridge because of surface tension .
To stop this you can take some water out of the glaze after de
floculating it . It makes the glaze a B to put on, running and dripping
having to keep it stired, but it does help because the glaze shrinks less -
no cracks.
Calcining the clay ingredients also helps -less shrinkage use say 18 %
+ of molocite instead or a mixture of molocite and china clay ajust for loss
on ignition.
Using walistonite instead of whiting and a % of quarts may help I do no
know why .Theory ( Less raw matirial loss on firing and better glaze
reaction ie more melt but the same crystallization potential keeping the
glaze depth).
Decreasing the surface tension on the rims with a misting of a less
viscose glaze sprayed over the glaze coat on the offending parts of the
pot.
Dipping the pot and spraying the extra thickness. You have noticed
these Glazes work best thick and thick glazes tend to run or crawl but
laminating the layers helps - do not over wet the pot when spraying the
second coat.
Raw glazing the pot .
Raw glazing half the thickness of the glaze and then the rest after
biscuit . it maybe only necessary to spray a thin raw glaze to get suitable
laminasions to stop the crawling.
Remember that the more viscose glaze goes underneath unless you are
making a decoration out of the crawling.
Take some glaze and grind it for a day in a ball mill 10 hours plus
spray a thin coat on offending surfaces.
De flocculate the glaze then separate it out and put the heavy
particles on dipped, then spray or dip the light thin particles on top of
firstly a fresh batch of glaze or the heavier particle glaze.
Try the first suggestion first and the last in desperation.
That's all .tell me how it goes .
Remember some glaze faults are the product of a series of small sins
but glazing with out sin is lifeless - ask the chinese.
Regards from Paul Taylor
http://www.anu.ie/westportpottery
> From: Lois Atherton
> Reply-To: Ceramic Arts Discussion List
> Date: Mon, 20 Nov 2000 09:29:01 EST
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: Glaze Problem
>
> Hi Connie,
> No, I haven't had anyone reply to my question, so I'll ask again.
> This is a great blue celadon, with the exception that from time to time I get
> tiny bits of crawling on the rims of mugs, bowls, etc.
> Pete's Blue Celadon =5E 10 Red. (from Sam Clarkson)
>
> Custer (Potash) Feldspar 25.0
> Whiting 20.0
> Grolleg Kaolin 20.0
> Flint 35.0
> Add :
> Tin Oxide 1.0
> Barium Carbonate 2.0
> Barnard Clay 3.0
> I'm using a domestic porcelain. The glaze fires well from cone 9 to a pretty
> hard 10.
> I'm very careful about dust on the rims. Can't figure out why it happens...a
> bit like Russian Roulette.
> Anybody have any ideas?
> Thanks!
> Lois
>
> ______________________________________________________________________________
> 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 fri 24 nov 00
This is not altogether true - part of the answer here is to replace some or
all of the clay in the glaze with others that have a higher MOR (modulus of
rupture) this makes the dry glaze tougher and less likely to crack in the
first place.
We assume that ware is allowed to dry completely before firing if crawling
is a problem.
Most texts blame shrinkage of raw clay in the recipe for the fault and in
many cases it is simply the poor drying strenght of the clay itself that is
the problem.
The fist step is to replace all or some of the kaolin with ball clay -
using calculation software is the most accurate way to do this. Chosse the
replacement clay according to MOR - should be available from your supplier
- if not then from the mine. If the problem is not solved the next step
would be to add some bentonite.
RR
> It is difficult to correct the fault without destroying the glaze. You
>can guru around with the formula and recipe all you like but you will come
>back to the same problem every time the glaze starts to look right.
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
Paul Taylor on sat 25 nov 00
Dear Ron
In general terms you are right .
But These reduction blues and blue green celadons are reliant on a lack
of titanium for their color. Ball clays and most bentonites are high enough
in titanium to change the delicate glaze color which is the whole point of
these glazes.
I presumed that it was not glaze strength that was causing the problem
because the amount of china clay in the glaze is high enough for good glaze
strength. I also presumed that the quality and fineness of the china clay
was good enough because the glaze was showing the right color.
It was the position of the crawling that led me to believe it was a
shrinkage problem because the glaze was crawling where two plains meet at
the rims and under the rims. Crawling caused by lack of glaze strength is
usually all over the pot. However over wetting of thin rims can show
crawling in glazes with low strength as well as high shrinkage the former
gives crawls in all directions the latter the crawling tends to follow the
form.
