ivor and olive lewis on wed 20 oct 10
Fluorite is a natural mineral attributed with the properties of a Flux (In
Iron smelting, enamelling, Fluorine production and glass making.
The 18th edition of Dana's Manual of Mineralogy claims fusion at level 3 in
the scale of fusibility,(p206) approximating to 1050 deg Celsius. As the
chemical compound Calcium Fluoride has a melting point 1360 deg Celsius
(Kaye and Laby, p 157 ,1982) 1110 deg C (CRC Handbook).
Its Molecular Formula is CaF2.
It might be interesting to speculate on its ability to cause fusion or
melting in glazes compounded to mature at or below Orton Cone 6. Were it to
enter into a chemical reaction with Sodium Oxide below this fusion point on=
e
product might (hypothetically) be Sodium Fluoride which has a fusion point
of 988/996 deg Celsius which might act as a solvent for more refractory
materials, as do Sodium Carbonate.and Sodium nitrate.
Ivor Lewis,
REDHILL,
South Australia
C Sullivan on wed 20 oct 10
Re: Robert Harris' observations.
I think the info you mentioned is found in Obstler's, "Out of the Earth,
Into the Fire". I've read that too, but still a couple of years back,
decided to try fluorite in a couple of my glazes. Had windows and door wid=
e
open and plenty of ventilation.
It was the first and only time, fumes from the firing really whomped me.
Have never messed with it since.
Chae
On Wed, Oct 20, 2010 at 5:37 AM, Robert Harris wro=
te:
> Ivor,
>
> I'm not sure if this post was just a random musing, or in reply to
> something else, but I've been long under the impression that Fluorspar
> aka fluorite would decompose in glazes during firing, giving off
> fluorine gas or HF gas (depending on which source).
>
> Having said that a quick search on the internet for this phenomenon
> only shows evidence from places like digitalfire which contends that
> "CaF2 reacts with oxygen at high temperatures to form CaO and F2".
> However I cannot find any other source for this reaction.
>
> I imagine that small quantities of HF might also be released since
> CaF2 will react with sulphuric acid to form HF. While the amounts of
> sulphur might be small it is probably enough to produce HF. Indeed the
> commercial production of HF is a byproduct of phosphoric acid, using
> the fact that small contaminating amounts of sulphur and fluorapatite
> are found in apatite ores. When heated, these ores give off HF and
> sulphuric acid.
>
> Anecdotally the presence of small amounts of HF from a firing is why
> kiln rooms always get clouded windows...
>
> Anyway, I've always been told that fluorine based minerals are bad
> news in glazes FWIW.
>
> Robert
>
>
> On Wed, Oct 20, 2010 at 1:28 AM, ivor and olive lewis
> wrote:
> > Fluorite is a natural mineral attributed with the properties of a Flux
> (In
> > Iron smelting, enamelling, Fluorine production and glass making.
> > The 18th edition of Dana's Manual of Mineralogy claims fusion at level =
3
> in
> > the scale of fusibility,(p206) approximating to 1050 deg Celsius. As th=
e
> > chemical compound Calcium Fluoride has a melting point 1360 deg Celsius
> > (Kaye and Laby, p 157 ,1982) 1110 deg C (CRC Handbook).
> > Its Molecular Formula is CaF2.
> > It might be interesting to speculate on its ability to cause fusion or
> > melting in glazes compounded to mature at or below Orton Cone 6. Were i=
t
> to
> > enter into a chemical reaction with Sodium Oxide below this fusion poin=
t
> one
> > product might (hypothetically) be Sodium Fluoride which has a fusion
> point
> > of 988/996 deg Celsius which might act as a solvent for more refractory
> > materials, as do Sodium Carbonate.and Sodium nitrate.
