David Hendley on tue 18 sep 01
Hi Ron. I thought the ever-vigilant Clayart 'durable glaze police'
might pull me over for this.
The 'casting slip' suggestion is not a 'glaze'. It is a semi-glossy
slip-glaze that is used like a slip, i.e., brushed on the outside of
pots for color and decoration.
It was offered in response to a query about how to paint over a
leaf impressed in clay and have a glaze-like surface around the
impression, without the need to apply a clear glaze later.
It is an easy and reliable cone 10 slip I've used for years. It never
crawls, pinholes, or flakes off, much less causes pots to break.
With 90% of the flux coming from magnesium, it's molecular
formula falls way out of the boundaries of common limit formulae.
But it works for this purpose. It is not a 'liner glaze'.
I use glaze calculation and limit formulae regularly, but
when faced with a recipe that works and some numbers that
say it will not work, I'll take reality, not theory.
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com
----- Original Message -----
From: "Ron Roy"
To:
Sent: Sunday, September 16, 2001 11:48 PM
Subject: Re: slip or glaze? WAIT! this could be a disaster
> One way of making very low expansion glazes is to use MgO as the main
flux.
>
> This "C10" glaze would have a very low expansion rate - a pot buster for
> sure - try it as a liner glaze and tell us what happened.
>
> If it was used as a vitrious slip at cone 6 I would expect the same kind
of
> result.
>
> I hate to contradict DH - he is such a wonderful person but I am counting
> on his good nature to take this in the spirit it is given.
>
> RR
>
>
> >An easy way to try using a slip-glaze is to buy (or make) some
> >low-fire white casting slip. The typical recipe for such slips
> >is 50% talc and 50% ball clay, plus a defloculant. At cone 10
> >this slip will make a white low silica matt glaze. Add oxides to
> >make colors; cobalt will produce purple because of the massive
> >amount of magnesium in the slip.
Ron Roy on wed 19 sep 01
Dear David,
Ha! this is making me think again - that slip should be full of
cristobalite - which may offset the low expansion - make me a couple of dil
rods and we will find out why it's not shivering off your pots
Goody - a chance to add to the collective knowledge.
"I don't need no stinking badge" - RR
Revised quote from the film Treasure of the Sieara Madre.
>Hi Ron. I thought the ever-vigilant Clayart 'durable glaze police'
>might pull me over for this.
>The 'casting slip' suggestion is not a 'glaze'. It is a semi-glossy
>slip-glaze that is used like a slip, i.e., brushed on the outside of
>pots for color and decoration.
>It was offered in response to a query about how to paint over a
>leaf impressed in clay and have a glaze-like surface around the
>impression, without the need to apply a clear glaze later.
>
>It is an easy and reliable cone 10 slip I've used for years. It never
>crawls, pinholes, or flakes off, much less causes pots to break.
>With 90% of the flux coming from magnesium, it's molecular
>formula falls way out of the boundaries of common limit formulae.
>But it works for this purpose. It is not a 'liner glaze'.
>I use glaze calculation and limit formulae regularly, but
>when faced with a recipe that works and some numbers that
>say it will not work, I'll take reality, not theory.
>
>David Hendley
>Maydelle, Texas
>hendley@tyler.net
>http://www.farmpots.com
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
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