johnd@ebi.com on thu 21 nov 96
hi all,
i made up a large batch of this albany glaze i got from
chappel's book after making and testing a small batch.
moss brown albany cone 6 oxidation
albany 89
lith carb 9
mag carb 2
bent 1
the test tile was fine, really nice. when i fired larger pieces
(the clay is byrne's sandy white, no grog) there was an
amount of shivering. the glaze only shivered from the rim of
some vases and the top of a handle.
being that albany is powdered gold and i have a VERY
limited supplyt, i would like to save this glaze. does anyone
have a suggestion as to what can be added (as nothing can
be removed) to this glaze to stop this problem?
thanx,
john
johnd@ebi.com
looking out over the entire island of manhattan from the 84th floor of the
world trade center.
Autumn Downey on fri 22 nov 96
Hello John,
It might not be your Albany that is the problem as I've found that lithium
seems to cause shivering - as you say, on rims. If anyone has suggestions,
solutions, I'd be interested, too, as I try lithium glaze tests on and off
(literally).
Autumn Downey
Tony Hansen on sat 23 nov 96
>albany 89
>lith carb 9
>mag carb 2
>bent 1
>the glaze only shivered from the rim of some vases and the top of a handle.
This glaze is very DANGEROUS. If anyone ever swallowed one of those glaze flakes
is would be a disaster. When shivering shows up it does not mean the glaze is 'a
little low in expansion' it means it is way too low. This recipe is a classic fo
this problem. The lithium must be dropping considerably and you must introduce
some K2O or Na2O to raise the expansion. Unfortunately these changes may
compromize the visual character.
--
Tony Hansen, IMC - Pulishers of INSIGHT, FORESIGHT, Magic of Fire
134 Upland Dr., Medicine Hat, Alta T1A 3N7 Canada
Phone:403-527-2826 FAX:527-7441 email: thansen@mlc.awinc.com
web: http://digitalfire.com/imc.html
Craig Martell on sat 23 nov 96
Hi John: I responded to another post sometime back that was basically the
same kind of problem, involving Lithium. Your albany glaze doesn't fit the
claybody you are using. It (the glaze), is under too much compression and
that is what is causing the shivering. Lithium has a very low coefficient of
expansion, and is the ingredient in the glaze that is to blame for the
problem. However, it sounds as if the glaze fit is not too far off. One
possible remedy is to try the glaze on different clay bodies. Another remedy
would be to add a high expansion material to the glaze to adjust the fit and
relieve the compression. I would suggest adding Nepheline Syenite to the
glaze at about 5% or less increments until you notice the problem is
corrected. You can withdraw small amounts of the glaze and use Brongniart's
formula to determine the weight of dry materials in your already mixed sample
of the glaze. You can find info on Brongniart's formula in a lot of books on
glazes. Or course, you may already know how to use it and I'm wasting my
breath. The Potter's Dictionary of Materials and Techniques by Frank Hamer
has a great deal of info on the Formula on p. 135.
It is also important to make standing tiles with pronounced edges to apply
the test glazes to. You want to give the glaze EVERY possible chance to
shiver, and flat tiles where the glaze does not wrap around rims and edges
will not tell you what you want to know. I hope this helps, I gotta go
check the Gas Huffer!
Later, Craig Martell-Oregon
Salvador Acosta on sun 24 nov 96
dear john,
i had a glaze that i liked but it also shivered. my glaze had no albany
in it. i tried 2 suggestions from a worshop instructor.
the first was to add liquid starch. i added about 1/4 cup and it
thickened the glaze. when i glazed my ware i had a fairly "dense"
surface when it was dry, it would not powder off if i rubbed it.
fired fine with no shivering and no change in color.
the 2nd suggestion i use now is adding mixed cmc gum to my glaze
and it does the same thing. to make a batch of cmc gum i put 2
teaspoons in a quart cotainer and add 1 cup hot tap water and shake
well. 4 hours later i add 1 more cup hot water and shake. i let this sit
overnight. then i add 2 more cups hot water and shake. it is then ready
to use. add to glaze in small amounts until glaze is a thick
cosistency.
hope this works for you
juliet
texas
SLPBM@cc.usu.edu on mon 25 nov 96
what is liquid starch?
Corn starch?
Starch for clothes/ironing??
Ron Roy on mon 25 nov 96
Just a short addition to Salvador's post - in case anyone thinks adding
starch or CMC gum to a glaze will have any effect on glaze/body fit. Starch
burns off so it is not there to do anything - there is a some sodium in
SCMC gum but not enough to change glaze body fit - not in the quantities we
use.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
Pat Wehrman on tue 26 nov 96
Ron-
How much CMC do you use per 1000 or 5000 gram batch of glaze? We have a
cobalt that is crawling all over the place and we think it is the gum (we put in
alot accidentally). One of our books said putting in gum will keep a glaze from
crawling but didn't say how much to use. It is the same book that said too much
will cause a glaze to crawl. Go fig.
Anyway, TIA.
Pat wehrman@goldrush.com
Tony Hansen on tue 26 nov 96
I hate to be a 'stick-in-the-mud' but I wouldn't use that Albany glaze
without 'major surgery' to its recipe. Shivering glazes are dangerous.
Shivering means something is drastically wrong with the thermal
expansion and only changing the body or changing the glaze recipe deals
with that.
--
Tony Hansen, IMC - Publishers of INSIGHT/FORESIGHT/Magic of Fire
134 Upland Dr., Medicine Hat, Alta T1A 3N7 Canada
Phone:403-527-2826 FAX:527-7441 Web: http://digitalfire.com/imc.html
Craig Martell on tue 26 nov 96
Hello Again: I answered this post a few days ago and, if you all will permit
me, I'll add another $.02. I think that Salvador's post about CMC and starch
additions to glazes were addressing a different problem. The addition of
these two additives will promote better adherence of glazes to RAW or
Bisqueware, and I think there is some confusion as to what Shivering actually
is. Shivering is a glaze FIT problem that reveals itself after the ware has
been fired to maturity. Shivering is the exact opposite of crazing (the
glaze is under too much stress from tension), but in a situation where
Shivering occurs, the glaze is under too much compression and fractures occur
that force the glaze to flake off the pot. I hope I haven't missed the point
here, but I have no reason to think that CMC or Starch additions to a glaze
will correct shivering or influence glaze fit in any way.
Kind Regards, Craig Martell-Oregon
Salvador Acosta on wed 27 nov 96
I use liquid starch for clothes/ironing in a glaze. It works the same
for me as CMC gum.
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