iandol on wed 4 apr 01
Although the elemental oxide analysis of Portland or other hydraulic =
cement may enable calculations to be made so that it can be incorporated =
into glaze recipes I see a distinct disadvantage in using it. It is =
Hydraulic. It sets up because a portion of the minerals which form =
during calcination dissolve in water and cause rapid crystal growth. I =
believe cement is never fused or melted in the same way that a frit is. =
It is sintered to a clinker, then ground to an impalpable powder. The =
raw materials are limestone and clay though in modern production fly =
ash, the residues from burning solid fossil fuel, are also incorporated =
into the raw materials. Anyone with access to a coal burning power =
station may wish to consider Fly Ash as a potential glaze ingredient.
Best regards,
Ivor Lewis. Redhill, South Australia
Ababi on thu 5 apr 01
Hello Ivor.
I am a very curious person that is why I try to make glazes with different
materials than I can buy from my supplier like: SiC Portland cement the bad
soil (for agriculture) out of my studio, perlite, vermiculite desert colored
rocks ETC.
The oxide analyses of the cement is only a guide in the calculating. I would
not use it as a regular base, as it is a terrible to keep and ruining your
tools, if you do not wash them immediately not to talk about irritating your
skin.
I tried to use coal ash. My teacher brought some, from road that was built
near her home, it was not dust, I had to clean and shieve it.
I used an analysis I got fro a ClayArter I believe from Phill Rogers's Ash
glazes book.
COAL ASH.
================
CaO 0.43* 4.08%
MgO 0.52* 3.50%
TiO2 0.09 1.17%
Al2O3 1.91 32.64%
P2O5 0.05* 1.17%
SiO2 4.72 47.55%
Fe2O3 0.37 9.91%
Si:Al 2.47
SiB:Al 2.47
Expan 5.82
I tried to get better analysis to our local Coal ash and could not, as it
was imported from all around the world.
I was told that I could buy in low cost, "a few tons"of the coal dust.
I made a glaze using Insight, took the Hansen's 20/5 changing materials.got
a nice glaze nothing special.What I was looking for was a substitute to
volcanic ash and it was not.
The main reason for not going on, in this material, was that I could not
know about heavy metals that could be there.
Ababi Sharon
ababisha@shoval.ardom.co.il
http://members4.clubphoto.com/ababi306910/
----- Original Message -----
From: "iandol"
To:
Sent: Wednesday, April 04, 2001 8:28 AM
Subject: Cement in Glazes. also Fly Ash.
Although the elemental oxide analysis of Portland or other hydraulic cement
may enable calculations to be made so that it can be incorporated into glaze
recipes I see a distinct disadvantage in using it. It is Hydraulic. It sets
up because a portion of the minerals which form during calculation dissolve
in water and cause rapid crystal growth. I believe cement is never fused or
melted in the same way that a frit is. It is sintered to a clinker, then
ground to an impalpable powder. The raw materials are limestone and clay
though in modern production fly ash, the residues from burning solid fossil
fuel, are also incorporated into the raw materials. Anyone with access to a
coal burning power station may wish to consider Fly Ash as a potential glaze
ingredient.
Best regards,
Ivor Lewis. Redhill, South Australia
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