Earl Brunner on sun 9 jul 06
We need the formula Nathan.
"nsmheralds@netzero.net" wrote: I have a glaze that has mysteriously self-thickend. I think I flocculated, but I need to know how if happened or if there are other explanations.
I originally mixed it last November and I've probably stirred it once a month or so when I needed to glaze something with it. A week or so ago, I went to stir it again in order to glaze some pots, only to find that I had an inch or two of water over nearly rock-hard glaze sediment. I thought maybe I hadn't secured the lid well enough and had lost water through evaporation (although the volume looked about the same as what I'd remembered from before). It took at least a good 20 minutes of stirring and scraping and adding water to loosen it all. When I was finished, the volume had increased from maybe 3 gallons to at least 4, maybe 4.5, and the glaze STILL has a consistency somewhere between that of latex paint and thick pudding. I attempted to glaze with it anyway and, as I should have expected, it peeled and crawled.
I'm thinking about adding a deflocculant. Before I do that, I need to know if this is indeed the problem, how it may have happened, which deflocculant to use and how much I should add.
-Nathan Miller
Thistillium Pottery
Newberg, OR
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Earl Brunner
e-mail: brunne53-clayart1@yahoo.com
nsmheralds@netzero.net on sun 9 jul 06
I have a glaze that has mysteriously self-thickend. I think I flocculat=
ed, but I need to know how if happened or if there are other explanation=
s.
I originally mixed it last November and I've probably stirred it once a =
month or so when I needed to glaze something with it. A week or so ago,=
I went to stir it again in order to glaze some pots, only to find that =
I had an inch or two of water over nearly rock-hard glaze sediment. I t=
hought maybe I hadn't secured the lid well enough and had lost water thr=
ough evaporation (although the volume looked about the same as what I'd =
remembered from before). It took at least a good 20 minutes of stirring=
and scraping and adding water to loosen it all. When I was finished, t=
he volume had increased from maybe 3 gallons to at least 4, maybe 4.5, a=
nd the glaze STILL has a consistency somewhere between that of latex pai=
nt and thick pudding. I attempted to glaze with it anyway and, as I sho=
uld have expected, it peeled and crawled.
I'm thinking about adding a deflocculant. Before I do that, I need to k=
now if this is indeed the problem, how it may have happened, which deflo=
cculant to use and how much I should add.
-Nathan Miller
Thistillium Pottery
Newberg, OR
=
Ivor and Olive Lewis on mon 10 jul 06
Dear Nathan Miller,
Sounds as though your glaze has just settled !
Unless you have substances in the recipe that can be deflocculated =
adding a deflocculant will have little effect. Since you do not give an =
indication of the ingredients it would be hard to say if you should.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
=20
John Post on mon 10 jul 06
Hi Nathan,
How much Gerstley Borate is in this glaze? If there is more than 10% it
is the root of your problems.
Send in the recipe to clayart so we can have a look at it.
John Post
Sterling Heights, Michigan
> I have a glaze that has mysteriously self-thickend.
>
Paul Vernier on mon 10 jul 06
Nathan,
I believe you are experiencing the property Thixotropy.
If you stir the glaze you should see a change is viscosity. It will thin
out as the gell effect diminishes.
From the Wikipedia:
Thixotropy is the property of some non-newtonian pseudoplastic fluids to
show a time-dependent change in viscosity; the longer the fluid undergoes
shear, the lower its viscosity.
A good definition in pottery/caly terms can be found in the Potter's
Dictionary by Frank and Janet Hamer.
Or Google for other definitions.
Paul (Santa Cruz, CA)
full text:
http://en.wikipedia.org/wiki/Thixotropic
Nathan Miller on tue 11 jul 06
I apoligize for not including the recipe--I don't know why it didn't occur
to me to do so.
Custer spar 27.26
Whiting 23.28
EPK 14.4
ZnO 3.01
Silica 27.26
Cobalt carb 4.5
Regarding thixotropy, how much would I have to blunge it before determining
whether or not this is the case? Or is there no way to say for sure, short
of constantly blunging it for half an hour?
Nathan Miller
Newberg, OR
Ron Roy on tue 11 jul 06
Hi Nathan,
Beats me - there is nothing in the recipe that I can blame - to flocculate
or deflocculate.
Perhaps there is something in the Cobalt Carb. from processing - that is a
lot of cobalt!
Perhaps you have acidic water and it is getting some of the sodium and
potassium out of the spar.
Why not just add 2% bentonite to your next batch? Dropping 1 EPK will
balance that off.
If you want me to reformulate with ball clay - that will help - but I need
to know what ball clays you have.
RR
>I apoligize for not including the recipe--I don't know why it didn't occur
>to me to do so.
>
>Custer spar 27.26
>Whiting 23.28
>EPK 14.4
>ZnO 3.01
>Silica 27.26
>Cobalt carb 4.5
>
>Regarding thixotropy, how much would I have to blunge it before determining
>whether or not this is the case? Or is there no way to say for sure, short
>of constantly blunging it for half an hour?
