Duff bogen on mon 14 apr 08
Ivor et al.
As I put my lip to a new cup, the thought arose "Is this safe?" and I couldn't answer myself with 100% satisfaction. The slip is ~90% a high iron lateritic clay-soil and ~10% MnO2. It fuses at ^6 but I wonder about Mn leechinig out and its toxicity.
What are your impressions of this situation?
DRB
Seattle
Ivor and Olive Lewis wrote:
Dear John Sankey,
<<"phosphorus [is] normally an insoluble non-conductor"
Elemental phosphorus is a metal, conductivity 10 milliohm-cm. For comparison: iron (again, elemental) is 9.7, magnesium 4.4>>
I am not sure which definitions of Metal and Non Metal you are using. Since there is a clear conflict here, perhaps you would provide definitions.
Phosphorus is not listed by Kaye and Laby,"Tables of Physical and Chemical Constants", in their table of Resistivities of Metallic Elements, PP 102-3,
My experience of handling Phosphorus is that it is a Semi Transparent Yellow Wax like substance that stored under water and is easily cut with the blade of a knife, or a red powder. I would go for it being Non Metallic.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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Ivor and Olive Lewis on tue 15 apr 08
Dear Duff bogen=20
You ask <<....As I put my lip to a new cup, the thought arose "Is this =
safe?" and I couldn't answer myself with 100% satisfaction. The slip is =
~90% a high iron lateritic clay-soil and ~10% MnO2. It fuses at ^6 but I =
wonder about Mn leechinig out and its toxicity.
What are your impressions of this situation?...>>
Sorry, but there is insufficient information for me to give an firm =
answer. The only sure way to know is to send a sample to a Lab and have =
it tested form Manganese release.
I suppose the hidden question is "Do salivary secretions dissolve =
pottery glazes" . Since they are neutral or slightly alkali so the =
enzymes that break down Starch can work it seems plausible that they do =
not.
Interesting problem though ! ! !
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Ron Roy on sun 20 apr 08
Hi Duff,
I really don't think there is a danger but there was a study recently of
children in Bangladesh. The water they have to drink is contaminated with
Manganese and they have similar symptoms to lead posioning.
Do you have glaze over the slip?
The regulations for lead and candmium say you have to keep the glaze a
certain distance below the rim of a cup - so lips cannot touch the glaze.
RR
>Ivor et al.
> As I put my lip to a new cup, the thought arose "Is this safe?" and I
>couldn't answer myself with 100% satisfaction. The slip is ~90% a high
>iron lateritic clay-soil and ~10% MnO2. It fuses at ^6 but I wonder about
>Mn leechinig out and its toxicity.
> What are your impressions of this situation?
> DRB
> Seattle
>
>Ivor and Olive Lewis wrote:
> Dear John Sankey,
>
><<"phosphorus [is] normally an insoluble non-conductor"
>
>Elemental phosphorus is a metal, conductivity 10 milliohm-cm. For
>comparison: iron (again, elemental) is 9.7, magnesium 4.4>>
>
>I am not sure which definitions of Metal and Non Metal you are using.
>Since there is a clear conflict here, perhaps you would provide
>definitions.
>
>Phosphorus is not listed by Kaye and Laby,"Tables of Physical and Chemical
>Constants", in their table of Resistivities of Metallic Elements, PP
>102-3,
>
>My experience of handling Phosphorus is that it is a Semi Transparent
>Yellow Wax like substance that stored under water and is easily cut with
>the blade of a knife, or a red powder. I would go for it being Non
>Metallic.
>
>Best regards,
>
>Ivor Lewis.
>Redhill,
>South Australia.
>
>______________________________________________________________________________
>Clayart members may send postings to: clayart@lsv.ceramics.org
>
>You may look at the archives for the list, post messages, change your
>subscription settings or unsubscribe/leave the list here:
>http://www.acers.org/cic/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
>
>______________________________________________________________________________
>Clayart members may send postings to: clayart@lsv.ceramics.org
>
>You may look at the archives for the list, post messages, change your
>subscription settings or unsubscribe/leave the list here:
>http://www.acers.org/cic/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
Ron Roy
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Des & Jan Howard on mon 21 apr 08
Ron
One of our local towns has a manganese problem with its water.
So much so that snots of manganese stains clothes in washing machines.
No reports of anything but householder annoyance have been heard.
One thing I learned in nursing was that contamination
does not equal infection.
Des
Ron Roy wrote:
>
> I really don't think there is a danger but there was a study recently of
> children in Bangladesh. The water they have to drink is contaminated with
> Manganese and they have similar symptoms to lead posioning.
>
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