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titanium oxide effects.

updated tue 21 dec 99

 

Maurice Cain on fri 19 nov 99


Dear Clayarters;
I've researched the archives and hit the books including Hamer & Hamer
to no avail so I turn to the Glaze Gurus for help please.

In an attempt to get the perfect to die for Blue on Standard 112 clay I
have arrived at the following recipe thanks in no small part to RR
himself for the starting point.

Frit 3134 20 19.23
G200 FS 14 13.46
Wollastonite 14 13.46
Strontium 5 4.81
Talc 8 7.69
EPK 23 22.12
Silica 20 19.23

total 104 100%

This leads to a Unity formula (1.0 flux) (0.32 AL2O3) (0.19 B2O3)
(2.91 SiO2) which seems to be well within the limits for cone 6. 1.5%
cobalt oxide gives the blue I'm looking for.

Now here's the rub..... I've added 5% Titanium Oxide ( Dioxide?) and
have observed that the glaze now runs down the pot to form a thick roll
at the foot. What's happening here? Is the TiO2 acting as a fluxing
agent ( melter?) and do I have to add more EPK to stiffen it up again?
I'm aiming to get a lighter mottled blue.

TIA mo cain exPat Brit ATLGA.

Edouard Bastarache on sat 20 nov 99

------------------
Hi all,

according to Robin Hopper in The Ceramic Spectrum
titanium dioxide reacts as a refractory material.
According to Andr=E9anne Vachon, a chemist working
for Tioxide of Canada, this stuff melts between 1800-1840 C

Later,

Edouard Bastarache
edouardb=40sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/=7Eedouardb/
-----Message d'origine-----
De : Maurice Cain =3Cmocain=40bellsouth.net=3E
=C0 : CLAYART=40LSV.UKY.EDU =3CCLAYART=40LSV.UKY.EDU=3E
Date : 19 novembre, 1999 11:55
Objet : Titanium Oxide effects.


=3E----------------------------Original message----------------------------
=3E
=3EDear Clayarters=3B
=3EI've researched the archives and hit the books including Hamer =26 Hamer
=3Eto no avail so I turn to the Glaze Gurus for help please.
=3E
=3EIn an attempt to get the perfect to die for Blue on Standard 112 clay I
=3Ehave arrived at the following recipe thanks in no small part to RR
=3Ehimself for the starting point.
=3E
=3E Frit 3134 20 19.23
=3E G200 FS 14 13.46
=3E Wollastonite 14 13.46
=3E Strontium 5 4.81
=3E Talc 8 7.69
=3E EPK 23 22.12
=3E Silica 20 19.23
=3E
=3E total 104 100=25
=3E
=3EThis leads to a Unity formula (1.0 flux) (0.32 AL2O3) (0.19 B2O3)
=3E(2.91 SiO2) which seems to be well within the limits for cone 6. 1.5=25
=3Ecobalt oxide gives the blue I'm looking for.
=3E
=3ENow here's the rub..... I've added 5=25 Titanium Oxide ( Dioxide?) and
=3Ehave observed that the glaze now runs down the pot to form a thick roll
=3Eat the foot. What's happening here? Is the TiO2 acting as a fluxing
=3Eagent ( melter?) and do I have to add more EPK to stiffen it up again?
=3EI'm aiming to get a lighter mottled blue.
=3E
=3ETIA mo cain exPat Brit ATLGA.

Thonas C. Curran on sat 20 nov 99

Maurice...standard clay 112 is cone 4 to 6, but how about your glaze?
Oxidation, cone? TIA Carolyn

Michael Banks on sun 21 nov 99

Maurice Cain wrote: (snip)
> Now here's the rub..... I've added 5% Titanium Oxide ( Dioxide?) and
> have observed that the glaze now runs down the pot to form a thick roll
> at the foot. What's happening here? Is the TiO2 acting as a fluxing
> agent ( melter?) and do I have to add more EPK to stiffen it up again?
> I'm aiming to get a lighter mottled blue.

I've read that TiO2 is meant to stiffen glazes but have found the opposite.
I tried using it as substitute for alumina (to get away from the dulling
effect on colour that alumina has) after reading that titanium increased
viscosity in Hamer. But with the glazes I was trialling (high in boric
oxide and zinc), white TiO2 had no stiffening effect and led to increased
fluidity.

In nature, titanium-rich magmas can be quite fluid. Hawaiian basalt contains
up 3 or 4% TiO2 and is some of the runniest lava around. Most of the Period
4 transition elements (including Ti, Cu, Co, Mn etc,) appear to fluidise
silicate melts and must disrupt the formation of the network bonds which is
a cause of viscosity.

