Lisa Wiese on mon 14 aug 06
Greetings to all,
Thanks for those of you who responded to my Alfred Analytical Lab question.
And Paul, I will be using ALS Chemex...thanks. The minimum is now $150.00...
a little steep but I can get six whole rock analysis tests for that.
My question...
I am wanting to use limestone from my property for the calcium carbonate in
my glazes. Since I don't have a rock crusher, the only way I can break down
the limestone into a managable mesh size for the ball mill is to heat it
up...then of course it turns to quicklime. I have been rehydrating it and
then drying it out again into powder form before I use it in a glaze. I'm
not sure that I'm doing the right thing by heating up the limestone at all.
Does anyone know if I can manipulate limestone this way or am I turning it
into something that might cause me trouble down the road as the glaze sits
in a bucket...I do know that quicklime is caustic, but as it rehydrates it
just turns back into calcium carbonate...right?
Just don't want to stick my hand in the glaze slurry 6 months down the road
and pull up a handless arm...
I did run a glaze test with the rehydrated quicklime/CaO and the glaze
looked pretty much like the original.
Any feedback is appreciated!!!
Lisa
Paul Herman on mon 14 aug 06
Lisa,
I found out the local limestone (tufa) is really hard to crush, so
can relate. Wood ashes are a great source of calcium.
If your limestone is fired hot enough to drive off the carbon,
hydrating the lime will not turn it back into CaCO3. I think it would
be "hydrated lime", and would be caustic.
No carbon is added by water. So this glaze might be one you don't
want to stir with your hands.
An interesting fact is that almost all of the earth's carbon is
locked up in carbonate rocks, limestone and dolomite, etc.
Best,
Paul Herman
Great Basin Pottery
Doyle, California US
http://greatbasinpottery.com
On Aug 14, 2006, at 1:04 PM, Lisa Wiese wrote:
> I do know that quicklime is caustic, but as it rehydrates it
> just turns back into calcium carbonate...right?
>
>
Joseph Herbert on tue 15 aug 06
Lisa Wiese wrote: "I do know that quicklime is caustic, but as it rehydrates
it just turns back into calcium carbonate...right?"
No, What is lost upon heating is CO2, not water. Putting CaO in water makes
a caustic solution, not anything like a slurry calcium carbonate in water.
CaO in water then has the disadvantages of other soluble glaze materials,
penetrating the porous body, selective removal with water, as well as the
caustic problem.
Ivor suggested a short piece of large diameter pipe welded to a base plate
as an iron mortar. Repeated vertical applications of a 4 foot piece of 1
inch rebar into rocks in the mortar should yield ball millable size pieces.
Heating below red heat and plunging into water (an exciting prospect) could
reduce the limestone to smaller pieces without driving off too much CO2.
Hammers in the greater than four pound range will also reduce the size of
rocks.
If the limestone of your yard and dreams is used as road metal or aggregate
in the local area, a visit to the crushing / screening plant to collect
washed off fine fractions might get you your limestone dust with a lot less
work. Some places in Kansas you could just offer to wash three farm
vehicles. Collecting the residue of the washing would yield a couple kilos
of limestone dust.
Proceed with caution,
Joseph Herbert
Ivor and Olive Lewis on tue 15 aug 06
Dear Lisa Wiese,=20
Your suppositions are correct. Limestone is converted to Calcium Oxide =
above about 850 deg Celsius. Carbon dioxide is driven off leaving a =
residue of Calcium Oxide. Calcium oxide is slightly soluble in water =
with which it forms Calcium Hydroxide. This is the"Lime Water" used to =
detect the presence of Carbon dioxide in a gas stream. Calcium Carbonate =
is thrown out of solution as a white precipitate.
A quicker way would be to either purchase or have made a Geologists =
"Dolly Pot", a portable device for reducing small samples to an =
impalpable powder. Ten minutes and a half pound sample can be reduced to =
a useable minus 100 mesh. I'm sure you would find illustrations on the =
web.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Lee Love on wed 16 aug 06
Several folks on ClayCraft and Woodkiln lists have bought
smallhandmills from Big Sky Machine Co. for crushing stone.
Their website no longer works but you could try writing:
ben@bigskymachine.com'
You can see the old webpages at the Wayback Machine:
http://web.archive.org/web/20050305095722/http://www.bigskymachine.com/
--
Lee in Mashiko, Japan
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi
Hank Murrow on wed 16 aug 06
On Aug 16, 2006, at 12:28 AM, Lee Love wrote:
> Several folks on ClayCraft and Woodkiln lists have bought
> smallhandmills from Big Sky Machine Co. for crushing stone.
>
> Their website no longer works but you could try writing:
>
> ben@bigskymachine.com'
>
Looks like they are kaput, Lee. An email message came back
'undeliverable'.
Cheers, Hank
www.murrow.biz/hank
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