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glaze without feldspar

updated mon 19 oct 98

 

Reid Harvey on thu 15 oct 98

Greetings from the Ivory Coast. A group of us here are working to
maximize use of local materials for clay bodies and glazes.
Unfortunately, ceramists must import feldspar, at high cost, in order to
make glazes, a big impediment to startup. (Note: Please don't tell me
that feldspars are common. This is not as true in tropical latitudes as
it is elsewhere.)

We will be working on frit production, using triaxial blends, and
appropriate materials: sand and kaolin, as well as some combination of
network modifiers. Typically available for other industrial uses, these
include compounds of boron, sodium, potassium and calcium. We have some
pretty good ideas as to how to go about this. But can I try something a
little different?

What if I use a glassy, low fire body, fired to maturity, then glazed
for a second firing? This would eliminate the problem of movement of
soluble salts. If this idea isn't to far out, could I get control over
the amount of glaze applied? With conventional water based glaze over a
porous body I would work towards a thickenss of two or three sheets of
paper. Could I approximate this by using some viscous medium for
combination with the glaze? Or perhaps some kind of adhesive. The catch
is we must avoid imports.

Thanks for any constructive thoughts.
Reid Harvey

Grimmer on sat 17 oct 98

Reid,
Wow, Ivory Coast. Cool.
If you have high fire capabilities (kilns and clay body) and access to
local red clay, you are in the zone. For a feldspar-free glaze, start with
the red clay and progressively add alkaline earths (whiting, dolomite or
limestone, wollastonite, wood ash, strontium carbonate are good sources)
and flint until you get your lovely, brown (or black) glaze. Some great
pottery from all over the world has used this very combination. With
Insight, I see that 80 %Redart (common US red clay) forms what looks like a
balanced cone 10 glaze with 12 whiting, 5 dolomite, and 3 flint. Haven't
tested it.

Untitled Recipe 2
=================
REDART.............. 80.00 80.00%
WHITING............. 12.00 12.00%
FLINT............... 3.20 3.20%
DOLOMITE............ 4.80 4.80%
========
100.00

CaO 0.61* 9.62%
MgO 0.23* 2.63%
K2O 0.14* 3.75%
Na2O 0.02* 0.34%
TiO2 0.04 0.99%
Al2O3 0.49 14.02%
P2O5 0.00 0.19%
SiO2 3.66 62.08%
Fe2O3 0.14 6.38%

Cost/kg 0.24
Si:Al 7.52
SiB:Al 7.52
Expan 6.86

Too much alkaline earth and too little silica will give you a fake-ash
glaze, which depending on your tastes, may or may not be a good thing.

Good Luck.

steve grimmer
marion illinois

----------
>From: Reid Harvey
>To: CLAYART@LSV.UKY.EDU
>Subject: Glaze without feldspar
>Date: Thu, Oct 15, 1998, 8:51 AM
>

>----------------------------Original message----------------------------
>Greetings from the Ivory Coast. A group of us here are working to
>maximize use of local materials for clay bodies and glazes.
>Unfortunately, ceramists must import feldspar, at high cost, in order to
>make glazes, a big impediment to startup. (Note: Please don't tell me
>that feldspars are common. This is not as true in tropical latitudes as
>it is elsewhere.)
>
>We will be working on frit production, using triaxial blends, and
>appropriate materials: sand and kaolin, as well as some combination of
>network modifiers. Typically available for other industrial uses, these
>include compounds of boron, sodium, potassium and calcium. We have some
>pretty good ideas as to how to go about this. But can I try something a
>little different?
>
>What if I use a glassy, low fire body, fired to maturity, then glazed
>for a second firing? This would eliminate the problem of movement of
>soluble salts. If this idea isn't to far out, could I get control over
>the amount of glaze applied? With conventional water based glaze over a
>porous body I would work towards a thickenss of two or three sheets of
>paper. Could I approximate this by using some viscous medium for
>combination with the glaze? Or perhaps some kind of adhesive. The catch
>is we must avoid imports.
>
>Thanks for any constructive thoughts.
>Reid Harvey

Amiram Khen on sat 17 oct 98

Hi Harvey,
I hope the following two suggestions may be of use:
1. Wood ashes can be used to replace most or all of the feldspars. You have
to experiment with the ashes
and other materials available to you.
2. If your kiln is not an electric one, try salt or soda glazing.

Amiram


Reid Harvey wrote:

> ----------------------------Original message----------------------------
> Greetings from the Ivory Coast. A group of us here are working to
> maximize use of local materials for clay bodies and glazes.
> Unfortunately, ceramists must import feldspar, at high cost, in order to
> make glazes, a big impediment to startup. (Note: Please don't tell me
> that feldspars are common. This is not as true in tropical latitudes as
> it is elsewhere.)
>
> We will be working on frit production, using triaxial blends, and
> appropriate materials: sand and kaolin, as well as some combination of
> network modifiers. Typically available for other industrial uses, these
> include compounds of boron, sodium, potassium and calcium. We have some
> pretty good ideas as to how to go about this. But can I try something a
> little different?
>
> What if I use a glassy, low fire body, fired to maturity, then glazed
> for a second firing? This would eliminate the problem of movement of
> soluble salts. If this idea isn't to far out, could I get control over
> the amount of glaze applied? With conventional water based glaze over a
> porous body I would work towards a thickenss of two or three sheets of
> paper. Could I approximate this by using some viscous medium for
> combination with the glaze? Or perhaps some kind of adhesive. The catch
> is we must avoid imports.
>
> Thanks for any constructive thoughts.
> Reid Harvey

David Hendley on sun 18 oct 98


Glass cullet comes to mind.
I don't know if glass bottles and jars are readily available in Ivory Coast,
but it is a ready-made frit - If you add kaolin at the right proportion
you will have a direct substitute for feldspar that is not water-soluble.

Wood ash?
A good flux for stoneware, but soluble and inconsistent.

Red clay?
Most red clays will make a dark colored glaze at stoneware temps
with only slight modifications. Albany slip is the most well-known.


Good luck with your project.
David Hendley
Maydelle, Texas



At 09:51 AM 10/15/98 EDT, you wrote:
>----------------------------Original message----------------------------
>Greetings from the Ivory Coast. A group of us here are working to
>maximize use of local materials for clay bodies and glazes.
>Unfortunately, ceramists must import feldspar, at high cost, in order to
>make glazes, a big impediment to startup. (Note: Please don't tell me
>that feldspars are common. This is not as true in tropical latitudes as
>it is elsewhere.)
>
>We will be working on frit production, using triaxial blends, and
>appropriate materials: sand and kaolin, as well as some combination of
>network modifiers. Typically available for other industrial uses, these
>include compounds of boron, sodium, potassium and calcium. We have some
>pretty good ideas as to how to go about this. But can I try something a
>little different?
>
>What if I use a glassy, low fire body, fired to maturity, then glazed
>for a second firing? This would eliminate the problem of movement of
>soluble salts. If this idea isn't to far out, could I get control over
>the amount of glaze applied? With conventional water based glaze over a
>porous body I would work towards a thickenss of two or three sheets of
>paper. Could I approximate this by using some viscous medium for
>combination with the glaze? Or perhaps some kind of adhesive. The catch
>is we must avoid imports.
>
>Thanks for any constructive thoughts.
>Reid Harvey
>