Titanium doesn't act too refractory in my experience either, despite the
high melting point of the pure oxide. The melting points of oxides are a
poor guide to melting behaviour in complex silicate melts and TiO2 must have
low eutectics with alkalis and other fluxes. The mineral sphene (CaTiSiO5)
is 40% TiO2 and melts at ~cone 5, similar to potash feldspar.

Michael Banks,
Nelson,
New Zealand

Khaimraj Seepersad on mon 22 nov 99

Good Day , to All ,
Hello Michael Banks,

I hesitated to say anything on Tio2 , as I figured Michael would do his
very thorough response on unusual oxides etc. in Geology , Pottery
and anything else .
I am not an expert , nor trained in glaze science , just an amateur
muckabout working in lowfire frit and enamels - home-made .

Titanium Dioxide although a refractory , gives greater fusibilty than
silica . It's surface tension is 3.00 x 10 -3 [ j/m2 { at 900 deg.c ]
silica is 3.40 x 10-3 [ J/m2 { at 900 deg.c ]
Ti02 in the enamel gives greater mobility .

Easily goes into solution in Boric Oxide , and Alkalis , forming low
Eutectics at 985 deg.c Na2Ti05
806 deg.c K2Ti03
to name a few - I made the Sodium Titanate and got a pale brown
glass type substance , very fluid when molten at 1050 deg.c .

In combination with Al203 , 2% + Ti02 , will usually fall out of solution
in a pottery glaze upon cooling
However when made into a frit high in Alkali and or Boric Oxide ,
Ti02 will remain in solution and be clear .

Used in an enamel or low fire pottery glaze frit , leaving out the Al203
will allow for Ti02's use in place of Al203 . However at high
Stoneware Temperatures you may need over 15 % Ti02, and add as
a frit [ natural or manmade ] to obtain a clear glaze with any viscosity .
You could probably use the Ti02 in the place of Alkali or Alkaline or
Boric Oxide [ or use less of each or all ].

Your glaze will exhibit ultra high gloss . This is what happens when I
make a lowfire clear glaze using Ti02 in place of Al203 .
Ti02 has a refractive index of approximately 2.55 +
The glaze also begins to feel like plastic or the surface of the metal
Titanium . Run a fingernail over the surface - quite pleasant .

Lastly , thank you for the information on Zirconium Oxide , very
educational .

Now can anyone say if a porcelain enamel , say for sheet steel is as
durable , chemically or physically as a stoneware or porcelain glaze ?
Khaimraj Seepersad



-----Original Message-----
From: Michael Banks
To: CLAYART@LSV.UKY.EDU
Date: 21 November 1999 13:36
Subject: Titanium Oxide effects.


>----------------------------Original message----------------------------
>Maurice Cain wrote: (snip)
>> Now here's the rub..... I've added 5% Titanium Oxide ( Dioxide?) and
>> have observed that the glaze now runs down the pot to form a thick roll
>> at the foot. What's happening here? Is the TiO2 acting as a fluxing
>> agent ( melter?) and do I have to add more EPK to stiffen it up again?
>> I'm aiming to get a lighter mottled blue.
>
>I've read that TiO2 is meant to stiffen glazes but have found the opposite.
>I tried using it as substitute for alumina (to get away from the dulling
>effect on colour that alumina has) after reading that titanium increased
>viscosity in Hamer. But with the glazes I was trialling (high in boric
>oxide and zinc), white TiO2 had no stiffening effect and led to increased
>fluidity.
>
>In nature, titanium-rich magmas can be quite fluid. Hawaiian basalt
contains
>up 3 or 4% TiO2 and is some of the runniest lava around. Most of the
Period
>4 transition elements (including Ti, Cu, Co, Mn etc,) appear to fluidise
>silicate melts and must disrupt the formation of the network bonds which is
>a cause of viscosity.
>
>Titanium doesn't act too refractory in my experience either, despite the
>high melting point of the pure oxide. The melting points of oxides are a
>poor guide to melting behaviour in complex silicate melts and TiO2 must
have
>low eutectics with alkalis and other fluxes. The mineral sphene (CaTiSiO5)
>is 40% TiO2 and melts at ~cone 5, similar to potash feldspar.
>
>Michael Banks,
>Nelson,
>New Zealand
>