These glazes are usually dipped very thick to give the depth needed to
show their color so you could be right if the china clay used is very course
glazing very thick can make the glaze to have shrinkage cracks as well as
weak glaze strength cracks that is why I suggested laminating the glaze. It
is amazing how many faults from pin holing crawling to crazing laminating a
glaze will cure - in glazes over 0.4 millimeters thick. Although I use
standard porcelain china clay I believe Grelog to be one of the best china
clays.
If you are right! the glaze may not be too changed by adding 3 % of
white bentonite or better some gum arabic or one of the products that stop
glazes dusting. the former will affect the titanium content but the latter
will not. Some I have seen on the list recommend corn syrup but I do not
know what that is. Is it the same as golden syrup that Tate and Lyle make
that we used to call it treacle?
I am presuming that the barium in the glaze enhances the color I would
like to know why but I doubt if it counteracts the presents of titanium.
There I could be wrong and ball clay could be substituted. If I am right you
will get green not blue from the glaze.
There are recipes of this glaze (Iron Blue) that do crawl from glaze
weakness but these recipes contain no clay worth speaking of - again to cut
down on the titanium content - those glazes fall off in your hands when
touched which is easily noticed.
Also I think too great a percentage of course frit in earthen ware and
mid fire range is where you find low glaze strength crawling more than in a
stoneware glaze.
I could be wrong because that's how I learned all this.
Regards from Paul Taylor
http://www.anu.ie/westportpottery
> From: Ron Roy
> Reply-To: Ceramic Arts Discussion List
> Date: Fri, 24 Nov 2000 15:48:23 -0500
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: Re: Glaze Problem
>
> This is not altogether true - part of the answer here is to replace some or
> all of the clay in the glaze with others that have a higher MOR (modulus of
> rupture) this makes the dry glaze tougher and less likely to crack in the
> first place.
>
> We assume that ware is allowed to dry completely before firing if crawling
> is a problem.
>
> Most texts blame shrinkage of raw clay in the recipe for the fault and in
> many cases it is simply the poor drying strenght of the clay itself that is
> the problem.
>
> The fist step is to replace all or some of the kaolin with ball clay -
> using calculation software is the most accurate way to do this. Chosse the
> replacement clay according to MOR - should be available from your supplier
> - if not then from the mine. If the problem is not solved the next step
> would be to add some bentonite.
>
> RR
>
>
>> It is difficult to correct the fault without destroying the glaze. You
>> can guru around with the formula and recipe all you like but you will come
>> back to the same problem every time the glaze starts to look right.
>
> Ron Roy
> 93 Pegasus Trail
> Scarborough
> Ontario, Canada
> M1G 3N8
> Evenings 416-439-2621
> Fax 416-438-7849
>
> ______________________________________________________________________________
> 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 26 nov 00
Hi Paul,
The point I am trying to make is - make the glaze tougher - and there are
many ways to do that. CMC gum will do it, soluble satts will as well - Corn
Syrup is another - same as dissolving suger in water and adding it to a
glaze - honey will work as well. The trouble with sugar is - you are
feeding the bacteria and the smell gets pretty bad.
Different kaolins have different MORs - perhaps that would be enough to
turn the corner. If you are using a North American kaolin chances are you
already have plenty if TiO2 anyway - Grolleg and other Englisg kaolins have
low TiO2.
Adding 2% bentonite - even if it does have some TiO2 present - will not add
enough TiO2 to a glaze to be noticed.
All these questions are easily answered by doing some easy tests - we can
talk about it for ever and no one will be the wiser.
RR
> But These reduction blues and blue green celadons are reliant on a lack
>of titanium for their color. Ball clays and most bentonites are high enough
>in titanium to change the delicate glaze color which is the whole point of
>these glazes.
>
> I presumed that it was not glaze strength that was causing the problem
>because the amount of china clay in the glaze is high enough for good glaze
>strength. I also presumed that the quality and fineness of the china clay
>was good enough because the glaze was showing the right color.
>
> It was the position of the crawling that led me to believe it was a
>shrinkage problem because the glaze was crawling where two plains meet at
>the rims and under the rims. Crawling caused by lack of glaze strength is
>usually all over the pot. However over wetting of thin rims can show
>crawling in glazes with low strength as well as high shrinkage the former
>gives crawls in all directions the latter the crawling tends to follow the
>form.
