wayneinkeywest on mon 13 oct 03
Ohmigoodness. In that case I'm schkrewed! (Sorry Ms Lili!)
With all the calcium and the lime in our water (even filtered
city water) I may not be making pots, I may be making
bombs! Isn't lime supposed to pop out at inopportune
moments...like when a customer gets a pot home
and sets it on a shelf to admire it...ping!
Rain water? Wouldn't touch the stuff around here. Kills plants.
Too much salt (ocean gets picked up in storms as pass through)
Sheesh!
Wayne in Key West
> And last: Experts, please opine. One of my favorite theories is that
when
> we use reclaimed clay over and over and over again, or buy clay bodies, we
> are ALSO getting and "reinforcing" stuff that may be in the water...In
other
> words we import the materials in the water we get in the clay body, and we
> get more as we reclaim clay. (I am lucky and use rain water) Could that
> affect a clay body's effect on glaze after a year or so?
>
> Lili Krakowski
> Constableville, N.Y.
Lily Krakowski on mon 13 oct 03
Barbara: I know you have thought of all the obvious problems/solutions.
That several of your raw materials, being mined, being then from different
mine runs, have changed. Recalculation may help. Wollastonite may work
instead whiting, and so on. I am surprised you still can get a
lead-containing frit, but, I gather, from what I read recently ON Clayart,
frit formulations have been changed over the years, so theoretically, the
3304 you had then is not the one you have now.
Have you tried your glaze with distilled water? That would "report" if it
is the water change. I also would suggest that you test the glaze over a
white slip--the simpler the better, just ball clay and kaolin maybe.
And again I suggest as always that you get 25 lbs of different clay bodies
for your firing temperature and test that glaze on a tile of each.
And last: Experts, please opine. One of my favorite theories is that when
we use reclaimed clay over and over and over again, or buy clay bodies, we
are ALSO getting and "reinforcing" stuff that may be in the water...In other
words we import the materials in the water we get in the clay body, and we
get more as we reclaim clay. (I am lucky and use rain water) Could that
affect a clay body's effect on glaze after a year or so?
Lili Krakowski
Constableville, N.Y.
Be of good courage....
Malcolm Schosha on tue 14 oct 03
Wayne,
I seem to recall you saying that you are making porcelain. Calcium
is a high temp. flux., and would not be a problem (as far as I know)
in porcelain.
Malcolm
--- In clayart@yahoogroups.com, wayneinkeywest
wrote:
> Ohmigoodness. In that case I'm schkrewed! (Sorry Ms Lili!)
> With all the calcium and the lime in our water (even filtered
> city water) I may not be making pots, I may be making
> bombs! Isn't lime supposed to pop out at inopportune
> moments...like when a customer gets a pot home
> and sets it on a shelf to admire it...ping!
> Rain water? Wouldn't touch the stuff around here. Kills plants.
> Too much salt (ocean gets picked up in storms as pass through)
> Sheesh!
> Wayne in Key West
>
> > And last: Experts, please opine. One of my favorite theories is
that
> when
> > we use reclaimed clay over and over and over again, or buy clay
bodies, we
> > are ALSO getting and "reinforcing" stuff that may be in the
water...In
> other
> > words we import the materials in the water we get in the clay
body, and we
> > get more as we reclaim clay. (I am lucky and use rain water)
Could that
> > affect a clay body's effect on glaze after a year or so?
> >
> > Lili Krakowski
> > Constableville, N.Y.
>
>
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Snail Scott on tue 14 oct 03
At 09:36 PM 10/13/03 -0400, you wrote:
>With all the calcium and the lime in our water (even filtered
>city water) I may not be making pots, I may be making
>bombs! Isn't lime supposed to pop out at inopportune
>moments...
No, not at all! Lime is calcium, after all - a flux.
The particles found in water are about as tiny as it
gets; they just dissolve in the melt. It's LARGE
bits that cause lime pop - bits too large to melt
into the clay around them. How big is 'too big'
depends on your firing temperature. At ^10 even
pea-sized chunks will melt, and maybe just leave
melted holes where they were, while at earthenware
temperatures, a pinhead-sized bit won't really melt
at all. That's why lime pop is mainly associated with
low-fire clay, and with bisqued clay sitting around
awaiting a higher firing. The low firing just
calcines the lime, and when it rehydrates due to
ambient humidity (or washing) it expands, causing
any bits near the surface to blow out the covering
clay. If you look at cheap terra-cotta flowerpots,
you will often see these little blowouts, with a
bit of white stuff still at the bottom of the divot.
-Snail
wayneinkeywest on tue 14 oct 03
Damn! And here I thought I was gonna have a good chance to wake up the
neighborhood .
Thank you Ms Snail.
Wayne
> At 09:36 PM 10/13/03 -0400, you wrote:
> >With all the calcium and the lime in our water (even filtered
> >city water) I may not be making pots, I may be making
> >bombs! Isn't lime supposed to pop out at inopportune
> >moments...
>
>
> No, not at all! Lime is calcium, after all - a flux.
> The particles found in water are about as tiny as it
> gets; they just dissolve in the melt. It's LARGE
> bits that cause lime pop - bits too large to melt
> into the clay around them. How big is 'too big'
> depends on your firing temperature. At ^10 even
> pea-sized chunks will melt, and maybe just leave
> melted holes where they were, while at earthenware
> temperatures, a pinhead-sized bit won't really melt
> at all. That's why lime pop is mainly associated with
> low-fire clay, and with bisqued clay sitting around
> awaiting a higher firing. The low firing just
> calcines the lime, and when it rehydrates due to
> ambient humidity (or washing) it expands, causing
> any bits near the surface to blow out the covering
> clay. If you look at cheap terra-cotta flowerpots,
> you will often see these little blowouts, with a
> bit of white stuff still at the bottom of the divot.
>
> -Snail
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Louis Katz on tue 14 oct 03
Pea sized pieces of hi purity lime don't melt at cone ten. But you are
right the lime in the water is not a problem in this regard. Most clays
have some lime no, just not chunks?
Pea size chunks still cause lime blows, it just takes longer for the
water to get through the vitreous clay.
Lime Melting Point 2572 C
Lime does melt in contact with clay but this is usually limited to a
very thin skin.
More on lime in water, glazes, plaster:
http://falcon.tamucc.edu/~lkatz/articles/calcia.html
Louis
> At ^10 even
> pea-sized chunks will melt, and maybe just leave
> melted holes where they were, w
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