David Hewitt on mon 22 nov 99

Maurice,
>From some recent tests with adding Titanium dioxide to a cone 8 glazes I
am surprised at hearing of the problem you have experienced.
I cannot, therefore, offer any specific advise, but in looking at your
glaze analysis and comparing it with one of my cone 6 base glazes, which
is a clear transparent shiny glaze, I would see that adding more EPK
would possibly be beneficial in any case. I would try increasing the
amount to 40 parts.
David

In message , Maurice Cain writes
>----------------------------Original message----------------------------
>
>Dear Clayarters;
>I've researched the archives and hit the books including Hamer & Hamer
>to no avail so I turn to the Glaze Gurus for help please.
>
>In an attempt to get the perfect to die for Blue on Standard 112 clay I
>have arrived at the following recipe thanks in no small part to RR
>himself for the starting point.
>
> Frit 3134 20 19.23
> G200 FS 14 13.46
> Wollastonite 14 13.46
> Strontium 5 4.81
> Talc 8 7.69
> EPK 23 22.12
> Silica 20 19.23
>
> total 104 100%
>
>This leads to a Unity formula (1.0 flux) (0.32 AL2O3) (0.19 B2O3)
>(2.91 SiO2) which seems to be well within the limits for cone 6. 1.5%
>cobalt oxide gives the blue I'm looking for.
>
>Now here's the rub..... I've added 5% Titanium Oxide ( Dioxide?) and
>have observed that the glaze now runs down the pot to form a thick roll
>at the foot. What's happening here? Is the TiO2 acting as a fluxing
>agent ( melter?) and do I have to add more EPK to stiffen it up again?
>I'm aiming to get a lighter mottled blue.
>
>TIA mo cain exPat Brit ATLGA.
>

--
David Hewitt

Michael Banks on tue 23 nov 99

Thanks for all this stuff Khaimraj, it confirmed my empirical testing.
Hey, we caught out the Hamers here. They regard TiO2 mainly as an opacifier
and not the more active material it is. Makes one question the line between
"flux" and "refractory"...

Apparently, the reason it pops out of solution in high alumina glazes (and
high zinc glazes too BTW) on cooling, is titaniums high crystal field
energy. This is the reason that it promotes macrocrystal development in Zn
glazes and devitrification in others.

Thanks again, its great to get hard data confirmation of pure observations.

Michael
in NZ

Khaimraj Seepersad wrote (snip)


> Titanium Dioxide although a refractory , gives greater fusibilty than
> silica . It's surface tension is 3.00 x 10 -3 [ j/m2 { at 900 deg.c ]
> silica is 3.40 x 10-3 [ J/m2 { at 900 deg.c ]
> Ti02 in the enamel gives greater mobility .
>
> Easily goes into solution in Boric Oxide , and Alkalis , forming low
> Eutectics at 985 deg.c Na2Ti05
> 806 deg.c K2Ti03
> to name a few - I made the Sodium Titanate and got a pale brown
> glass type substance , very fluid when molten at 1050 deg.c .
>
> In combination with Al203 , 2% + Ti02 , will usually fall out of solution
> in a pottery glaze upon cooling
> However when made into a frit high in Alkali and or Boric Oxide ,
> Ti02 will remain in solution and be clear .
>
> Used in an enamel or low fire pottery glaze frit , leaving out the Al203
> will allow for Ti02's use in place of Al203 . However at high
> Stoneware Temperatures you may need over 15 % Ti02, and add as
> a frit [ natural or manmade ] to obtain a clear glaze with any viscosity
.
> You could probably use the Ti02 in the place of Alkali or Alkaline or
> Boric Oxide [ or use less of each or all ].
>
> Your glaze will exhibit ultra high gloss . This is what happens when I
> make a lowfire clear glaze using Ti02 in place of Al203 .
> Ti02 has a refractive index of approximately 2.55 +
> The glaze also begins to feel like plastic or the surface of the metal
> Titanium . Run a fingernail over the surface - quite pleasant .
>
> Lastly , thank you for the information on Zirconium Oxide , very
> educational .
>
> Now can anyone say if a porcelain enamel , say for sheet steel is as
> durable , chemically or physically as a stoneware or porcelain glaze ?
> Khaimraj Seepersad
>
>
>
> -----Original Message-----
> From: Michael Banks
> To: CLAYART@LSV.UKY.EDU
> Date: 21 November 1999 13:36
> Subject: Titanium Oxide effects.
>
>
> >----------------------------Original message----------------------------
> >Maurice Cain wrote: (snip)
> >> Now here's the rub..... I've added 5% Titanium Oxide ( Dioxide?) and
> >> have observed that the glaze now runs down the pot to form a thick roll
> >> at the foot. What's happening here? Is the TiO2 acting as a fluxing
> >> agent ( melter?) and do I have to add more EPK to stiffen it up again?
> >> I'm aiming to get a lighter mottled blue.
> >
> >I've read that TiO2 is meant to stiffen glazes but have found the
opposite.
> >I tried using it as substitute for alumina (to get away from the dulling
> >effect on colour that alumina has) after reading that titanium increased
> >viscosity in Hamer. But with the glazes I was trialling (high in boric
> >oxide and zinc), white TiO2 had no stiffening effect and led to increased
> >fluidity.
> >
> >In nature, titanium-rich magmas can be quite fluid. Hawaiian basalt
> contains
> >up 3 or 4% TiO2 and is some of the runniest lava around. Most of the
> Period
> >4 transition elements (including Ti, Cu, Co, Mn etc,) appear to fluidise
> >silicate melts and must disrupt the formation of the network bonds which
is
> >a cause of viscosity.
> >
> >Titanium doesn't act too refractory in my experience either, despite the
> >high melting point of the pure oxide. The melting points of oxides are a
> >poor guide to melting behaviour in complex silicate melts and TiO2 must
> have
> >low eutectics with alkalis and other fluxes. The mineral sphene
(CaTiSiO5)
> >is 40% TiO2 and melts at ~cone 5, similar to potash feldspar.
> >
> >Michael Banks,
> >Nelson,
> >New Zealand
> >
>