>
> These glazes are usually dipped very thick to give the depth needed to
>show their color so you could be right if the china clay used is very course
>glazing very thick can make the glaze to have shrinkage cracks as well as
>weak glaze strength cracks that is why I suggested laminating the glaze. It
>is amazing how many faults from pin holing crawling to crazing laminating a
>glaze will cure - in glazes over 0.4 millimeters thick. Although I use
>standard porcelain china clay I believe Grelog to be one of the best china
>clays.
>
> If you are right! the glaze may not be too changed by adding 3 % of
>white bentonite or better some gum arabic or one of the products that stop
>glazes dusting. the former will affect the titanium content but the latter
>will not. Some I have seen on the list recommend corn syrup but I do not
>know what that is. Is it the same as golden syrup that Tate and Lyle make
>that we used to call it treacle?
>
> I am presuming that the barium in the glaze enhances the color I would
>like to know why but I doubt if it counteracts the presents of titanium.
>There I could be wrong and ball clay could be substituted. If I am right you
>will get green not blue from the glaze.
>
> There are recipes of this glaze (Iron Blue) that do crawl from glaze
>weakness but these recipes contain no clay worth speaking of - again to cut
>down on the titanium content - those glazes fall off in your hands when
>touched which is easily noticed.
>
> Also I think too great a percentage of course frit in earthen ware and
>mid fire range is where you find low glaze strength crawling more than in a
>stoneware glaze.
>
> I could be wrong because that's how I learned all this.
>
> Regards from Paul Taylor
>http://www.anu.ie/westportpottery
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
Snail Scott on sun 26 nov 00
My dictionary lists 'treacle' as the British word for what
Americans call 'molasses'. This is a byproduct of the sugar
refining process, by the way. Corn syrup is made from
cornstarch; Karo is a common brand name in supermarkets.
Although I've never tried it, I would think that molasses
(treacle) would be an adequate substitute, but much more
expensive. The goal is simply to add lots of sugar in a
convenient liquid form. I've also used confectioners' sugar
added to the dry mix.
-Snail
At 08:12 PM 11/25/00 +0000, you wrote:
> Some I have seen on the list recommend corn syrup but I do not
>know what that is. Is it the same as golden syrup that Tate and Lyle make
>that we used to call it treacle?
> Regards from Paul Taylor
>http://www.anu.ie/westportpottery
>
Gary Elfring on wed 4 apr 01
I'm working with a recreation of a Chinese Celadon
(Celadon Blues book) and I have gotten something that
looks just the way I want it. This glaze has a satin
finish- not high gloss but not a mat finish either.
It is also opalescent. It works very well on carved
or inscribed porcelain. I fire to cone 10 reduction.
The glaze is:
K4 Feldspar 50%
Silica 30%
Whiting 20%
Red Iron Oxide 1.6 - 2.2%
The glaze has two problems that I would like to resolve.
1) I spray the glaze (to control thickness) and once
the glaze dries it comes off the pot *very* easily. No
other glaze I use comes off this easily. (Not flaking off,
just not having any cohesion.) I need to fix this first.
I have mixed in a bit of white glue, which fixes the problem
but the glaze won't keep when you do that and it aggravates
problem 2.
2) The glaze likes to quickly settle into a lump at the bottom
of the bucket.
Any solutions that won't change the look of the glaze?
Gary
ge@elfring.com
Taylor Hendrix on tue 22 oct 02
Hello all,
I have a question for all the glaze wizzes on list. My teacher and I have
noticed a drastic change in one of her staple glazes over the last two firings
of her kiln. We fire ^6. I give the glaze particulars below. This "Blue Hair's
Fur" glaze's usual result is a nice deep varigated blue with some dark brown
breaking. Nice. Lately, however, the glaze is giving us a green with
varigated blue and no breaking. We have both used this glaze in the past
over a light and dark body with regular results.
The two possible causes that came to mind are fire schedule changes (She
got RR's glaze book--eg. end soak) and contamination. Now, I am a
bit "spontaneous" when it comes to glazing, but I think I would have noticed
any cross contamination. Could the age of the glaze batch be a factor?
Mixing is probably not the problem in this case.
Thanks for taking a crack at this for me.