> >
> > Ivor Lewis,
> > REDHILL,
> > South Australia
> >
>
>
>
> --
> ----------------------------------------------------------
>
Edouard Bastarache on wed 20 oct 10
Fluorite=3D3DFluorspar=3D3D
http://www.statcan.gc.ca/pub/82-581-x/2006001/projects/4158951-eng.htm
Newfoundland Fluorspar Miners Mortality and Cancer Incidence Study: =3D
Radon-Progeny Exposure and Lung Cancer Risk Study=3D20
Description of project
The purpose of the project was to assess the potential occupational =3D
health risks that existed among Newfoundland fluorspar miners. Analysis =3D
of the data showed that the risk of dying of lung cancer is strongly =3D
associated with cumulative radon daughter exposure.
Alcan that owned for decades the largest aluminum smelter in the world =3D
in my home-town used Fluorspar to help melt calcined alumina to aluminum =
=3D
metal. I believe they gave up using it after the results of the above =3D
study.
Gis,
Edouard Bastarache=3D20
Spertesperantisto=3D20
Sorel-Tracy
Quebec
http://www.flickr.com/photos/30058682@N00/
http://edouardbastarache.blogspot.com/
http://blogsalbertbastarache.blogspot.com/
http://cerampeintures.blogspot.com/
http://www.facebook.com/edouard.bastarache
Robert Harris on wed 20 oct 10
Ivor,
I'm not sure if this post was just a random musing, or in reply to
something else, but I've been long under the impression that Fluorspar
aka fluorite would decompose in glazes during firing, giving off
fluorine gas or HF gas (depending on which source).
Having said that a quick search on the internet for this phenomenon
only shows evidence from places like digitalfire which contends that
"CaF2 reacts with oxygen at high temperatures to form CaO and F2".
However I cannot find any other source for this reaction.
I imagine that small quantities of HF might also be released since
CaF2 will react with sulphuric acid to form HF. While the amounts of
sulphur might be small it is probably enough to produce HF. Indeed the
commercial production of HF is a byproduct of phosphoric acid, using
the fact that small contaminating amounts of sulphur and fluorapatite
are found in apatite ores. When heated, these ores give off HF and
sulphuric acid.
Anecdotally the presence of small amounts of HF from a firing is why
kiln rooms always get clouded windows...
Anyway, I've always been told that fluorine based minerals are bad
news in glazes FWIW.
Robert
On Wed, Oct 20, 2010 at 1:28 AM, ivor and olive lewis
wrote:
> Fluorite is a natural mineral attributed with the properties of a Flux (I=
n
> Iron smelting, enamelling, Fluorine production and glass making.
> The 18th edition of Dana's Manual of Mineralogy claims fusion at level 3 =
in
> the scale of fusibility,(p206) approximating to 1050 deg Celsius. As the
> chemical compound Calcium Fluoride has a melting point 1360 deg Celsius
> (Kaye and Laby, p 157 ,1982) 1110 deg C (CRC Handbook).
> Its Molecular Formula is CaF2.
> It might be interesting to speculate on its ability to cause fusion or
> melting in glazes compounded to mature at or below Orton Cone 6. Were it =
to
> enter into a chemical reaction with Sodium Oxide below this fusion point =
one
> product might (hypothetically) be Sodium Fluoride which has a fusion poin=
t
> of 988/996 deg Celsius which might act as a solvent for more refractory
> materials, as do Sodium Carbonate.and Sodium nitrate.
>
> Ivor Lewis,
> REDHILL,
> South Australia
>
--
----------------------------------------------------------
ivor and olive lewis on thu 21 oct 10
Edouard,
Radon is, as I understand things, a decay product of Radium 226. As a =3D
member of the inert gas group it will have limited chemical activity. In =
=3D
South Australia this gas is associated with Hot Springs occurring in the =
=3D
northern regions of the Adelaide Geosyncline.
Cryolite is another mineral containing Fluorine used as a flux in the =3D
smelting of aluminium.