Ron Roy on tue 23 nov 99

Hi Mo,

My first reaction to this was - it must not be TiO2 - however I read in
Taylor & Bull something that might make some sense. If I were you I would
double check to make sure your TiO2 is the some as someone elses.

Other oxides are "conditional glass formers" (what a great phrase - rr) The
oxides of alumina, bismuth, gallium, molybdenum, selenium, tellurium,
TITANIUM and vanadium will not form glasses on their own but will do so
when melted with a second oxide. Except for Aluminium and titanium, their
usefulness in glaze is limited. An alternative description sometimes used,
is that these are called "network modifiers."

I also see from the tables in the Hamer book that TiO2 is neutral in the
viscosity scale but fairly low in the surface tension scale.

I also see that this glaze has a fair amount of boron and the alumina is a
bit low for this type of glaze - I have noticed that you can get more
alumina into a boron glaze than other types. Is it possible this glaze was
on the verge of running and all it took was the addition of just about any
additional oxide?

Now - can someone explain to me how 5% Titania could tip a stable glaze
into a runner - it seems impossible to me.

One of the principal roles of Titania in glazes is to improve resistance to
acid attack. If the amount is under 2% it also helps craze resistance.

No - I did not make any of this up - RR

>----------------------------Original message----------------------------
>
>Dear Clayarters;
>I've researched the archives and hit the books including Hamer & Hamer
>to no avail so I turn to the Glaze Gurus for help please.
>
>In an attempt to get the perfect to die for Blue on Standard 112 clay I
>have arrived at the following recipe thanks in no small part to RR
>himself for the starting point.
>
> Frit 3134 20 19.23
> G200 FS 14 13.46
> Wollastonite 14 13.46
> Strontium 5 4.81
> Talc 8 7.69
> EPK 23 22.12
> Silica 20 19.23
>
> total 104 100%
>
>This leads to a Unity formula (1.0 flux) (0.32 AL2O3) (0.19 B2O3)
>(2.91 SiO2) which seems to be well within the limits for cone 6. 1.5%
>cobalt oxide gives the blue I'm looking for.
>
>Now here's the rub..... I've added 5% Titanium Oxide ( Dioxide?) and
>have observed that the glaze now runs down the pot to form a thick roll
>at the foot. What's happening here? Is the TiO2 acting as a fluxing
>agent ( melter?) and do I have to add more EPK to stiffen it up again?
>I'm aiming to get a lighter mottled blue.
>
>TIA mo cain exPat Brit ATLGA.

Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849

Gavin Stairs on wed 24 nov 99

Hi Ron, Mo, Michael, Khaimraj,

This is really neat stuff. Ti, which I always had pegged for a refractory,
being an active flux in the C6-stoneware range. What a hoot. From what
Khaimraj has noted, it seems that the Ti is getting dissolved in the B2O3
frit system, and that active fluid is probably eating up alumina. So the
glaze becomes fluid, not thixotropic, and runs. Solution: less Ti or frit
and more alumina (EPK), would be my guess. This is a real RR glaze: lots
of materials, all complex, except for the Strontium and Silica. But each
one contributing a simple flux. Real easy to adjust. And, for the science
skeptics, it's purpose is to be the carrier for a particular esthetic
effect. Beauty. So you can really go to town with a series of line
blends, trading off the frit against EPK, or frit to Ti, etc. Just see
what does what. Many little tiles, all in a row.