>
>Nathan Miller
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Nathan Miller on thu 13 jul 06
On Tue, 11 Jul 2006 22:14:58 -0500, Ron Roy wrote:
>Hi Nathan,
>Perhaps there is something in the Cobalt Carb. from processing - that is a
>lot of cobalt!
True. Cobalt carb is CoCO3, yes? Does the cobalt carb molecule break down
in a glaze slurry? If so, would the resultant release of CO2 do anything to it?
>Perhaps you have acidic water and it is getting some of the sodium and
>potassium out of the spar.
Newberg city water is treated to be pretty darned close to neutral in order
to minimize leaching of metals from pipes.
>Why not just add 2% bentonite to your next batch? Dropping 1 EPK will
>balance that off.
Would bentonite delay this thickening? It acts perfectly normal and behaves
quite well...up until now, that is.
>If you want me to reformulate with ball clay - that will help - but I need
>to know what ball clays you have.
The only ball clay I have is 49er, and I only have about 9lbs of it.
When I went to the studio today, I spent a few minutes just blunging the
snot out of this glaze. It seemed to move okay and with something
approximating the consistency it should, but only while it was in motion.
When I stopped, it would return to its sludgy state, but without settling.
It sort of reminded me of the consistancy of partially congealed Jello or
half-spoiled sour cream. It wasn't thick in the same way that it would be
had I simply had way too little water. The solids seemed to be coming
halfway out of solution and/or suspension and almost seemed to be flowing
around the water, rather than through it.
Now that I think about it, the batches of this glaze we use over at the
local university also do this. However, since there are a lot of students
using it, I've only noticed this when the batch is nearly depleted, which I
always figured had to do with water ratio (students are notorious for doing
things like leaving the lids off the buckets or not thoroughly mixing
glazes). Usually glazes are depleted and remixed on average once per
semester, so the life expectancy of a batch of glaze, especially the popular
royal cobalt (aka "Buy-Me-Blue"), is usually in the vicinity of 4-6 months.
A couple of my glaze buckets, including the one in which this cobalt glaze
resides, are used laundry soap buckets. Although I've well-rinsed these
buckets, could residue have an effect on the glaze? If so, would this
effect be more or less immediate, or might it sneak up on me? Also, neither
or my other glazes, also mixed at the same time, have not shown any signs of
these sorts of suspension issues.
Nathan Miller
Thistillium Pottery
Newberg, OR
Donald Burroughs on sat 15 jul 06
Nathan
I'm betting on those laundry soap buckets. If the soap was liquid it may
have left a residue which has somehow contaminated the plastic of the
pail. Did you know that laundry soap has non swelling bentonite added to
it as a binder? I found out this little bit of trivia when I went to the
Marine Dinosaur Museum in Morden, Manitoba.
Don Burroughs
Nathan Miller on sat 15 jul 06
>I'm betting on those laundry soap buckets. If the soap was liquid it may
>have left a residue which has somehow contaminated the plastic of the
>pail.
It was powdered laundry soap, if that makes a difference. The other two
glazes I have in laudry soap buckets haven't done anything weird, but could
that be because the soaps are different and have different enough
formulations such that the residue from one has this effect and the residue
from the others doesn't?
>Did you know that laundry soap has non swelling bentonite added to
>it as a binder?
Interesting. That sounds like the sort of thing that could make a
difference. I'll try adding Epsom salts as recommended and go from there.
-Nathan Miller
Thistillium Pottery
Newberg, OR
Donald Burroughs on sun 16 jul 06
Hello Nathan
Yes it is powered laundry soap which has the non-swelling bentonite as a
binder, eg.;Tide et al. Also used in toothpaste, diesel engine oil
filters, and is also the sole ingredient used to trap the residue
(fineings) in wine (red or white). If you ever have the chance to make
your own wine or you know somebody who does make observations when the non-
swelling bentonite is added. Even though it known as "non-swelling" it
does absorb moisture,residue and "traps" the finings in wine and will grow
because of this process, but unlike the bentonites of I believe (Utah?) it
does not grow to boulder rock hard like proportions just because there is
moisture available. Non-swelling bentonite (gumbo) of which most of
southern and southwestern Manitoba is comprised underneath the topsoil
simply retains moisture and contributes to poor drainage around house
foundations and can be a real problem in farmer's fields. It is here in
abundance because of the ancient agazziz sea upon which the above regions
of Manitoba sat upon eons ago.
Don Burroughs
Hank Murrow on mon 17 jul 06
On Jul 17, 2006, at 2:02 AM, Donald Burroughs wrote:
> Non-swelling bentonite (gumbo) of which most of
> southern and southwestern Manitoba is comprised underneath the topsoil
> simply retains moisture and contributes to poor drainage around house
> foundations and can be a real problem in farmer's fields. It is here in
> abundance because of the ancient agazziz sea upon which the above
> regions
> of Manitoba sat upon eons ago.
It is useful to know that Montmorillonite (the mineral name for
bentonite, which is a place name) is formed when clay particles deposit
in saline waters. these clays form with an additional lattice of silica
which helps them hold more water, thus the gumbo description. The clays
of the coast range of Oregon are loaded with slimey high fire clays
which tend to crack because of the Montmorillonite content.
Cheers from Eugene,
Hank
www.murrow.biz/hank
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