John Hesselberth on wed 1 feb 06
On Feb 1, 2006, at 10:50 AM, Mark Tigges wrote:
> Is my fogginess this
> morning due to the three pints I had last night? Or is it the mug?
Hi Mark,
I'd place my money on the 3 pints. I don't have my Sax Dictionary of
Dangerous Materials with me, but Mn is not particularly toxic by
ingestion. In fact you will find MnO2 in most every vitamin tablet.
It is the fumes and/or dust that are particularly dangerous. Not that
you want to ingest large quantities, though. What you may find is
that the mugs lose their beautiful surface from the Manganese or
other colorants leaching out of them after a while. Any surface or
glaze that is loaded with extra colorant is not really suitable for
functional work. It may or may not be dangerous depending on what the
colorants are, but it will almost certainly not be very durable.
Regards,
John
Mark Tigges on wed 1 feb 06
The recent discussion on lead, and a recent development in my glazing
has led me to wonder something. Are there other problematic
oxides/metals whose vapours can cause problems?
I have been getting some asolutely beautiful results combining the
glazes from M^6G with the black stain from the CM article by Richard
Busch titled "A wood fired look from an eletric kiln" which appeared
in Feb '03. It was later included in the article that appeared in PMI
late last year.
This stain includes a whos who of the enememies. Chiefly, manganese.
Now, I use manganese in one of my main glazes from M^6G, and I am aware
of the problems that it can cause (impotence ... yikes! oh, and
dementia ... eh, half way there naturally). I am quite careful
handling the raw material. Because I have decided to
trust the authors of the book, I do not verify their results that the
manganese does not cause any problem in the finished piece.
But, now I find myself using copious amounts of this manganese based
stain over top glazes. I am curious if the metals and oxides in this
stain are contaminating the atmosphere in my kiln with excess vapour,
and further if that vapour is being condensed onto the finished ware.
I do not use this stain inside functional pieces, but if the nasties
are being condensed onto (and into) the glazed surface could there be a
lasting problem with the ware?
I'm currently sipping coffee from the most beautiful mug I have ever
made, thanks in large part to this stain. Is my fogginess this
morning due to the three pints I had last night? Or is it the mug?
Any opinions?
Mark.
Ivor and Olive Lewis on thu 2 feb 06
Dear Mark Tigges,
This is a very serious question. It can only be resolved by thorough =
research. There is both anecdotal and scientific evidence out there but =
be cautious about information on the WWW. Always crosscheck with Hard =
Copy. If possible find authorities outside Studio Pottery and Ceramic =
Arts to verify information.
My suggestion is to treat materials known to cause problems, if =
ingested, with absolute respect.
I also think it is important for those who tell us that certain =
elements will be leached from a glaze by food or beverage acids explain =
the chemistry. Just to say that acids dissolve the materials from the =
glaze is not sufficient. We need to know why chemical reactions that =
would sequester them in a glaze do not happen. For example, Zinc in =
excess in a silicate glaze forms those wonderful crystals yet Copper =
which can have similar electron affinities does not and is leached from =
a glaze. Why should this happen? Zinc oxide reacts with acids.
Keep asking questions.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Ron Roy on fri 3 feb 06
Hi Mark,
You have much good advice so far - - manganese dust and fumes are to be
avoided at all cost - run away!
I see in Manona's news letter that the welders claim of damage from
manganese has been upheld in court - must mean something.
You answers are in her book - which are dangerous, which are suspected
dangerous and which are safe - which way of entry is a probem - all there
when ever you have a question.
The Artists Compleat Health and Safety Guide - Monona Rossol.
RR
>But, now I find myself using copious amounts of this manganese based
>stain over top glazes. I am curious if the metals and oxides in this
>stain are contaminating the atmosphere in my kiln with excess vapour,
>and further if that vapour is being condensed onto the finished ware.
>I do not use this stain inside functional pieces, but if the nasties
>are being condensed onto (and into) the glazed surface could there be a
>lasting problem with the ware?
>
>I'm currently sipping coffee from the most beautiful mug I have ever
>made, thanks in large part to this stain. Is my fogginess this
>morning due to the three pints I had last night? Or is it the mug?
>
>Any opinions?
>
>Mark.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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