Gavin

At 12:43 PM 11/23/99 -0500, you wrote:
>----------------------------Original message----------------------------
>Hi Mo,
>
>My first reaction to this was - it must not be TiO2 - however I read in
>Taylor & Bull something that might make some sense. If I were you I would
>double check to make sure your TiO2 is the some as someone elses.
>
>Other oxides are "conditional glass formers" (what a great phrase - rr) The
>oxides of alumina, bismuth, gallium, molybdenum, selenium, tellurium,
>TITANIUM and vanadium will not form glasses on their own but will do so
>when melted with a second oxide. Except for Aluminium and titanium, their
>usefulness in glaze is limited. An alternative description sometimes used,
>is that these are called "network modifiers."
>
>I also see from the tables in the Hamer book that TiO2 is neutral in the
>viscosity scale but fairly low in the surface tension scale.
>
>I also see that this glaze has a fair amount of boron and the alumina is a
>bit low for this type of glaze - I have noticed that you can get more
>alumina into a boron glaze than other types. Is it possible this glaze was
>on the verge of running and all it took was the addition of just about any
>additional oxide?
>
>Now - can someone explain to me how 5% Titania could tip a stable glaze
>into a runner - it seems impossible to me.
>
>One of the principal roles of Titania in glazes is to improve resistance to
>acid attack. If the amount is under 2% it also helps craze resistance.
>
>No - I did not make any of this up - RR
>
>>----------------------------Original message----------------------------
>>
>>Dear Clayarters;
>>I've researched the archives and hit the books including Hamer & Hamer
>>to no avail so I turn to the Glaze Gurus for help please.

Gavin Stairs on wed 24 nov 99

Hi Ron, Mo, Michael, Khaimraj,

I just had a thought which ties this in with another observation. It is
said that a TiO2 oxide layer makes an opaque white (as in painting: see
thread on gesso), but that it is unreliable as an underglaze. Now that
makes sense: this is used in low temp work, like Maiolica, where the
glazes must be high B2O3 and alkali, which would eat the Ti. Thank you all
for making sense of this for me.

Gavin

Khaimraj Seepersad on thu 25 nov 99

Hee hee he ,
Just to be mischievous ,
But Gavin if you balance to B203 [ 8 to 16 % ] , Alkali [ 10 to 18 % ]
and add just a bit more Ti02 [ 8 to 20 % ] , a little Al203 [ say 13 % ]
or a bit of P205 [ 6 % + ] ,
you get booootiful White to Blue White Majolica Glazes from
850 to 1125 deg.c
See your Parmelee reprint . pg 18

The unreliability in Ti02 as an underglaze colour seems to
stem from the changing phase [ anatase , rutile ] as well
as it's affinity for iron .
Khaimraj


-----Original Message-----
From: Gavin Stairs
To: CLAYART@LSV.UKY.EDU
Date: 24 November 1999 5:43
Subject: Re: Titanium Oxide effects.


----------------------------Original message----------------------------
Hi Ron, Mo, Michael, Khaimraj,

I just had a thought which ties this in with another observation. It is
said that a TiO2 oxide layer makes an opaque white (as in painting: see
thread on gesso), but that it is unreliable as an underglaze. Now that
makes sense: this is used in low temp work, like Maiolica, where the
glazes must be high B2O3 and alkali, which would eat the Ti. Thank you all
for making sense of this for me.

Gavin

Ray Aldridge on thu 25 nov 99

At 08:46 AM 11/24/99 EST, you wrote:
>----------------------------Original message----------------------------
>Hi Ron, Mo, Michael, Khaimraj,
>
>I just had a thought which ties this in with another observation. It is
>said that a TiO2 oxide layer makes an opaque white (as in painting: see
>thread on gesso), but that it is unreliable as an underglaze.

Let me ask the gurus another question about titania. Why, when I add 6 or
7% TiO2 to Vince's Alltemp White slip, do I get a fairly bright yellow at C8?

Ray


Aldridge Porcelain and Stoneware
http://www.goodpots.com

Ron Roy on fri 26 nov 99

So - adding TiO2 to a glaze with enough alkalies and/or boron can result in
more melt - if you are moving towards a eutectic - if moving away from a
eutectic I would expect less melt - Is this a possible explanation?

