Lari Ward on wed 31 may 00
I have been firing with 80/20 for my raku crackle at 1850 for years and =
never had a problem. I just raku fired with 80/20 over terra sig and =
got bubbles at 1850. When cool I have pinholes that are carbonized, =
some big crackle and of course cooled flat bubbles. I fired to 1900 and =
still it didn't flatten out, actually it got worse. The next time I =
fired to 1700 and pulled the pieces and I have a fairly nice, matte =
crackle. So I fired to 1725 and at that temp it looks under fired, it =
is just beginning to form bubbles. Does any one have a clue what is =
going on and what I should fire these to, to get my shinny crackle? The =
Terra sig is made with OM-4 and the clay is Raku II from SPS. By the =
way, I have 26 plaques that need to be finished by this weekend and they =
are all glazed. :-( Thanks
Lari=20
In Poulsbo, WA where Spring feels like Fall. =20
Jeff & Melanie Boock on thu 1 jun 00
I am right there with you, trying to smooth out those bubbles in a
large bowl as I type. Really frustrating.
I hope someone can get to the bottom of this.
Jeff Boock
>I have been firing with 80/20 for my raku crackle at 1850 for years
>and never had a problem. I just raku fired with 80/20 over terra
>sig and got bubbles at 1850. When cool I have pinholes that are
>carbonized, some big crackle and of course cooled flat bubbles. I
>fired to 1900 and still it didn't flatten out, actually it got
>worse. The next time I fired to 1700 and pulled the pieces and I
>have a fairly nice, matte crackle. So I fired to 1725 and at that
>temp it looks under fired, it is just beginning to form bubbles.
>Does any one have a clue what is going on and what I should fire
>these to, to get my shinny crackle? The Terra sig is made with OM-4
>and the clay is Raku II from SPS. By the way, I have 26 plaques
>that need to be finished by this weekend and they are all glazed.
>:-( Thanks
>Lari
>In Poulsbo, WA where Spring feels like Fall.
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
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>melpots@pclink.com.
Sharon31 on fri 2 jun 00
Hi!
Just keep it longer in the kiln, untill the bubbles "settled down" and the
glaze will be shiny and clear.
Ababi
sharon@shoval.org.il
http://www.israelceramics.org/main.asp?what=gallery.htm
http://www.milkywayceramics.com/cgallery/asharon.htm
Lari Ward on sat 3 jun 00
This is a glaze with a personality problem that is defying treatment. At
1700 I can pull it and it looks like it is on the edge of melting, snowy,
kind of matte. At 1725 it is obviously beginning to bubble and it looks
totally underfired. At 1800 it looks slightly smooth, obvious bubbles. A
few less bubbles at 1850, but still not smooth. THEN it gets worse! Way
more bubbles. SO is it over fired, underfired or both. Since this is the
same bucket of glaze I have used for a while without problems, could the
terra sig be affecting it? Has anyone got a crackle glaze that doesn't use
G.B. in it?
Thanks
Lari
In western Washington, where today is summer and yesterday fall.
----- Original Message -----
From: "Diane G. Echlin"
To:
Sent: Saturday, June 03, 2000 5:33 AM
Subject: Re: HELP with Raku crackle
> It sounds to me like you are WAY over firing your work. When I raku, I
keep a
> close eye on the kiln as soon as it hits dull red, so I can monitor the
melt. (I
> don't use a pyrometer) I like to check every ten minutes or so after I
see the
> glaze has reached the really ugly/bubbly stage. from there I can watch
the
> progression of the glaze smoothing out. Hope this helps.
> Di
>
> Jeff & Melanie Boock wrote:
>
> > I have tried this, leaving the pot in the kiln at 1850 for an extra
> > hour, and the bubbles seemed to get worse, not better.
> >
> > Jeff
> >
> > >Hi!
> > >Just keep it longer in the kiln, untill the bubbles "settled down" and
the
> > >glaze will be shiny and clear.
> > >Ababi
> > >sharon@shoval.org.il
> > >http://www.israelceramics.org/main.asp?what=gallery.htm
> > >http://www.milkywayceramics.com/cgallery/asharon.htm
> > >
> >
>___________________________________________________________________________
___
> > >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.
> >
> >
____________________________________________________________________________
__
> > 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.
>
>
____________________________________________________________________________
__
> 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.
>
KYancey on sat 3 jun 00
Hello Jeff & Melanie Boock,
If the bubbles are getting worse, I would imagine that you are over-firing. I
usually get a good melt of the 80/20 glaze around cone 08. Since Gerstly Borate is
not consistant and at times have higher levels of impurities, I make sure my flue
is fully open (6 in diam) then reduce the pressure on my regulator a little bit
(starting, let's say, around 1600 F. ) until my temperature advance slows down
while I am approaching 1750 F.
As a side note: I tried this technique with 80% Murray's Borate and 20% Nephiline
Syenite and I ended up chipping every bit of it off my kiln shelves. I'll be
testing this again at a much lower temp.
