[Clayart] Wollastonite/hardening clay bodies

Bryan Johnson bryj at cheqnet.net
Wed Jul 19 21:14:03 EDT 2017


I remember seeing work being done on a 50 : 50 ball clay wollastonite
body.  They were making very large panels that were somewhat flexible.

Bryan Johnson

On Wed, Jul 19, 2017 at 6:40 PM, Paul Gerhold <gerholdclay at gmail.com> wrote:

> Well the opinion I stated on Wollastonite comes from Jon Pacini at Laguna
> who probably has an inarguable knowledge of clay ingredients.  My
> experience just confirms what he said about Wollastonite causing clay to
> harden in the bag while not actually contributing any particular benefit to
> the body.  Opinions may differ but his has proven out in my experience.
>
> Paul
>
> Sent from my iPad
>
> > On Jul 18, 2017, at 5:22 PM, David Woof <woofpots at hotmail.com> wrote:
> >
> > Paul,
> >
> > our experience is obviously different, of course there are many
> variables related to the other mineral constituents when combined in a
> particular clay body formula and the water one used as well.
> >
> > So before laying too much pro or con at the feet of wollastonite........
> we must tread softly....yet push ahead in our quest for Ceramic knowledge.
> >
> >
> > I had hoped to stimulate thought and possible conversation re the last
> paragraph of my post:
> >> Wollastonite offers much more to a clay body or glaze than simply as a
> convenient source of, or substitution for, calcium and silica. ***It's
> aricular structural character provides a dimensional stability and flexural
> modulus to the materials it is added to.****  It is not >difficult to
> translate this to beneficial reasons for application in our glazes and clay
> bodies, before, during, and post firing.
> >
> >
> > However; since many folks now buy ready made box clays, subsequently
> don't much care what is in the clay as long as it works the way they like
> it or willing to suffer through with it, and us few who know our materials
> and formulate accordingly, there is probably scant interest in conversation
> about what we think we already know!!!!    So Tally-Ho Mates!!! the fox is
> hiding in the hen house, licking his flexural modulus, and yawning his fox
> in the hen house grin.
> >
> > Misneach,
> >
> > David
> >
> > ***************************************************************
> >
> > ________________________________
> > From: Clayart <clayart-bounces at lists.clayartworld.com> on behalf of
> Paul Gerhold <gerholdclay at gmail.com>
> > Sent: Friday, July 7, 2017 2:46 PM
> > To: Clayart international pottery discussion forum
> > Subject: Re: [Clayart] Wollastonite/hardening clay bodies
> >
> > That may well be but when I eliminated the 5% wollastonite from my clay
> body, as recommended from a post asking for  help on Clayart, the body
> stopped becoming hard after a few months in storage with no discernible
> change in throwing properties and no change in raw or fired strength.
> >
> > And the body was mixed very soft in an attempt to overcome the
> hardening. That did not work.
> >
> > Paul
> >
> >
> > Sent from my iPad
> >
> >> On Jul 6, 2017, at 3:40 PM, David Woof <woofpots at hotmail.com> wrote:
> >>
> >> Wollastonite is a valuable material, though still often under rated and
> misunderstood.  What is needed is a working understanding of the mineral
> composition and characteristics of raw materials useful in ceramics.,m
> >>
> >>
> >> Wollastonite is a hygroscopic material and so absorbs water, other
> materials including clays such as Hawthorne Clay and grog also absorb
> significant quantities of water during post mixing of the clay body. The
> simple trick is to pug it wetter than useful and "age" while the absorption
> reaches stasis.
> >>
> >>
> >> Wollastonite offers much more to a clay body or glaze than simply as a
> convenient source of, or substitution for, calcium and silica. It's
> aricular structural character provides a dimensional stability and flexural
> modulus to the materials it is added to.  It is not difficult to translate
> this to beneficial reasons for application in our glazes and clay bodies,
> before, during, and post firing.
> >>
> >>
> >> Woof
> >>
> >>
> >>
> >>
> >>
> >> ________________________________
> >> From: Clayart <clayart-bounces at lists.clayartworld.com> on behalf of
> Paul Gerhold <gerholdclay at gmail.com>
> >> Sent: Wednesday, May 10, 2017 7:12 AM
> >> To: Clayart international pottery discussion forum
> >> Subject: [Clayart] Hardening Clay
> >>
> >> Back about ten years ago I had developed a really ( in my opinion) good
> Raku body with one major issue.  While it was perfect for throwing when
> first mixed after a month or so it became so hard in the bag that
> additional water had to be added to make it throwable.  I posted the
> formula on Clayart and while I got many suggestions the correct answer came
> from Jon  at Laguna who said my problem was the 5% Wollastonite.  Once the
> Wollastonite was removed the clay stayed throwable in bags for a long long
> time and there was no negative repercussions caused by the removal.
> >>
> >> Don't know if any of the problem clays mentioned so far have
> Wollastonite but thought this might help someone.
> >>
> >> Paul
> >>
> >> Sent from my iPad
> >>
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