GORMO1@AOL.COM on sat 26 aug 00
Floating blue blisters! People can say what they what but 95%
comes from to thick of glaze application period. I have used it in
a classroom for over 15 years and proven it many times. For people
who glaze a pot w/fb a then puts it right into the kiln to fire and it
crawls its not the glaze it you rushing the glaze !Which in most cases
is not the glaze or the kiln its the person doing it. That goes for all
glazes ! I know I have been their!
GORMO I POTTERY
POTTER : JIM GORMAN
500 SOUTHGATE DRIVE
BLACKSBURG,VA 24060
PHONE 540-953-0673
E-MAIL GORMO1@AOL.COM
Autumn Downey on sat 26 aug 00
Hi all,
I know floating blue has been talked through a number of times, but I
haven't been able to find anyones explanation as to why it sometimes blisters.
At our Guild that we have to fire FL blue at cone 5 anyway, cone 6 is
greenish and often blistered.
A number of mugs, fired at the top (which is the cool spot and usually a
good place) (envirovent's at bottom) have huge crater-like blisters. When
I first rubbed my hand over these there were little static pops! One other
piece had no flaws at all. It was a little larger and thicker than the
mugs and glazed only in Fl blue and had turned a little greenish. (Maybe
held the heat better and surface settled out - though another piece of
similar proportions, double dipped in a yellow glaze had blisters in its fl
blue area.) Confusing! All were on the same shelf, though there could
have been cooler spots away from the hinge side of the lid, plus those
little holes for ventilation...
Most of the blistered pieces were also partly dipped in Randy's red -
however it was the pure Fl Blue area that blistered. It was also very blue
- and looked as though colours were still swirling about and the GB
spluttering when it froze.
Fl Blue does have alot of alumina - is that perhaps why it's viscous and
sometimes doesn't smooth over - in spite of being very glossy and melting
quite well?
We use the original recipe from Chappell. I believe there are others that
are improvements on this glaze. I will seek them out, but first wanted to
try to understand why this one is so darned fickle - as is often said about
it.
Anyway, for reference, here's the glaze again. Thank you.
Autumn Downey.
Floating Blue
=============
NEPHELINE SYENITE... 2365.00 44.21%
gerstley borate..... 1350.00 25.23%
FLINT............... 1015.00 18.97%
EPK KAOLIN.......... 270.00 5.05%
IRON OXIDE RED...... 100.00 1.87%
cobalt oxide........ 50.00 0.93%
rutile.............. 200.00 3.74%
========
5350.00
CoO 0.05* 1.03%
CaO 0.39* 6.19%
MgO 0.10* 1.18%
K2O 0.10* 2.75%
Na2O 0.36* 6.36%
TiO2 0.18 4.07%
ZrO2 0.00 0.04%
Al2O3 0.48 13.99%
B2O3 0.39 7.69%
P2O5 0.00 0.01%
SiO2 3.19 54.49%
Fe2O3 0.05 2.21%
Cost/kg 3.55
Si:Al 6.61
SiB:Al 7.42
Expan 8.36
Notes:
A finicky glaze; pinholes or sometimes blisters. Must not be
contaminated.
Apply thickness of a dime. Do not overfire.
Jonathan Kaplan on sat 26 aug 00
Well we have been through this any number of times both on the list and off.....
The combinations of gerstly, iron, and rutile are problematic both electic
and gas kilns. Your glaze forms these blisters, or zits, or exagerated pin
holes because of the interations of these materials as they out gas and
don't heal over. It could also be the clay, but not likely. Reducation
adversely effects these glazes also.
You could alter your firing schedule to include a healthy soak at the end
of the firing to try and heal over these problem areas. You could fire to
to a more accurate maturing point of the glaze. Or you could try Ron Roy's
alteration to floating blue.
But what I would suggst is that you banish this glaze from your studio.
Permanently. It will be an endless source of frustration for you time and
time again. Trust me, I know these glazes quite intimately. Even though the
color and the surface make the ware sellable and you just love the color
and surface, it will break your heart many times over. You work too hard to
through your wares away.
