Steve Slatin on tue 28 feb 06
bases, cone 6, oxidation
Alisa --
One more BIG thanks for the excellent
work you've done here. I can really
follow your process and your results
even without seeing pictures or holding
the finished work.
I haven't found pink fuming from
cobalt overglazes in the presence
of zinc (though I've only done it
once or twice) but I have seen a
hint of it in a partial-zinc glaze
that has cobalt as a colorant.
Of course, unless you have a 'bright
line' separation of cobalt from everything
else, any glaze with cobalt tends to
show the blue in preference to
everything else, but the hint of
pink has shown up several times,
making me think it's not flashing
from something else in my kiln.
Again, thanks, I really admire your
work and I'm just sorry you won't be
at NCECA because it'd be great to
meet you.
Best wishes -- Steve Slatin
--- Alisa Liskin Clausen
wrote:
> Glaze test for opacity and color response in 5
> transparent bases, cone 6,
> oxidation.
>
>
>
> Glaze are tested on white midrange stoneware
> fired in electric oxidation to
> 1220c. (2228f)
>
> Firing ramp with an electric controller is:
> 100c p/h to 600c (212f - 1112f)
> 150c p/h to 1140c (302f - 2084f)
> 80c p/h to 1220c (176f - 2228f)
> 15 min. soak
> cool down max. to 900c (1652f)
> Hold 1 hour
> Shut off kiln
>
> Note: All raw materials are measured up or down
> to the nearest half decimal.
>
> Colorants or additives to a 100 gram test batch
> are measured in percent to
> the 100 gram test batch.
>
> Frit 3134 has been substituted for a local high
> Boron Frit in side by side
> testing with no visible differences.
>
>
>
> The opacifiers used are Tin Oxide, Zink Oxide,
> Titanium Oxide, Zircopax and
> combinations of these.
>
>
>
> Tin tended to give a creamy white opacity.
>
> Zircopax gives a harder, sharper white, like
> bathroom porcelain.
>
> Zinc mostly did not opacify the clear bases but
> acted as a flux and shined
> up the bases.
>
> Titanium Dioxide gave the most interesting
> color response to the painted
> oxides, without much opacity.
>
> In all of the tests where the glaze contained
> Zinc, the stripe of Cobalt
> blue under glazed noticeably fumed pink. This
> validates again, the earlier
> tests I made, demonstrating fuming by under
> glazes in glazes containing Tin.
>
>
>
>
> Titanium produced green from Cobalt Oxide.
>
>
>
> Below is a list of the bases tested and the
> results of each added opacifier.
>
>
>
>
> 1.
>
> 20 x 5 Clear Base, by Tony Hansen, ^6,
> oxidation.
>
> 20 Frit 3134
>
> 20 EPK
>
> 20 Silica
>
> 20 Custer Spar
>
> 20 Wollastonite
>
>
>
> Base, transparent, gloss. Oxides showed true
> to color.
>
> 10 Zinc, transparent gloss, oxides showed true
> to color.
>
> 10 Zircopax, bright white gloss, Cobalt strong
> blue, under glaze grayish,
> RIO is covered and shows grayish.
>
> 10 Tin, softer white gloss, Cobalt is strong,
> under glaze is lighter blue
> and iron is visible but grayish.
>
> 5 Titanium, transparent gloss, slightly creamy
> color, cobalt strong, under
> glaze clear, RIO brown and clear. Not much
> opacity.
>
> 5 Tin, 5 Zircopax, bright white gloss, cobalt
> is broken and mottled, under
> glaze almost lost and iron is covered.
>
> 10 Titanium, white gloss, Cobalt is even more
> broken and pebbly, under glaze
> and RIO are mostly covered.
>
> 5 Tin, creamy white gloss, Cobalt is strong,
> under glaze is a light blue,
> RIO is grayish to covered.
>
>
>
>
>
> 2.
>
> Alisa's Dolita Clear, Silk Mat, cone 6
> oxidation. (named for Dolomite and
> for a person I like as much as this glaze)
>
> 27 Frit 3134
>
> 30 EPK
>
> 18 Silica
>
> 10 Ball Clay
>
> 15 Dolomite
>
>
>
> Base, transparent, silk mat, Cobalt is true,
> under glaze is slightly muted,
> and RIO is brown.
>
> 10 Zinc, shinier white semi gloss, Cobalt is
> true, under glaze is slightly
> bluer than above and RIO is brown, no opacifty.