I know that when I started to understand about eutectics I thought it
helped to explain the strange ((to me) phenomenon like when alumina is
added to a glaze it gets shinier and more runny before it stiffens
sometimes - particularly when there is enough boron present.

RR

Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849

ababy sharon on sat 27 nov 99

With all it`s beauty, I wonder, why I never see Titanium in any Raku recipe,
I don,t mean 2% but 20 !
Ababi
----- Original Message -----
From: Khaimraj Seepersad
To:
Sent: Thursday, November 25, 1999 05:34
Subject: Re: Titanium Oxide effects.


> ----------------------------Original message----------------------------
> Hee hee he ,
> Just to be mischievous ,
> But Gavin if you balance to B203 [ 8 to 16 % ] , Alkali [ 10 to 18 % ]
> and add just a bit more Ti02 [ 8 to 20 % ] , a little Al203 [ say 13 % ]
> or a bit of P205 [ 6 % + ] ,
> you get booootiful White to Blue White Majolica Glazes from
> 850 to 1125 deg.c
> See your Parmelee reprint . pg 18
>
> The unreliability in Ti02 as an underglaze colour seems to
> stem from the changing phase [ anatase , rutile ] as well
> as it's affinity for iron .
> Khaimraj
>
>
> -----Original Message-----
> From: Gavin Stairs
> To: CLAYART@LSV.UKY.EDU
> Date: 24 November 1999 5:43
> Subject: Re: Titanium Oxide effects.
>
>
> ----------------------------Original message----------------------------
> Hi Ron, Mo, Michael, Khaimraj,
>
> I just had a thought which ties this in with another observation. It is
> said that a TiO2 oxide layer makes an opaque white (as in painting: see
> thread on gesso), but that it is unreliable as an underglaze. Now that
> makes sense: this is used in low temp work, like Maiolica, where the
> glazes must be high B2O3 and alkali, which would eat the Ti. Thank you
all
> for making sense of this for me.
>
> Gavin
>
>

Michael Banks on sun 28 nov 99

Yes, I think you are quite correct here Ron. In many cases initially adding
some TiO2 could be expected to push the composition towards a lower
eutectic, as do many oxides when added to a certain point, including
refractories such as alumina (as you have noted).

Overdosing a glaze in TiO2 results in rapid crystal matting on cooling (as
most potters know), but titanium also seems to shove other transition metals
out of solution ahead of it on cooling, particularly zinc, cobalt,
molybdenum and nickel. As some of these are more powerful fluxes than Ti
(which cannot probably be called a true flux, more a fluidiser perhaps),
macrocrystals of zinc silicate popping out of solution ahead of titanium in
a zinc crystal glaze, would push the remaining molten glaze composition away
from the low zinc eutectic. This may be why titanium improves zinc
macrocrystal glazes. It forces Zn, Co, Ni etc, to form bigger crystals
earlier in the cooling cycle and the loss of these fluxes causes the
remaining glaze to freeze earlier than it would have, remaining glossy and
smooth.

Too much TiO2 though, causes matting-over of the entire glaze surface as a
lot of the TiO2 plummets out of solution early on. Most glazes will absorb
more TiO2 than say cobalt oxide though (even though Co is an active flux)
and cobalt scums-out if added in excess of a few percent. This is because
Ti bonds easily to silicate structures (in geochemists jargon it shows
"lithophile" nature) relative to Co, Cu, Ni, Mo and even Zn, which are
"chalcophile" (having more affinity to sulphide structures).

Michael Banks,
Nelson,
New Zealand


Ron Roy wrote:
> ----------------------------Original message----------------------------
> So - adding TiO2 to a glaze with enough alkalies and/or boron can result
in
> more melt - if you are moving towards a eutectic - if moving away from a
> eutectic I would expect less melt - Is this a possible explanation?
>
> I know that when I started to understand about eutectics I thought it
> helped to explain the strange ((to me) phenomenon like when alumina is
> added to a glaze it gets shinier and more runny before it stiffens
> sometimes - particularly when there is enough boron present.

