[Clayart] glaze pops

[Robert Smith]

I don't know how you glaze your work, but when I throw a groggy body
(typically for raku firings), I first make sure I re-wet the surface after
the pot has been trimmed and use a metal rib nearly flush to the surface to
really smooth where I trimmed. But then, I brush on the glaze; I don't dip
or pour, as these techniques (and esp with thicker glazes) do leave
pinholing. If you dip or pour, you might want to brush a first coat
initially. The action of brushing "pushes" the glaze into the pores.

On Tue, May 8, 2018 at 7:53 AM, Pfeiffer Fire Arts <firearts at ardmore.net>
wrote:

> Glaze pops is what they look like but should be called blisters and pin
> holes. Looks like a bubble that pops and does not heal. We have been moving
> into a new batch of clay over the last year and it could in part be a clay
> problem but we do not see the same thing on our copper red firing. As the
> red is very fluid and our ox base is very stiff we then to think it a glaze
> problem.
> We don't use plaster so that should not be the problem.
>
> The clay does have a lot of grog in it and most of the problems do seem to
> be in the trimmed part of the ware but not always. I do take care to go
> over the trim parts with thawing slip to remove scratches and get a smooth
> surface.
>
> We have been thinking of changing clay but that is always a big deal and I
> am not sure what to replace the current one with.
> We are using a white ovenware ^10 clay (high-water phoenix ). Any other
> suggestion on a good ovenware clay?
>
> Dan & Laurel
>
> -----Original Message-----
> From: Clayart [mailto:clayart-bounces at lists.clayartworld.com] On Behalf
> Of Vince Pitelka
> Sent: Monday, May 07, 2018 8:56 PM
> To: 'Clayart international pottery discussion forum'
> Subject: Re: [Clayart] glaze pops
>
> Hi Dan -
> Can you be more clear about what you are referring to as glaze pops?  I am
> familiar with lime pops, which are usually the fault of the claybody
> (limestone contamination) or plaster contamination.  I am not familiar with
> "glaze pops."
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka at dtccom.net
> sites.tntech.edu/wpitelka/
>
> On Mon, May 7, 2018 at 1:03 PM, Pfeiffer Fire Arts <firearts at ardmore.net>
> wrote:
>
> > All,
> >
> >
> > After a number of years of not having a lot of problems with pop's in
> > the glaze it has got so bad as to put us out of business. I have been
> > making small changes in our glaze to reduce the surface tension hoping
> > this would help. It has not and the last firing was the worst of the
> > lot. I am not sure there are 5 pieces that we can sell.
> > This firing had a slow rise from 1700 to 1900 and then a hour dwell at
> > the top to cone 10 - 11. When slow about 2000 to give things time to
> > heel. If anything the pops are bigger with our new glaze then the old
> one.
> >
> > Our first glaze base glaze is:
> >
> > Epk                     12
> > Petalite                14
> > Wollastonite    20
> > Silca             20
> > Custer          33
> > Bentonite               1
> >
> > Our most recent attempt is to add a frit:
> >
> > Epk                     6
> > Cal Epk         6
> > Petalite                15
> > Wollastonite    17
> > Silca             20
> > Custer          29
> > Bentonite               .5
> > Ferro 3134              6
> > Veegum          .5
> >
> > While the calculated CEO is very close (8.60 and 8.61) to the same for
> > both versions we had some shivering when it was thick on one piece.
> > Anyone want to guess what to do next.
> >
> > Dan
> > PfeifferFirearts.com
> >
> >
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