Regards,
Ivor Lewis,
REDHILL,
South Australia
----- Original Message -----=3D20
From: Edouard Bastarache=3D20
To: Clayart ; ivor and olive lewis=3D20
Sent: Thursday, October 21, 2010 2:00 AM
Subject: Re: Ceramic Materials>Natural Minerals>Fluorides>Fluorite
Fluorite=3D3DFluorspar=3D3D
http://www.statcan.gc.ca/pub/82-581-x/2006001/projects/4158951-eng.htm
Newfoundland Fluorspar Miners Mortality and Cancer Incidence Study: =3D
Radon-Progeny Exposure and Lung Cancer Risk Study=3D20
Description of project
The purpose of the project was to assess the potential occupational =3D
health risks that existed among Newfoundland fluorspar miners. Analysis =3D
of the data showed that the risk of dying of lung cancer is strongly =3D
associated with cumulative radon daughter exposure.
Alcan that owned for decades the largest aluminum smelter in the world =
=3D
in my home-town used Fluorspar to help melt calcined alumina to aluminum =
=3D
metal. I believe they gave up using it after the results of the above =3D
study.
Gis,
Edouard Bastarache=3D20
Spertesperantisto=3D20
Sorel-Tracy
Quebec
http://www.flickr.com/photos/30058682@N00/
http://edouardbastarache.blogspot.com/
http://blogsalbertbastarache.blogspot.com/
http://cerampeintures.blogspot.com/
http://www.facebook.com/edouard.bastarache
=3D20
Edouard Bastarache on thu 21 oct 10
Ivor,
decades ago Alcan switched to Cryolite
Gis,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.flickr.com/photos/30058682@N00/
http://edouardbastarache.blogspot.com/
http://blogsalbertbastarache.blogspot.com/
http://cerampeintures.blogspot.com/
http://www.facebook.com/edouard.bastarache
----- Original Message -----
From: "ivor and olive lewis"
To:
Sent: Thursday, October 21, 2010 12:00 AM
Subject: Re: Ceramic Materials>Natural Minerals>Fluorides>Fluorite
Edouard,
Radon is, as I understand things, a decay product of Radium 226. As a membe=
r
of the inert gas group it will have limited chemical activity. In South
Australia this gas is associated with Hot Springs occurring in the northern
regions of the Adelaide Geosyncline.
Cryolite is another mineral containing Fluorine used as a flux in the
smelting of aluminium.
Regards,
Ivor Lewis,
REDHILL,
South Australia
----- Original Message -----
From: Edouard Bastarache
To: Clayart ; ivor and olive lewis
Sent: Thursday, October 21, 2010 2:00 AM
Subject: Re: Ceramic Materials>Natural Minerals>Fluorides>Fluorite
Fluorite=3DFluorspar=3D
http://www.statcan.gc.ca/pub/82-581-x/2006001/projects/4158951-eng.htm
Newfoundland Fluorspar Miners Mortality and Cancer Incidence Study:
Radon-Progeny Exposure and Lung Cancer Risk Study
Description of project
The purpose of the project was to assess the potential occupational healt=
h
risks that existed among Newfoundland fluorspar miners. Analysis of the dat=
a
showed that the risk of dying of lung cancer is strongly associated with
cumulative radon daughter exposure.
Alcan that owned for decades the largest aluminum smelter in the world in
my home-town used Fluorspar to help melt calcined alumina to aluminum metal=
.
I believe they gave up using it after the results of the above study.
Gis,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.flickr.com/photos/30058682@N00/
http://edouardbastarache.blogspot.com/
http://blogsalbertbastarache.blogspot.com/
http://cerampeintures.blogspot.com/
http://www.facebook.com/edouard.bastarache
ivor and olive lewis on fri 22 oct 10
Steve,
Radon is a distraction and throws no light on the ability of Calcium
Fluoride to perform as a fluxing agent in a glaze batch or the way it
behaves in the presence of other glaze ingredients..
