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: flowers of clay & toxicity question

updated tue 23 sep 03


Laurie Kneppel on fri 19 sep 03

Interesting question about the dental alginate. I used to do a lot of
theater makeup and cast a lot of peoples' faces with it to make
prosthetics out of foam latex. (now I use their lifecasts as bases for
masks made of clay) I know alginate is derived from seaweed somehow and
I know dental alginate is made from food grade materials, but it is
also contains silica and is considered hazardous in its powder form
because of that. Alginate shrinks like crazy once the water evaporates
back out, but when you do face casts you can get some really cool
shrunken heads if you stick a paper towel in the cast and try to help
the alginate shrink somewhat proportionally! I wouldn't leave it on
anything delicate or it could squish it or fracture it. But I would
guess if you poured slip into the alginate right away it would probably
deform the slipcast object because the water in the slip wouldn't have
any place to evaporate out to since the alginate is really mostly water
at that point. Then again, I haven't worked with casting slip very much
so i don't know how it behaves in non-porous molds. But the alginate
eventually dries and you can crush it back into chunks and powder, but
you can't use it again except maybe to add texture to a surface or
something. I wonder if it has enough silica in it to do anything
interesting if it was fired? Hmmm, I'll have to see if I have any old
alginate stashed away in the closet and do an experiment! If I were
casting something delicate using alginate, i wouldn't pour slip into
it. I would pour plaster into it and make a multi-part plaster mold off
of the plaster cast. It's not as spontaneous, but you should be able to
get a nice cast out of it. And you could use it over and over until the
mold broke.

And Newbies - I don't care what you do with clay, as long as you are
"doing something" with clay! It's like playing a musical instrument,
whether you use it for Haydn or hip-hop, at least you are still playing
something and using a part of your brain that usually just sits there
neglected. There's too great a lack of exposure to art and music in our
schools and our society these days to exclude anyone who is actively
pursuing any size interest in these areas. But that's just my opinion.
I personally "push" art and music at anyone who will listen to me.

Cheers from sunny Sacramento,

On Friday, September 19, 2003, at 10:58 AM, ccpottery@BELLSOUTH.NET

> Carole -
> To capture delicate objects and fine details, I use liquid latex.
> You can dip the face of the flower to capture the texture ...
> then let it hang upside down
> to dry ... then dip it again. Use another similar flower to capture
> the textures on the back
> of the flower.
> I have dipped whole objects in ordinary slip, then fired it with
> great results. Can be
> quite delicate ... depends on how many layers of slip, how thick ...
> etc
> NOW ... I have no personal experience with this but ..... I have
> heard discussions
> where potters obtained the stuff dentists use to make impressions of
> teeth and had
> success molding objects with it. You have to use the resulting mold
> right away because
> this stuff shrinks like crazy overnight. But they say the detail is
> amazing.
> Does anyone out there know if it would just burn away in the kiln
> leaving the pottery
> flower behind?? Is is toxic as it burns?
> Chris Campbell - in North Carolina - safe and sound ... branches all
> over the yard, but no
> trees down. Funny quote from a columnist in our paper ...' Waiting for
> a hurricane is like
> having company coming next week who call you every ten minutes to let
> you know they
> are still on their way ... and bringing the family dog who is ill'
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Snail Scott on mon 22 sep 03

At 01:58 PM 9/19/03 -0400, you wrote:
>... I have heard discussions
>where potters obtained the stuff dentists use to make impressions of teeth
and had
>success molding objects with it...
> Does anyone out there know if it would just burn away in the kiln
leaving the pottery
>flower behind?? Is is toxic as it burns?

Dental alginate is mostly water in its mixed-up
form. Because of this, you can't slip-cast
directly into it - the slip would never set up.
It's also too soft to work well for press-
molding. It COULD be used to make a hydrocal
duplicate of the flower (if the flower were
thick enough), which could then be used as the
pattern for a plaster slip-casting mold.

Alginate is non-toxic and organic, though, so
if there were any reason to put some in a kiln,
I think it would burn away without much fume or