Now I know that there are potters out there using formulas similar to this
and it works and that's fine. If you can get it to work consistantly, power
to you.
You could go to http://digitalfire.com/education/glaze/floating-blue.html
and find my piece on the trials and tribulations of "floating blue" and the
like for an analysis of how we deal with glazes such as this.
I still have trouble understanding why potter's butt heads with this
formula and just don't drop it from their group of glazes and move one!
Best
Jonathan
Jonathan Kaplan
Ceramic Design Group LTd/Production Services
PO Box 775112
Steamboat Springs, CO 80477
(970) 879-9139 voice and fax
http://www.sni.net/ceramicdesign
UPS: 1280 13th St. Unit13
Steamboat Springs, CO 80487
patrick conrey on sun 27 aug 00
>.
AMEN! I have been through hell trying to get a "Few" good pieces from a
kiln load. At one point I pulled the trash bin up to the kiln to
eficiently unload!!!!
Diane G. Echlin on sun 27 aug 00
I have to agree with Jim's assessment here. the only place I ever get blisters
with FB is in creases and corners of my work, and now that he mentions it, I will
certainly be more careful with my application! I've also found that a single,
longer dip is better than two quick dips, as the glaze seems to hold onto the
bisque better. Important, though, to let it dry thoroughly before firing it up.
Diane in CT
GORMO1@AOL.COM wrote:
> Floating blue blisters! People can say what they what but 95%
> comes from to thick of glaze application period. I have used it in
> a classroom for over 15 years and proven it many times. For people
> who glaze a pot w/fb a then puts it right into the kiln to fire and it
> crawls its not the glaze it you rushing the glaze !Which in most cases
> is not the glaze or the kiln its the person doing it. That goes for all
> glazes ! I know I have been their!
>
> GORMO I POTTERY
> POTTER : JIM GORMAN
> 500 SOUTHGATE DRIVE
> BLACKSBURG,VA 24060
> PHONE 540-953-0673
> E-MAIL GORMO1@AOL.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.
Tom Wirt/Betsy Price on wed 30 aug 00
Subject: Re: Floating blue blisters
> >I know floating blue has been talked through a number of times, but
I
> >haven't been able to find anyone's explanation as to why it
sometimes blisters.
> >
> >A number of mugs, fired at the top (which is the cool spot and
usually a
> >good place) (envirovent's at bottom) have huge crater-like
blisters. When
> >I first rubbed my hand over these there were little static pops!
One other
> >piece had no flaws at all.
>though another piece of
> >similar proportions, double dipped in a yellow glaze had blisters
in its fl
> >blue area.) Confusing! All were on the same shelf, though there
could
> >have been cooler spots away from the hinge side of the lid, plus
those
> >little holes for ventilation...
>
Hi Autumn..
Welcome to floating blue. We use it at cone 10, based originally on
Conrad's Moonlight Blue, now using an adaptation worked out by the
venerable Wizard of Ooze from the North (well, east of here).
All the flaws you describe are part of working with Floating Blue.
Plus crawling. Besides the possible causes you describe, we suspect
that part of the problem comes from the Rutile (which is a variable
raw titanium ore) and may have stuff boiling off along with any
gerstley. As has been discussed here before, this stuff is just pain
touchy....thickness of the glaze in the bucket, application thickness,
firing cycle, cooling cycle.
It's probably a glaze that's right on the edge and as such, there is
no tolerance for much variation in all the various steps of glazing.
We even had the experience of sending our recipe to David Hendley who
uses a Rutile blue regularly and he got baby poop brown. He sent us
his recipe, and we got baby poop brown.