Blue Hare's Fur
Neph Sye 47.3
Gerstley Borate 27
Silica 20.30
EPK 5.4
bentonite 2.0
Add:
Red Iron Oxide 2.0
Cobalt Oxide 1.0
Rutile 4.0
Taylor, in soggy Waco
Ababi on wed 23 oct 02
A few weeks ago, someone or more, wrote, that this glaze, in it's more favorite name,
floating blue - worked good ONLY in fast cooling. If you adopt R&J ways, do it to their
glazes or at least check to which glazes it does work. If you do the slow cooling
consider using one of the glazes I offered in the last PMI as the first level in my
combination Koren27/1 or two
See here
http://members4.clubphoto.com/ababi306910/912566/
I tested lately as a second layer the floating blue, I changed the rutile into titanium,
was nice but not nice enough.
Ababi
---------- Original Message ----------
>Hello all,
>I have a question for all the glaze wizzes on list. My teacher and I have
>noticed a drastic change in one of her staple glazes over the last two firings
>of her kiln. We fire ^6. I give the glaze particulars below. This "Blue Hair's
>Fur" glaze's usual result is a nice deep varigated blue with some dark brown
>breaking. Nice. Lately, however, the glaze is giving us a green with
>varigated blue and no breaking. We have both used this glaze in the past
>over a light and dark body with regular results.
>The two possible causes that came to mind are fire schedule changes (She
>got RR's glaze book--eg. end soak) and contamination. Now, I am a
>bit "spontaneous" when it comes to glazing, but I think I would have noticed
>any cross contamination. Could the age of the glaze batch be a factor?
>Mixing is probably not the problem in this case.
>Thanks for taking a crack at this for me.
>Blue Hare's Fur
>Neph Sye 47.3
>Gerstley Borate 27
>Silica 20.30
>EPK 5.4
>bentonite 2.0
>Add:
>Red Iron Oxide 2.0
>Cobalt Oxide 1.0
>Rutile 4.0
>Taylor, in soggy Waco
>______________________________________________________________________________
>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.
Christena Schafale on wed 23 oct 02
It's the firing schedule. Your glaze is the (in)famous Floating Blue, and
it hates to be fired too long/slow -- will turn greenish everytime. Been
there, hammered those pots.
Chris
At 09:52 PM 10/22/02 -0400, you wrote:
>Hello all,
>
>I have a question for all the glaze wizzes on list. My teacher and I have
>noticed a drastic change in one of her staple glazes over the last two firings
>of her kiln. We fire ^6. I give the glaze particulars below. This "Blue
>Hair's
>Fur" glaze's usual result is a nice deep varigated blue with some dark brown
>breaking. Nice. Lately, however, the glaze is giving us a green with
>varigated blue and no breaking. We have both used this glaze in the past
>over a light and dark body with regular results.
>
>The two possible causes that came to mind are fire schedule changes (She
>got RR's glaze book--eg. end soak) and contamination. Now, I am a
>bit "spontaneous" when it comes to glazing, but I think I would have noticed
>any cross contamination. Could the age of the glaze batch be a factor?
>Mixing is probably not the problem in this case.
>
>Thanks for taking a crack at this for me.
>
>Blue Hare's Fur
>
>Neph Sye 47.3
>Gerstley Borate 27
>Silica 20.30
>EPK 5.4
>bentonite 2.0
>Add:
>Red Iron Oxide 2.0
>Cobalt Oxide 1.0
>Rutile 4.0
>
>
>Taylor, in soggy Waco
>
>______________________________________________________________________________
>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.
Consultation and Referral Specialist
Resources for Seniors
christenas@rfsnc.org
http://www.resourcesforseniors.com
Phone: (919) 713-1537
FAX: (919) 872-9574
1110 Navaho Dr, Suite 400
Raleigh, NC 27609
Craig Edwards on wed 23 oct 02
Hello Taylor: My first thought is that your problem is with the Gerstley
Borate. It is known to change radically from batch to batch. I don't use it
any more but sub in Frits to get the boron content in the glaze. It is also
slightly soluble so that you can lose some of it though evaporation. Even
if the G Borate is not the problem in this instance. I would reformulate
with a frit for future happiness.
Just my take. Good luck.
Craig Edwards
Back in New London MN
>Hello all,
>
>I have a question for all the glaze wizzes on list. My teacher and I have
>noticed a drastic change in one of her staple glazes over the last two
>firings
>of her kiln. We fire ^6. I give the glaze particulars below. This "Blue
>Hair's
>Fur" glaze's usual result is a nice deep varigated blue with some dark
>brown
>breaking. Nice. Lately, however, the glaze is giving us a green with
>varigated blue and no breaking. We have both used this glaze in the past
>over a light and dark body with regular results.