Louis H.. Katz on sat 18 dec 99

Yellow from titanium dioxide?
Some one else can tell me I am wrong, but my assumption on that one, having run
into the same routine myself is that Titanium Dioxide often contains a good bit
of iron unless the iron has been removed. Looked just like light rutile to me
once I fired it. Ran some expiriments after I was given 1800 pounds of Titanium
dioxide.
Louis

Ray Aldridge wrote:

> ----------------------------Original message----------------------------
> At 08:46 AM 11/24/99 EST, you wrote:
> >----------------------------Original message----------------------------
> >Hi Ron, Mo, Michael, Khaimraj,
> >
> >I just had a thought which ties this in with another observation. It is
> >said that a TiO2 oxide layer makes an opaque white (as in painting: see
> >thread on gesso), but that it is unreliable as an underglaze.
>
> Let me ask the gurus another question about titania. Why, when I add 6 or
> 7% TiO2 to Vince's Alltemp White slip, do I get a fairly bright yellow at C8?
>
> Ray
>
> Aldridge Porcelain and Stoneware
> http://www.goodpots.com

Michael Banks on sun 19 dec 99

You're right Louis,

Even analytical grade white titanium dioxide (the purest around, with next
to nil iron content) will scavenge iron from other sources in the glaze or
body to make various shades of cream, amber, yellows and browns. TiO2 has a
very strong affinity for iron, evidenced by the fact that natural rutile is
never found in the colourless clear form but is usually dark red to black.
These dark colours in natural rutile are caused by iron, predominantly and
the crystal structure can accommodate up to 32 weight percent without
cracking up. This is a lot of iron (only 5% less than ilmenite) and
indicates how cosy these two elements are together.

Brighter yellows are possible in lime glazes due to sphene (or titanite,
CaTiSiO4) crystallites, which again are coloured by scavenged iron.

The ability of TiO2 to texture glaze is due to a steep positive solubility
curve in respect to temperature, meaning that as the molten glaze cools,
TiO2 crystals precipitate out and they yank out any ambient iron with them.
Even pure white clay bodies commonly have 0.5% iron oxide content, which is
more than enough Fe available close to the glaze interface to strongly
colour TiO2 crystals.

Michael Banks,
Nelson,
New Zealand


> ----------------------------Original message----------------------------
> Yellow from titanium dioxide?
> Some one else can tell me I am wrong, but my assumption on that one,
having run
> into the same routine myself is that Titanium Dioxide often contains a
good bit
> of iron unless the iron has been removed. Looked just like light rutile to
me
> once I fired it. Ran some expiriments after I was given 1800 pounds of
Titanium
> dioxide.
> Louis
>
> Ray Aldridge wrote:
>
> > ----------------------------Original message----------------------------
> > At 08:46 AM 11/24/99 EST, you wrote:
> > >----------------------------Original
message----------------------------
> > >Hi Ron, Mo, Michael, Khaimraj,
> > >
> > >I just had a thought which ties this in with another observation. It
is
> > >said that a TiO2 oxide layer makes an opaque white (as in painting: see
> > >thread on gesso), but that it is unreliable as an underglaze.
> >
> > Let me ask the gurus another question about titania. Why, when I add 6
or
> > 7% TiO2 to Vince's Alltemp White slip, do I get a fairly bright yellow
at C8?
> >
> > Ray
> >
> > Aldridge Porcelain and Stoneware
> > http://www.goodpots.com
>

Edouard Bastarache on sun 19 dec 99

------------------
Hello

it probably depends on the =22grade=22 of Titanium dioxide you use.
I work for a titanium dioxide maker (Tioxide of Canada) as a
consultant and they suggested i use their TR92 because it is
zirconium coated, to make whites.
Here is their analysis:

Al2O3 2.8-3.8=25
P2O5 0.3-0.55=25
ZrO2 0.45-0.8=25
TIO2 932-95.2=25
Carbon 0.10-0.16=25
Iron Total 100ppm (Max)

Here is the analysis of another grade they make,
AHR,which was used by a ceramics company
in the region of Buffalo:

K20 0.28-0.40=25
P2O5 0.50-0.70=25
TiO2 98-99=25
Carbon 0.10-0.16=25
Iron Total 50ppm(Max)

Later




Edouard Bastarache
edouardb=40sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/=7Eedouardb/
-----Message d'origine-----
De : Louis H.. Katz =3Clkatz=40falcon.tamucc.edu=3E
=C0 : CLAYART=40LSV.UKY.EDU =3CCLAYART=40LSV.UKY.EDU=3E
Date : 18 d=E9cembre, 1999 19:57
Objet : Re: Titanium Oxide effects.


