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potty
September 9th 03, 09:46 AM
Can anybody tell me if toxic oxides used as inglazes (applied to glaze
surface before firing) remain harmful after being taken to 9 or, for
that matter, any stoneware temperature? Not for food use, of course, but
general handling. In this particular case I am concerned about a pot we
made with large areas of vanadium pentoxide decoration. Before washing,
these areas were quite dusty, presumably, with cooked vanadium. The
glaze is a kaolin and ash mix with copper carbonate and iron oxide
additions.
Thanks
Pete

Dewitt
September 9th 03, 04:09 PM
On Tue, 09 Sep 2003 09:46:16 +0100, potty >
wrote:

>Can anybody tell me if toxic oxides used as inglazes (applied to glaze
>surface before firing) remain harmful after being taken to ?9 or, for
>that matter, any stoneware temperature? Not for food use, of course, but
>general handling. In this particular case I am concerned about a pot we
>made with large areas of vanadium pentoxide decoration. Before washing,
>these areas were quite dusty, presumably, with cooked vanadium. The
>glaze is a kaolin and ash mix with copper carbonate and iron oxide
>additions.
>Thanks
>Pete

In a word - YES. Toxic oxides stay toxic no matter what temperature
they are fired to. After firing, the question becomes whether the
glaze is stable enough so that the oxides don't leach out. What
you've described as your glaze is almost certainly far from a stable
glaze. Certainly, if the pot came out the kiln "dusty" it is not a
stable glaze. As the robot on "Lost in Space" was fond of saying,
"Danger, Will Robinson, Danger!"

deg

potty
September 10th 03, 12:15 AM
> In a word - YES. Toxic oxides stay toxic no matter what temperature
> they are fired to. After firing, the question becomes whether the
> glaze is stable enough so that the oxides don't leach out. What
> you've described as your glaze is almost certainly far from a stable
> glaze. Certainly, if the pot came out the kiln "dusty" it is not a
> stable glaze. As the robot on "Lost in Space" was fond of saying,
> "Danger, Will Robinson, Danger!"

Thanks deg, I thought as much. I take this to mean that the only safe
in-glaze decoration will be with iron, rutile , ilmenite and
commercially available food-safe products. Does the same go for on-glaze
and lustre finishes as virtually all lustres are toxic?
Pete

Dewitt
September 10th 03, 04:50 AM
On Wed, 10 Sep 2003 00:15:47 +0100, potty >
wrote:

>Thanks deg, I thought as much. I take this to mean that the only safe
>in-glaze decoration will be with iron, rutile , ilmenite and
>commercially available food-safe products. Does the same go for on-glaze
>and lustre finishes as virtually all lustres are toxic?
>Pete

Using non-toxic (or nearly so) oxides is the safest way to go unless
you are sure that your glaze is stable and not leaching excessive
amounts of the oxides. The only sure way to know this is to have your
glazes leach tested. You can find more info on glaze stability and
info on where to get your glazes test at www.frogpondpottery.com Even
some commercial glazes leach more than they should. Some can show a
color change just by having a lemon slice left to sit on them.

deg



deg

September 26th 03, 05:22 PM
Yes Deg,
you're right, definitly. In fact, here in Italy, is strictly prohibited to
use vanadium pentoxide, no matter which glaze you're using on your ceramics.

Have a good day!

Luca

--
Luca Napoli
Ceramica D'Amore
Fine Italian Handmade Ceramics
VIETRI - ITALY
www.ceramicadamore.com




"Dewitt" > ha scritto nel messaggio
...
> On Tue, 09 Sep 2003 09:46:16 +0100, potty >
> wrote:
>
> >Can anybody tell me if toxic oxides used as inglazes (applied to glaze
> >surface before firing) remain harmful after being taken to ?9 or, for
> >that matter, any stoneware temperature? Not for food use, of course, but
> >general handling. In this particular case I am concerned about a pot we
> >made with large areas of vanadium pentoxide decoration. Before washing,
> >these areas were quite dusty, presumably, with cooked vanadium. The
> >glaze is a kaolin and ash mix with copper carbonate and iron oxide
> >additions.
> >Thanks
> >Pete
>
> In a word - YES. Toxic oxides stay toxic no matter what temperature
> they are fired to. After firing, the question becomes whether the
> glaze is stable enough so that the oxides don't leach out. What
> you've described as your glaze is almost certainly far from a stable
> glaze. Certainly, if the pot came out the kiln "dusty" it is not a
> stable glaze. As the robot on "Lost in Space" was fond of saying,
> "Danger, Will Robinson, Danger!"
>
> deg

Steve Mills
September 28th 03, 12:06 AM
For your interest the following is taken from the UK Health & Safety
Data Sheet for Vanadium Pentoxide (MSDS)

Section 15 Regulatory information

EC Supply Labelling T Toxic Dangerous for the Environment
R(Risk)-Phrases
R20/22 Harmful by inhalation and if swallowed
R37 Irritating to respiratory system
R40 Possible risk of irreversible effects
R48/23 Toxic: Danger of serious damage to health by
prolonged exposure through inhalation
R51/53 Toxic to aquatic organisms, may cause long term
adverse effects in the aquatic environment.
R63 Possible risk of harm to the unborn child
S(Safety)-Phrases
S13 keep away from food, drink and animal feeding stuff
S20/21 when using do not eat, drink or smoke
S22/23 do not breathe dust or spray
S36/37 wear suitable protective clothing
S38 In case of insufficient ventilation wear suitable respiratory
equipment
S45 In case of accident or if you feel unwell seek medical advice
immediately (show label where possible).
S61 Avoid release to the environment. Refer to special
instructions/ safety data sheet


Steve
Bath
UK


In article >,
writes
>Yes Deg,
>you're right, definitly. In fact, here in Italy, is strictly prohibited to
>use vanadium pentoxide, no matter which glaze you're using on your ceramics.
>
>Have a good day!
>
> Luca
>

--
Steve Mills
Bath
UK

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