>
>The two possible causes that came to mind are fire schedule changes (She
>got RR's glaze book--eg. end soak) and contamination. Now, I am a
>bit "spontaneous" when it comes to glazing, but I think I would have
>noticed
>any cross contamination. Could the age of the glaze batch be a factor?
>Mixing is probably not the problem in this case.
>
>Thanks for taking a crack at this for me.
>
>Blue Hare's Fur
>
>Neph Sye 47.3
>Gerstley Borate 27
>Silica 20.30
>EPK 5.4
>bentonite 2.0
>Add:
>Red Iron Oxide 2.0
>Cobalt Oxide 1.0
>Rutile 4.0
>
>
>Taylor, in soggy Waco
>
>______________________________________________________________________________
>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.
_________________________________________________________________
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Autumn Downey on wed 23 oct 02
Yes, good old floating blue. We get best results at cone 5; at 6 it will
blister and be greener. So, it does seem to be different in different places.
Alot of people have mentioned that rutile is not always the same. Have you
by any chance started using a new batch of rutile? (Nepheline syenite is
also being discussed as a variable material, it seems.)
You might try adding about 3-5% talc to the glaze - do a small experiment
first with about 2/3 cup of glaze. Think we found that the Mg would at
least strengthen the blue. It will be different but might save the batch.
Autumn Downey
Arcola, Saskatchewan
At 06:59 AM 10/23/02 -0500, you wrote:
>Hello Taylor: My first thought is that your problem is with the Gerstley
>Borate. It is known to change radically from batch to batch. I don't use it
>any more but sub in Frits to get the boron content in the glaze. It is also
>slightly soluble so that you can lose some of it though evaporation. Even
>if the G Borate is not the problem in this instance. I would reformulate
>with a frit for future happiness.
>Just my take. Good luck.
>
>Craig Edwards
>Back in New London MN
>
>
>
>
>
>
>
>
>>Hello all,
>>
>>I have a question for all the glaze wizzes on list. My teacher and I have
>>noticed a drastic change in one of her staple glazes over the last two
>>firings
>>of her kiln. We fire ^6. I give the glaze particulars below. This "Blue
>>Hair's
>>Fur" glaze's usual result is a nice deep varigated blue with some dark
>>brown
>>breaking. Nice. Lately, however, the glaze is giving us a green with
>>varigated blue and no breaking. We have both used this glaze in the past
>>over a light and dark body with regular results.
>>
>>The two possible causes that came to mind are fire schedule changes (She
>>got RR's glaze book--eg. end soak) and contamination. Now, I am a
>>bit "spontaneous" when it comes to glazing, but I think I would have
>>noticed
>>any cross contamination. Could the age of the glaze batch be a factor?
>>Mixing is probably not the problem in this case.
>>
>>Thanks for taking a crack at this for me.
>>
>>Blue Hare's Fur
>>
>>Neph Sye 47.3
>>Gerstley Borate 27
>>Silica 20.30
>>EPK 5.4
>>bentonite 2.0
>>Add:
>>Red Iron Oxide 2.0
>>Cobalt Oxide 1.0
>>Rutile 4.0
>>
>>
>>Taylor, in soggy Waco
>>
>>__________________________________________________________________________
____
>>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.
>
>
>_________________________________________________________________
>Surf the Web without missing calls! Get MSN Broadband.
>http://resourcecenter.msn.com/access/plans/freeactivation.asp
>
>___________________________________________________________________________
___
>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.
>
iandol on thu 24 oct 02
Dear Taylor Hendrix,
I think if you diminish the quantity of Rutile you will bring this glaze =
back to the blue part of the spectrum.
There was considerable discussion about the production of Green from =
Cobalt compounds. One of the most prominent suggestions was to =
incorporate Rutile in the recipe to achieve the colour shift from blue =
to green.
Have you changed your source of Rutile recently. If you have, then try =
to get the analyses for before and after.
Best regards,
Ivor Lewis. Redhill, South Australia.
Conrad Krebs on sat 25 sep 04
Hello Clayarters,
I am trying to apply glazes of two different colors (identical base glazes,
one batch with one color Mason stain mixed in, the second batch with a
different color mixed in, call them glazes A and B) to a bisque piece. I am
spraying glaze A onto the entire surface of the piece. I then take a pocket
knife and scrape glaze A off of the part that I want to apply glaze B to.