=3E----------------------------Original message----------------------------
=3EYellow from titanium dioxide?
=3ESome one else can tell me I am wrong, but my assumption on that one, =
having
run
=3Einto the same routine myself is that Titanium Dioxide often contains a =
good
bit
=3Eof iron unless the iron has been removed. Looked just like light rutile =
to
me
=3Eonce I fired it. Ran some expiriments after I was given 1800 pounds of
Titanium
=3Edioxide.
=3ELouis
=3E
=3ERay Aldridge wrote:
=3E
=3E=3E ----------------------------Original =
message----------------------------
=3E=3E At 08:46 AM 11/24/99 EST, you wrote:
=3E=3E =3E----------------------------Original =
message----------------------------
=3E=3E =3EHi Ron, Mo, Michael, Khaimraj,
=3E=3E =3E
=3E=3E =3EI just had a thought which ties this in with another observation. =
It is
=3E=3E =3Esaid that a TiO2 oxide layer makes an opaque white (as in =
painting: see
=3E=3E =3Ethread on gesso), but that it is unreliable as an underglaze.
=3E=3E
=3E=3E Let me ask the gurus another question about titania. Why, when I add=
6 o
r
=3E=3E 7=25 TiO2 to Vince's Alltemp White slip, do I get a fairly bright =
yellow at
C8?
=3E=3E
=3E=3E Ray
=3E=3E
=3E=3E Aldridge Porcelain and Stoneware
=3E=3E http://www.goodpots.com

Khaimraj Seepersad on mon 20 dec 99

Good Afternoon to All ,
To : Michael -

As usual , thank you for the reply ,

here 's my question - since Titanium dioxide , has such affinity
for iron , is there any information to prove or show that Ti02
may stabilise small quantities of Cuo , Co , and other colouring
oxides in glass .

I was looking at the results on Mr . Hesselberth's Site , and
wondered if Ti02 might have a positive effect on oxides
of colour .

I noted that 30 Na20 + 29 Ti02 + 41 Si02 , was a very stable
glass . Ti02 obviously has some hidden or unexplored qualities.

Later next year , I will test some Niobium Oxide from surgical
quality Niobium , and let you know what it does when incorporated
into a frit [ Alkaline and Borosilicate ] .

Thank you for the e-mail , hoping to return the serve.
But it is too early to start the Seasons Greetings .
Khaimraj Seepersad


-----Original Message-----
From: Michael Banks
To: CLAYART@LSV.UKY.EDU
Date: 19 December 1999 7:48
Subject: Titanium Oxide effects.


>----------------------------Original message----------------------------
>You're right Louis,
>
>Even analytical grade white titanium dioxide (the purest around, with next
>to nil iron content) will scavenge iron from other sources in the glaze or
>body to make various shades of cream, amber, yellows and browns. TiO2 has
a
>very strong affinity for iron, evidenced by the fact that natural rutile is
>never found in the colourless clear form but is usually dark red to black.
>These dark colours in natural rutile are caused by iron, predominantly and
>the crystal structure can accommodate up to 32 weight percent without
>cracking up. This is a lot of iron (only 5% less than ilmenite) and
>indicates how cosy these two elements are together.
>
>Brighter yellows are possible in lime glazes due to sphene (or titanite,
>CaTiSiO4) crystallites, which again are coloured by scavenged iron.
>
>The ability of TiO2 to texture glaze is due to a steep positive solubility
>curve in respect to temperature, meaning that as the molten glaze cools,
>TiO2 crystals precipitate out and they yank out any ambient iron with them.
>Even pure white clay bodies commonly have 0.5% iron oxide content, which is
>more than enough Fe available close to the glaze interface to strongly
>colour TiO2 crystals.
>
>Michael Banks,
>Nelson,
>New Zealand
>
>
>> ----------------------------Original message----------------------------
>> Yellow from titanium dioxide?
>> Some one else can tell me I am wrong, but my assumption on that one,
>having run
>> into the same routine myself is that Titanium Dioxide often contains a
>good bit
>> of iron unless the iron has been removed. Looked just like light rutile
to
>me
>> once I fired it. Ran some expiriments after I was given 1800 pounds of
>Titanium
>> dioxide.
>> Louis
>>
>> Ray Aldridge wrote:
>>
>> > ----------------------------Original
message----------------------------
>> > At 08:46 AM 11/24/99 EST, you wrote:
>> > >----------------------------Original
>message----------------------------
>> > >Hi Ron, Mo, Michael, Khaimraj,
>> > >
>> > >I just had a thought which ties this in with another observation. It
>is
>> > >said that a TiO2 oxide layer makes an opaque white (as in painting:
see
>> > >thread on gesso), but that it is unreliable as an underglaze.
>> >
>> > Let me ask the gurus another question about titania. Why, when I add 6
>or
>> > 7% TiO2 to Vince's Alltemp White slip, do I get a fairly bright yellow
>at C8?
>> >
>> > Ray
>> >
>> > Aldridge Porcelain and Stoneware
>> > http://www.goodpots.com
>>
>