Thickness in the bucket...do NOT use Epsom salts with this glaze! Use
Darvan 7 to defloculate it so you have as little water as possible in
the bucket. Pay strict attention to your specific gravity measured as
recently described by Jonathan Kaplan by volume/weight. We use a
double dip application, letting the first coat just start to lose it's
sheen before the second quick dip. Jim Gorman is correct in the
thickness of application notes. Look at your glaze under a magnifier
after it dries. If it's got tiny cracks (the pinholes don't matter),
it will crawl and it comes from either too much water in the bucket,
or too much clay in the recipe or too thick an application. It must
be dry before it goes in the kiln.
It is very touchy to kiln placement as you've discovered. And a bit
slower at the end may help the pinholes seal before cooling. Our
recipe does not like to be over some glazes...it crawls or pinholes.
My suspicion is that if it starts to melt earlier than the under
glaze, it has no bond to the body and just slides off.
It took us over 3 years of working daily with this Rutile blue before
it was consistently good....and then about the time you think you've
got it, off it goes.
When it does go bad, we can sometimes salvage the piece by applying a
dab of glaze to the pinholes and maybe a thin coat overall and
refiring...although the final look is more watery with less blue
(although more floating as you described).
About all I can really suggest is to keep at it. Get rid of all the
nasty ingredients as Ron suggested and keep meticulous notes of your
processes and materials. If nothing else, you'll learn a lot about
glazes in general.
Moonlight Blue Cone 10
Adaptation from Conrad
With Ron Roy's Help
Cornwall Stone 27
G200 Spar 15.5
Gerstley 1999 4.0
Frit 3134 13
Dolomite 2
Silica 12
Whiting 6.50
OM4 Ball 18.99
Rutile 3.0
Illmenite pwdrd 2.0
Cobalt Carb 3/10
Conrad G375-the original
Moonlight Blue Cone 9-10
Cornwall Stone 63.8
Gerstley Borate 14.3
Silica 7.6
Whiting 7.6
EPK 4.8
Zinc Oxide 1.9
Rutile Powdered 3.2
Ilmenite 2.0
Cobalt Carbonate 3/10's %
Ron's Coyote Blue #2
Not really tested yet....removes all gerstley
CORNWALL STONE 27
G-200 FELDSPAR G200 16
FRIT 3134 18
DOLOMITE 4
SILICA 18.5
WHITING 6
OM #4 BALL CLAY 9
EPK KAOLIN 8
RUTILE 3
Cobalt Carb 3/10's %
Illmenite Powdered 2
Oh yes, as you said you'd do, there is a lot in the archives....at
least one major discussion every year for the last 5 or 6.
Good Luck
Tom Wirt
Mary Lynch on wed 30 aug 00
To Autumn and others who are working with the infamous Floating Blue:
I just fired a test batch and wanted to share the info: a friend mixed up a
1000 gram sample using Gerstley Borate and sent it to me (it was the
standard formula). I have never used it and had only read the trials and
tribulations of others, so I was apprehansive, to say the least. I added
enough water so that I got 4 drips at 1-second intervals after the stream
running off the stirring stick turns to droplets.
I dipped the test pieces (small bowls and cylinders) and they sat overnight
before firing. I set my Skutt 1027KM for ^6, medium speed, with a 10 min.
soak at the end. The firing took 8 hrs. 36 min. Cones throughout kiln
indicated a full ^6 had been reached, though a bit hotter at the bottom than
the top (kiln was not packed tightly).
All the tests turned out beautifully! I used Highwater's P-5 porcelain body
and their ^6 Speckled brownstone - I preferred it on the darker clay.
Beginner's luck, perhaps . . . now to test Ron Roy's formulas minus the GB.
I'm also writing up other glaze tests and will post as well. I got tiny
blisters w/ static pops (as described so well by Autumn) on another glaze
that was too thickly applied and fired 1 cone over its limit.
Thanks to all Clayarters who take the time to give info and feedback so
generously - coming here is like going to the well for me. I hope to give
back a little, too, but it will never be as much as I get.
- Mary Lynch, who's feeling pretty lucky right now!
Ron Roy wrote:
> There are many factors to consider - properly fired bisque, application,
> speed of firing, soak period. Some potters use this glaze and get
> consistent results.
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