With a brush I then brush glaze B onto that part. I then fire the piece
after it's dried. My problem is that I get a ragged line where glazes A and
B meet. I have been following the discussion thread regarding latex resist
and thought I'd give that a try. Any other suggestions as to how I might
smooth out the ragged line?
Thanks, Conrad
Pfeiffer Fire Arts on sat 19 jul 08
We have 10 gallons of a cobalt glaze that we
having been having a problem with. At first after
we mixed it up we set the specific gravity to 1.5.
It was too thin and settled badly so I added Epsom
salts and this fixed it up for a few weeks. Then
it for some unknown reason get thicker, turned to
almost a solid, think thick cake frosting. No
problem I say add sodium silicate and soda ash.
Needed to add a lot of fix this and was having
very little effect until we added more
water,SG1.44, and made it back to an ok glaze.
After a few days it is now too thin and making
rock on the bottom of the bucket. I then let it
evaporate back some and now the SG is 1.48 but
still too thin. The only thing I can think of is
to add more Epsom salts and try to very slowly try
to undo the sodium silicate.
Any clue as to what is happening? Our other glazes
make from the same base all needed a little ES but
have not gotten thicker with time. Our glazes have
lots of clay (13%) and 2% Bentonite and .5% CMC.
Anyone else have a similar problem? Will adding
more Epsom salts work? What is the limit on how
much you can go back and forth on flocculating and
unflocculating a glaze.
Thanks
Dan & Laurel in Elkmont Al
www.pfeifferFireArts.com
Lee Love on tue 22 jul 08
Ron is mistaken about washing. It is not just pouring water off.
Actually, you might not have water to pour off. To actually wash the
glaze, you might have to add water, mix and then let it settle. THEN
pour the water off. If it doesn't change, you may have to add water,
let settle and pour again.
Can you share what is in the glaze?
I just poured off the top of two ash glazes I mixed up:
Briscoe's (he uses over white slip) and a Sander's Tamba. The water
is the color of coffee. I will add the water back to the Tamba, but
I might add new water to the Briscoe's. He uses it thin. I want it
a little thicker to show green.
--
Lee Love in Minneapolis
http://mashikopots.blogspot.com/
http://claycraft.blogspot.com/
"Let the beauty we love be what we do.
There are hundreds of ways to kneel and kiss the ground." --Rumi
Ron Roy on wed 23 jul 08
Hi Dan & Laurel,
Sounds like you added to much in both cases - when you add too much
flocculant you can get the opposite effect - same with a deflocculante.
Try washing the glaze before adding the right chemical - drain off water
and replace with new water a few times to get rid of the salts.
You could also use Darvan instead of sodium silicate and soda ash - Darvan
is more tolerant if you use too much.
Add small amounts - stir - let sit for a while - drops rather than cupfuls
for dealing with buckets of glazes. Once you get used to them you can get
braver.
RR
>We have 10 gallons of a cobalt glaze that we
>having been having a problem with. At first after
>we mixed it up we set the specific gravity to 1.5.
>It was too thin and settled badly so I added Epsom
>salts and this fixed it up for a few weeks. Then
>it for some unknown reason get thicker, turned to
>almost a solid, think thick cake frosting. No
>problem I say add sodium silicate and soda ash.
>Needed to add a lot of fix this and was having
>very little effect until we added more
>water,SG1.44, and made it back to an ok glaze.
>After a few days it is now too thin and making
>rock on the bottom of the bucket. I then let it
>evaporate back some and now the SG is 1.48 but
>still too thin. The only thing I can think of is
>to add more Epsom salts and try to very slowly try
>to undo the sodium silicate.
>
>Any clue as to what is happening? Our other glazes
>make from the same base all needed a little ES but
>have not gotten thicker with time. Our glazes have
>lots of clay (13%) and 2% Bentonite and .5% CMC.
> Anyone else have a similar problem? Will adding
>more Epsom salts work? What is the limit on how
>much you can go back and forth on flocculating and
>unflocculating a glaze.
>
>Thanks
>
>
>Dan & Laurel in Elkmont Al
>www.pfeifferFireArts.com
Ron Roy
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Des & Jan Howard on fri 21 aug 09
Dave
Get a spritzer spray bottle, make a mix of water/
methylated spirits 2:1.