Hope this helps Ken
Diane G. Echlin on sat 3 jun 00
It sounds to me like you are WAY over firing your work. When I raku, I keep a
close eye on the kiln as soon as it hits dull red, so I can monitor the melt. (I
don't use a pyrometer) I like to check every ten minutes or so after I see the
glaze has reached the really ugly/bubbly stage. from there I can watch the
progression of the glaze smoothing out. Hope this helps.
Di
Jeff & Melanie Boock wrote:
> I have tried this, leaving the pot in the kiln at 1850 for an extra
> hour, and the bubbles seemed to get worse, not better.
>
> Jeff
>
> >Hi!
> >Just keep it longer in the kiln, untill the bubbles "settled down" and the
> >glaze will be shiny and clear.
> >Ababi
> >sharon@shoval.org.il
> >http://www.israelceramics.org/main.asp?what=gallery.htm
> >http://www.milkywayceramics.com/cgallery/asharon.htm
> >
> >______________________________________________________________________________
> >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.
>
> ______________________________________________________________________________
> 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.
Diane G. Echlin on sun 4 jun 00
Lari,
How old is this bucket of glaze? As you alluded to at the end of your post, GB is
soluble in water to some extent. Perhaps your should mix up a small batch (100
grams) of new glaze, same recipe, and fire one piece with the new batch, and one
with the old, at the same time and see if there is a difference. I had been having
the same trouble as you, and tried this. I came to find out later that the old
bucket had been sitting around for well over a year, but my new batch worked fine.
Alternately, try Steve Branfman's basic white crackle recipe (it's a variation on
80/20) When applied thick enough it comes out like glass with really nice
crackle. Let me know if you need the recipe.
Di
Lari Ward wrote:
> This is a glaze with a personality problem that is defying treatment. At
> 1700 I can pull it and it looks like it is on the edge of melting, snowy,
> kind of matte. At 1725 it is obviously beginning to bubble and it looks
> totally underfired. At 1800 it looks slightly smooth, obvious bubbles. A
> few less bubbles at 1850, but still not smooth. THEN it gets worse! Way
> more bubbles. SO is it over fired, underfired or both. Since this is the
> same bucket of glaze I have used for a while without problems, could the
> terra sig be affecting it? Has anyone got a crackle glaze that doesn't use
> G.B. in it?
> Thanks
> Lari
> In western Washington, where today is summer and yesterday fall.
>
Sharon31 on mon 5 jun 00
Hello Lari!
My Raku glaze does not have G.B. but a German frit that is not available in
America.
With my small knowledge, I converted it to your materials. this glaze is
similar to the late 80/20. Perhaps, The glaze gurus can improve it. May be
by changing the Pearl Ash to an insolouble material.
My glaze(From my good adviser Yehuda Koren)
Raku 70/30
==========
FRIT 6004........... 70.00 70.00%
WOLLASTONITE........ 30.00 30.00%
========
100.00
CaO 0.51* 14.48%
K2O 0.23* 10.85%
Na2O 0.26* 8.05%
Al2O3 0.05 2.45%
B2O3 0.51 17.85%
SiO2 1.53 46.32%
Cost/kg 15.44 Israeli Shekel
Si:Al 32.10
SiB:Al 42.78
Expan 11.18
The Western version:
70/30west
=========
FRIT 3134........... 69.77 69.77%
PEARL ASH........... 17.19 17.19%
EPK KAOLIN.......... 5.89 5.89%
FLINT............... 7.16 7.16%
========
100.00
CaO 0.54* 15.60%
MgO 0.00* 0.01%
K2O 0.22* 10.72%
Na2O 0.24* 7.86%
TiO2 0.00 0.02%
Al2O3 0.05 2.43%
B2O3 0.49 17.61%
P2O5 0.00 0.02%
SiO2 1.46 45.68%
Fe2O3 0.00 0.05%
Cost/kg 32.81 Israeli Shekel
Si:Al 31.92
SiB:Al 42.54
Expan 11.21
Hope I brought the light to Amarica!
Ababi
sharon@shoval.org.il
http://www.israelceramics.org/main.asp?what=gallery.htm
http://www.milkywayceramics.com/cgallery/asharon.htm
Coolpots@AOL.COM on tue 6 jun 00
Jeff,
It sounds like you are overfiring your raku. It goes through a bubble stage
and then slicks out. That is when you should pull it. If you fire longer and
it bubbles again, it won't slick back out. Are you watching your pots from
the hole in top? After about 45 min. of firing, I start watching the pots
closely and pull after about 5 min. of gloss.
Raku is difficult to get just right and I am still working on it. Hope this
helps.
Vicki in Cool, CA
Jeff & Melanie Boock on mon 12 jun 00
I have tried this, leaving the pot in the kiln at 1850 for an extra
hour, and the bubbles seemed to get worse, not better.
Jeff
>Hi!
>Just keep it longer in the kiln, untill the bubbles "settled down" and the
>glaze will be shiny and clear.
>Ababi
>sharon@shoval.org.il
>http://www.israelceramics.org/main.asp?what=gallery.htm
>http://www.milkywayceramics.com/cgallery/asharon.htm
>
>______________________________________________________________________________
>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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