>
> 10 Zircopax, bright white semi mat, Cobalt
> true, under glaze slightly greyer
> and paler and RIO is covered.
>
> 10 Tin, Toast colored semi gloss, both blues
> are grey and RIO is brown.
>
> 5 Titanium, grey blue silk mat, slightly white
> crystals, Cobalt is muted,
> under glaze is green with yellow specs and RIO
> is slightly covered.
>
> 5 Titanium, 5 Zircopax, silk mat, medium white
> with toast color edges.
> Cobalt is muted, under glaze is muted and RIO
> is visible and brown.
>
> 5 Tin, cream white silk mat, Cobalt is true,
> under glaze is slightly muted
> and RIO is true and brown.
>
> 10 Titanium, grey blue and yellow glaze, Cobalt
> is blue and green, under
> glaze is green with yellow specs, iron is
> visible with yellow specs.
>
>
>
> 3.
>
> Mike Bailey's Shiny Clear, ^6 oxidation.
>
> 43 Soda Spar
>
> 5 China clay
>
> 2 Bentonite
>
> 22.5 Whiting
>
> 6 Zinc Oxide
>
> 21.5 Silica
>
>
>
> Base, transparent, gloss. Oxides and under
> glaze showed true.
>
> 10 Zinc, no noticeable difference from base
>
> 10 Zircopax, bright white gloss, Cobalt shows
> through
=== message truncated ===
Steve Slatin --
In watermelon sugar the deeds were done and done again
as my life is done in watermelon sugar.
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Steve Slatin on thu 2 mar 06
bases, cone 6, oxidation
Alisa --
Yes, I saw your second message after
sending mine ... just one of those
e-mail things.
Your tests are way, way beyond mine
(I'm still doing rutile! Just did
some more comparing sieved with
unsieved mixes ...) and I don't have
any ideas about those little pink
crystals; I just recently started
working with a glaze that gets a
bit of that effect. Curiously, it
has both zinc and tin, so I have no
idea yet what's causing what. I
guess I could make up two batches,
one with tin and one without and see
which does what ... there's always
more to learn.
Best wishes -- Steve S
--- Alisa Liskin Clausen
wrote:
> Hi Steven
> I sent a correction to this mistake in the
> paragraph, where I wrote Zinc,
> and as the last sentenced shows, meant Tin.
> But that is not as apparent
> as I thought, because it is easily misread that
> now I have had fuming with
> under glazes with both Zinc and Tin. Fact is,
> I have had fuming with all
> of bases with Tin where the under glaze is
> applied.
>
> What about those bright pink crystals in the
> Cobalt wash over the bases
> with Zircopax? Do you have any ideas about
> those? They are very pretty
> but I am not sure I will always want them.
Steve Slatin --
In watermelon sugar the deeds were done and done again
as my life is done in watermelon sugar.
__________________________________________________
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May Luk on fri 3 mar 06
Hello Alisa and friends;
I'm not clear on the tin or zinc confusion. Can you
post the recipe (*gulp*) on that pink speck one? I
have done some currie grid in a high magnesium glaze.
Our glaze group was looking for pink specks cobalt
matte glaze. We find that, as usual, the Si:Al ratio
is important, as well as the cooling rate. Slow
cooling gives bigger specks. Here's a photo and the
recipe and explanation. I have all the calculation
figures if anybody is interested. It's Mike Bailey
glaze, so the 'corner C' analysis is easy to look up.
Please scroll down, the glaze test and info and on the
left column
http://www.londonpotters.com/files.asp
I have also done one David Hewitt high magnesium
(MCM2, Cone 6 Glaze Book) with Titanium and cobalt.
Nice teal colour with gold specks. It appears to be
like yours, more or less. I just remember; RR said
it's too dry for his taste.
Alisa, you probably have your glaze testing system. I
find it if I have doubts, I run the glaze base test
with a currie grid. So much happens in that grid. I'm
doing Mike Bailey style grid test; ie: currie grid but
on 49 upright tiles. The diping method gives me truer
results because I don't brush my glaze. The Oriental
Glaze book by MB explans it very well. So, that's my
2p's worth about glaze test. Hope you don't mind me
saying that.
Best Wishes
May
London UK
P.S. Thanks for your input on the glaze posting
matter. Don't want to say too much. I'm just exhausted
and vexed, like most slayarter perhaps. hehe. I just
want to get on with it. At the end of the day,
everybody will do what they wish based on their
ideology. I'm positively encouraged by some eccentric
behaviours of fellow clayarters though.