One might wonder at the fight taking place over the potash deposits in
Canada at the moment. Is this derived from deep seated granite emplacements
and contain radioactive minerals ? And is it a product used by ceramic
manufacturers. Do Canadian potters use Canadian Potash?
By the way, don't the Inert Gases have monatomic molecules ?
Regards,
Ivor Lewis,
REDHILL,
South Australia
----- Original Message -----
From: "Steve Slatin"
To: ; "ivor and olive lewis"
Sent: Friday, October 22, 2010 12:23 PM
Subject: Re: Ceramic Materials>Natural Minerals>Fluorides>Fluorite
> The issue with radon isn't chemical stability, as you note,
> it's a noble gas. The issue is radioactive decay -- radon
> is both a product of radioactive decay (from radium) and
> a parent through decay of polonium. Which is itself highly
> radioactive and decays through something like eight separate
> activities until it becomes a stable element. There are both
> alpha and beta emissions, so there's plenty of radiation
> there, during which all of the products of the radon are
> metals -- so you inhale one molecule of radon, and if it
> decays you probably get all 8 radiation events right in
> your lungs, one after another.
>
> Steve Slatin --
>
> N48.0886450
> W123.1420482
>
>
> --- On Wed, 10/20/10, ivor and olive lewis wrote:
>
>> Edouard,
>> Radon is, as I understand things, a decay product of Radium
>> 226. As a member of the inert gas group it will have limited
>> chemical activity. In South Australia this gas is associated
>> with Hot Springs occurring in the northern regions of the
>> Adelaide Geosyncline.
>
>
>
>
>
douglas fur on fri 29 oct 10
Ivor Lewis,
"Cryolite is another mineral containing Fluorine used as a flux in the
> smelting of aluminium."
> Cryolite is an intesting ceramic flux- (my impression is that it was key =
to
> the Natzlers' lava glazes) My first contact with it was as a work study
> student schlepping materials to the basement. Dusting off a bag tofind ou=
t
> what it was I read the label CRYO-CIDE and application instructions for
> controling mexican bean leaf rollers...
In glazes I think the churning of the galze as the F2 escapes the melt may
promote the melt and the healed craters can produce an interesting mottling=
.
DRB
Seola Creek
ivor and olive lewis on sat 30 oct 10
Dear DRB,
I asked my original question because ideas printed in the name of =3D
science for potters and ceramic artists do not sit well when compared to =
=3D
what can be found in general chemical text books. To put it another way, =
=3D
most of what has been printed for us clayworkers seems to be conjecture =3D
and/or assumption..
One simple way of showing this is to do the thermodynamic calculations =3D
for the proposed reactions. My attempt to do this for Fluorite, Calcium =3D
Fluoride, suggest that in contact with a compound containing one of the =3D
alkali metal oxides (Na2O or K2O) the resultant products would be, =3D
spontaneously, Sodium fluoride or Potassium fluoride. Interesting in =3D
terms of fluxing activity because both products have relatively low =3D
melting points when compared to Calcium Oxide or even a Cone Six firing.
Also ignored are compounds such as Silicon tetrafluoride, a highly =3D
reactive, toxic gas at room temperature.
Interesting about the insecticidal properties of Cryolite.
Regards
Ivor Lewis,
REDHILL,
South Australia
Ivor Lewis,
"Cryolite is another mineral containing Fluorine used as a flux in the =
=3D
smelting of aluminium."
Cryolite is an intesting ceramic flux- (my impression is that it was =
=3D
key to the Natzlers' lava glazes) My first contact with it was as a =3D
work study student schlepping materials to the basement. Dusting off a =3D
bag tofind out what it was I read the label CRYO-CIDE and application =3D
instructions for controling mexican bean leaf rollers...
In glazes I think the churning of the galze as the F2 escapes the melt =
=3D
may promote the melt and the healed craters can produce an interesting =3D
mottling.
DRB
Seola Creek
| |
|