Spritz the glaze in the drum before dipping.
Spray your bubbles away.
Also works for de-frothing plaster.
Des
Dave Lyons wrote:
> Can anyone help me fix a batch of glaze that I've over deflocculated? It=
is
> frothy and leaves hundreds of tiny bubbles when I dip a pot in it. Is th=
ere
> an easy fix? Even a not so easy fix would be appreciated. It is a cone =
6
> glaze found in Bill vanGilder's book called Nutmeg. The last batch I mad=
e I
> didn't use the bentonite and added Flocs instead. This time I used both.
> Not recommended!
--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850
02 6373 6419
www.luepottery.hwy.com.au
-32.656072 149.840624
lili krakowski on fri 21 aug 09
Well! So fleecy Flocs your glaze adorn....
The only thing I can think of is rinsing the glaze. Add lot of water, =3D
stir well, let sit overnight, syphon off water. Add lots of water, stir =
=3D
well, et sit overnight, syphon off water...
That is how the water soluble materials in woodash are removed. It =3D
should work here...assuming Flocs is water soluble....
Lili Krakowski
Be of good courage
Bonnie Hellman on fri 21 aug 09
Dave,
I've had a problem with one glaze (Pete Pinnell's weathered bronze) leaving
lots of tiny bubbles that "pop" in the firing, leaving tiny round unglazed
areas amidst the fired glaze.
My solution has been to make a VERY dilute bit of that glaze, and pour it o=
n
my pots to be glazed. Then I apply the normal thickness of the glaze.
Maybe this would work for you.
Bonnie
Bonnie Hellman
Ouray, Colorado 81427
----- Original Message -----
From: "Dave Lyons"
To:
Sent: Thursday, August 20, 2009 4:08 PM
Subject: Glaze problem
> Can anyone help me fix a batch of glaze that I've over deflocculated? It
> is
> frothy and leaves hundreds of tiny bubbles when I dip a pot in it. Is
> there
> an easy fix? Even a not so easy fix would be appreciated. It is a cone =
6
> glaze found in Bill vanGilder's book called Nutmeg. The last batch I mad=
e
> I
> didn't use the bentonite and added Flocs instead. This time I used both.
> Not recommended!
> Dave Lyons
ivor & olive lewis on sat 22 aug 09
Dear Dave Lyons,
A lot will depend on the type and quantity of deflocculating agent you used=
.
The excessive frothing may be due to one of the ingredients in the glaze. S=
o
it seems as thought you have two problems to solve
1 Reducing the degree of Deflocculation.
2 Eliminating the cause of the frothing
Since vanGilders book is not readily available perhaps you could list the
ingredients and list your deflocculants.
Best regards,
Ivor Lewis,
Redhill,
South Australia
Lili Krakowski on tue 28 feb 12
Robert:=3D20
As I do not have a digital kiln, I cannot address what might be related =3D
to your firing schedule.
So I address only "basics":
From the pictures you posted it looks as though a few large blisters had =
=3D
formed, and then not healed over. As the blisters are few and far =3D
between, my first guess is that something in your clay body is gassing =3D
off late in the cycle--and the glaze did not run and seal it over. =3D
Maybe the glaze application has been too thin, or maybe the glaze is =3D
just not quite fluid enough.(Common with mattes) Here is another reason =
=3D
to have test tiles of at least two bodies besides the one being used for =
=3D
the pots: to be able to see if the cause of the problem might be the =3D
body. And on these test tiles one can test for desirable thickness of =3D
application.
As to pinholing. Again it can be caused by the nature of the clay body. =
=3D
You say you mix it yourself, so you can, probably, fix it. Pinholing =3D
can be caused by too thin, or too thick application of glaze. Are you =3D
getting pinholes on the glaze surface when you apply the glaze? If so =3D
you might try a damper bisque, a more fluid glaze, or jockeying a bit =3D
with the additives--Bentonite and calcium chloride or magnesium =3D
sulphate. I am told some commercial additives can cause pinholing, but =3D
I know nothing about them.=3D20
Spraying glaze also can result in application problems that lead to =3D
p.h....But I do not know about sprayed glazes.=3D20
Last: for the glaze you make yourself: replacing high gassing =3D
ingredients such as whiting by low gassing ones such as Wollastonite can =
=3D
help.
Lili Krakowski
Be of good courage
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