Alisa Liskin Clausen on sat 4 mar 06
On Fri, 3 Mar 2006 22:56:22 +0000, May Luk
wrote:
>Hello Alisa and friends;
>
>I'm not clear on the tin or zinc confusion. Can you
>post the recipe (*gulp*) on that pink speck one?
Hi May!
The tin and zinc confusion was because I wrote this
all of the tests where the glaze contained Zinc, the stripe of Cobalt blue
under glazed noticeably fumed pink. This validates again, the earlier
tests I made, demonstrating fuming by under glazes in glazes containing
Tin.
I meant to write ...where the glaze contained TIN, stripe of Cobalt
blue...etc.
However, the pinks specs in the Cobalt was another issue.
In tests where Zircopax was used to opacify the bases Tony Hansen=92s 20 x
5, Alisa=92s Dolita Clear and Mike Bailey=92s Shiny Clear,
pink crystals formed on the Cobalt Oxide wash.
The recipes are with added 10% Zircopax:
20 x 5 Clear Base, by Tony Hansen, ^6, oxidation.
20 Frit 3134
20 EPK
20 Silica
20 Custer Spar
20 Wollastonite
2.
Alisa=92s Dolita Clear, Silk Mat, cone 6 oxidation. (named for Dolomite and=
for a person I like as much as this glaze)
27 Frit 3134
30 EPK
18 Silica
10 Ball Clay
15 Dolomite
Mike Bailey=92s Shiny Clear, ^6 oxidation.
43 Soda Spar
5 China clay
2 Bentonite
22.5 Whiting
6 Zinc Oxide
21.5 Silica
From what Steve and Ivor are saying, I think I have to see what additional
firings yield. I am sorry to say that I already will feel disappointed if
no pink crystals appear!. They are very pretty for Peptal Bismal pink!
I certainly like to hear how you are testing May. I like Ian's Grid and I
am just looking more at Hewitt's site, at triaxle blends. I would like to
do this tile method because I like to see more of the glaze than I get on
the grid. I am sure I can combine these methods to get a good look at the
glazes I select to test further. I think your comments are always
interesting and hope you keep us informed on what you are doing.
Regards from Alisa in Denmark
May Luk on sun 5 mar 06
Hi Alisa;
Yours are very similar to Bill E's stormy lavendar
blue, but less stormy?
I put your recipes into Glaze Master and I have a
rough calculation for my own comparing purposes. I'm a
bit slow, so I need to put the recipes in context and
think out loud. Please allow me to indulge.
I checked out zicopax is 0.22 CaO and 34.28 SiO2 in
unity. Your three glazes are not all of the same
class- quite a bit of variables amongst them. If all
of them gives you pink specks, zinc is not the only
contributing factor because only Mike B Shiny Clear
contains zinc. Maybe they are different kind of pink
specks. I know that in high magnesium cobalt matte
glaze with the right Si:Al ratio and controlled cool
gives out pink specks. In our glaze tests, we have
obtained pink pyroxene (CaO.MgO.2Si02). If that's what
you got and/or after, then the glazes seem to have the
right components.
This is definitely the time for quadrxial blend and
families of the same base glaze. If you want to see if
zinc does anything. Do one set with zinc and one set
without. One variable at a time. I'm only so certain
because I have done it and I got my results (together
with my glaze group, we all got what we needed from
the grids - well, as another stepping point, really)
But first you have to decide what other qualities you
need from this glaze, then you can pick one out of the
three to be your corner C base glaze and go from
there. The thinking and planning takes one hour. Doing
the test takes half day. Oh so easy if your have all
the testing paraphernalia. :-))))
I'll wait for your photos before I take up anymore
bandwidth. I'd like to compare them with mine.
Let's keep 'talking'
Regards
May
(I hope the chart line up!)
__________20 X 5____ __Alisa's Dolita______MB Shiny
Clear
Na20_____0.148_______0.148____________0.138
K2O______0.075_______0.011____________0.039
MgO______0.027_______0.255____________0.005
CaO______0.751________0.588___________0.623
ZnO__________0____________0____________0.196
Al2O3____0.372________0.422___________0.258
B2O3_____0.223________0.288___________0
Fe2O3____0.005________0.007___________0.002
SiO2______3.693________2.94____________2.512
Si:Al_______9.92_________6.97____________9.75
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