Alyssa Ettinger on sat 18 nov 06
grrrrrrrr. so my glazes are developing gritty particles that look like sand.
glazes made a year ago, 6 months ago... doesn't matter. grit.
glaze is:
EPK - 15.0
Fusion frit 38 - 33.0
Whiting - 13.5
feldspar - 13.0
Silica - 25.5 (i actually have upped this because of crazing)
plus, i use masons for colorants: from 1-4%.
there doesn't seem to be any correlation between what has more grit vs. what
has more masons. at it seems random as to why some have more than others.
obv, i've sieved them and will do so again if more form. but what are they?
will more come?
alyssa
www.alyssaettinger.com
Edouard Bastarache Inc. on sun 19 nov 06
Hello all,
if Fusion Frit #38 is a high boron frit :
One finds in our trade several types of high boron
frits (one can thus mention Johnson Matthey's frit
#3221, which is very close to an anhydrous calcium
metaborate since its weight composition is roughly
45 % CaO and 55% B2O3).
Glazes made up of such frits sometimes pose a
problem at the time of their conservation in the
wet state for periods ranging from a few days to
several weeks. Small crystals in the shape of
needles or agglomerates appear resembling balls in
the glaze left to rest.
These crystals grow as a function of time until
reaching sometimes a millimeter in size.They
should then be removed by a very fine sieving, if
not these crystals produce bubbles at the time of
firing.
The composition of these crystals resembles that
of colemanite, i.e. calcium borate pentahydrate
(Ca2B6O11 5H2O). This hydrated compound breaks up
releasing its water molecules when the glaze is
already in fusion (glazes designed with this type
of frit are often glazes of low temperature, for
raku or earthenware). The water thus released in
the molten glaze produces bubbles while vaporizing
violently.
After having studied this problem on several
occasions in glazes left unused long enough in the
shop and having tried to cure this problem, the
best solution consisted in blocking the formation
of crystals by using demineralized water instead
of tap water. The glaze batch thus prepared
preserves itself free of crystalline precipitation
and bubbles avoided.
The explanation of this phenomenon is in the
composition of tap water when it is calcareous.
High boron frits not being always very stable, a
small part of the boron is solubilized in the
water of the glaze batch. This soluble boron
combines with the calcium of the calcareous water
forming crystals of hydrated calcium borates.By
removing the calcium ions in water by the use of
demineralized water, this combination cannot occur
anymore and the glaze batch remains clean and can
thus be preserved during weeks.
<
Smart.Consei and I
Edouard Bastarache
Le Français Volant
The Flying Frenchman
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.wanadoo.fr/smart2000/index.htm
http://www.pshcanada.com/Toxicology.htm
http://www.flickr.com/photos/30058682@N00/
Alyssa Ettinger on sun 19 nov 06
also, i add epsom salts to the glazes because there's so much frit.
alyssa
www.alyssaettinger.com
John Britt on sun 19 nov 06
It is probably explained in this article:
http://www.ceramicstoday.com/articles/flambe_magic.htm
Let me know,
John Britt
www.johnbrittpottery.com
William & Susan Schran User on sun 19 nov 06
On 11/18/06 4:05 PM, "Alyssa Ettinger" wrote:
> so my glazes are developing gritty particles that look like sand.
> glazes made a year ago, 6 months ago... doesn't matter. grit.
>
> glaze is:
> EPK - 15.0
> Fusion frit 38 - 33.0
> Whiting - 13.5
> feldspar - 13.0
> Silica - 25.5
Hmmm....Discovered sometime back that Ferro Frit 3110 is slightly soluble
and if stored wet it will develop the little granules.
Also had Dal Tile frit #439 that we discovered was very soluble, developed
so much grit, we had to throw the whole mixed glaze batch out.
Check with Fusion to see if frit #38 is at all soluble.
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Michael Wendt on sun 19 nov 06
Alyssa,
Pick one of the glazes that forms the grit.
When you screen it out, have it analyzed.
Google chemical analysis.
Check for prices since some charge
more than others.
My guess?
you are seeing a concretion process
because of the composition of
the glaze.
My saturated iron red gets these.
We don't throw them away but
ball mill them back in because
screening out concretions seems to
cause the glaze to change color.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, Idaho 83501
USA
wendtpot@lewiston.com
www.wendtpottery.com
Ron Roy on sun 19 nov 06
Hi Alyssa,
Could be crystals forming in your glaze bucket - are those glazes in a cool
place?
I can't see from the recipe what would be soluble enough to make that
happen though.
Try taking some glaze - with grit in it and heating to see if the "grit"
disolves - if so keep the glazes in a warmer place.
RR
>grrrrrrrr. so my glazes are developing gritty particles that look like sand.
>glazes made a year ago, 6 months ago... doesn't matter. grit.
>
>glaze is:
>EPK - 15.0
>Fusion frit 38 - 33.0
>Whiting - 13.5
>feldspar - 13.0
>Silica - 25.5 (i actually have upped this because of crazing)
>
>plus, i use masons for colorants: from 1-4%.
>
>there doesn't seem to be any correlation between what has more grit vs. what
>has more masons. at it seems random as to why some have more than others.
>
>obv, i've sieved them and will do so again if more form. but what are they?
>will more come?
>
>
>
>alyssa
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Lynne Antone on sun 19 nov 06
Alyssa,
Years ago I had a problem with one glaze forming beautiful six-sided crystals on the surface of the glaze in the bucket. I sieved the top of the glaze every time and heated the crystals til they melted, poured them back into the glaze and mixed it all up. A month later, it was the same problem. I was told it was probably the lithium carbonate causing the problem. Then another suggestion was to place an aquarium heater into the glaze as my studio was not heated at the time. This solved the problem, but I eventually got rid of the glaze.
So, if nothing else works, the aquarium heater does a good job. I got mine in the pet section of a Fred Meyer store. If you want to check the archives for the responses on my question, I believe most of the answers contained the subject "Glaze Crystals" in 1999.
Good Luck,
Lynne Antone
--
"Whenever I feel blue, I just start breathing again"
Beaver Creek Arts
Olympia WA
USA
-------------- Original message ----------------------
From: Alyssa Ettinger
> grrrrrrrr. so my glazes are developing gritty particles that look like sand.
> glazes made a year ago, 6 months ago... doesn't matter. grit.
>
> glaze is:
> EPK - 15.0
> Fusion frit 38 - 33.0
> Whiting - 13.5
> feldspar - 13.0
> Silica - 25.5 (i actually have upped this because of crazing)
>
> plus, i use masons for colorants: from 1-4%.
>
> there doesn't seem to be any correlation between what has more grit vs. what
> has more masons. at it seems random as to why some have more than others.
>
> obv, i've sieved them and will do so again if more form. but what are they?
> will more come?
>
>
>
> alyssa
> www.alyssaettinger.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.
Alyssa Ettinger on sun 19 nov 06
glazes are in buckets in a heated studio... so i guess next time i find
crystals and sieve i'll try to melt them.
alyssa
www.alyssaettinger.com
Alyssa Ettinger on mon 20 nov 06
and another PS: before i seived them out a couple got onto a pot i fired (i
thought i wiped them all off, but didn't)... and they fired just like little
pieces of sand, brown or white. ergo, they didn't melt.
a conundrum.
alyssa
www.alyssaettinger.com
| |
|
