[Clayart] Fw: Blue haze on kiln shelves mystery

Dragonbelly Ceramics lisa at dragonbellyceramics.com
Thu Nov 10 03:41:53 UTC 2022

I've actually run a bunch of color tests with the High Calcium Semi Matt
glazes from Ron's Mastering Cone 6 Glazes, but we were having trouble (If I
remember correctly - it was quite some time ago) with keeping the glazes
from hard panning. We went with the base from our studio white glaze
because it's the most well behaved glaze we have on all our clay bodies.
(Yes - there are 4 that we stock. Not my decision. I would have gone with a
max of 2) It's never problematic in the bucket. Always easy to stir up into
suspension. Tolerates being applied thick or thin. All attributes important
to a community studio that also runs kids classes.

Recipe repeated here, for reference:

White Base:

minispar 200    46.1
Silica                 19.7
Gillespie Borate 13.5
Whiting               8.2
Dolomite             5.9
Zinc Oxide           3.9
Bentonite             2

Problematic color test:

+cobalt carb 2
+copper carb 2
+rutile            1.5

I don't have an insight-live account, but do use glazy. Glazy doesn't
calculate the limit formulas, but only the Stull charts. Do you recommend
using insight? Does it give substantially different information than glazy?

Best regards,
LJ Cohen

On Wed, Nov 9, 2022 at 6:49 PM David Woof <woofpots at hotmail.com> wrote:

> Hi Ron, Lisa,
> Yes I agree with what you said regarding the MgO.
> Because you had stated that you had run Lisa's glaze thru the Insight
> program, I was counting on you to assist Lisa in re-formulation of a glaze
> adjusted from the Gillespie to a Boron Frit such as 3134 or 3124 or
> possibly 3195 etc. depending on the other glaze material constituents
> because you had access to her original recipe, and I no longer do.
> One could also scrap the whole existing glaze and start over building a
> new glaze around a Boron Frit.
> (Exciting and learning prospect...!!!...???)
> Of course, it all depends on what you, Lisa, wish to do.
> And that you two can work it out provided both parties are willing.
> P.S. Ron,
> other than that I prefer a deflocculation method for glaze slop suspension
> in most glazing applications, and you favor Flocculation for most of
> same....I believe we see eye to eye on most other Ceramic issues.
> Especially that for many years we have beat the same drum regarding the
> science and ethics of creating stable glazes for vessels of Domestic
> Utility.
> Live long and be well my friend....... Love, David
> Misneach,
> David
> Woof...............................................................................................................................
> ***************************************************************************
> ________________________________
> From: ronroy at ca.inter.net <ronroy at ca.inter.net>
> Sent: Tuesday, November 8, 2022 10:46 AM
> To: Clayart international pottery discussion forum <
> clayart at lists.clayartworld.com>; David Woof <woofpots at hotmail.com>
> Subject: Re: [Clayart] Blue haze on kiln shelves mystery
> Hi David,
> I don't think that will work. The expansion goes up because the MgO
> goes down a lot and - the Gillespie borate helps float the glaze in
> the bucket.
> MgO is magnesium oxide and it has a low expansion rate so it's a good
> anti craze.
> The Gillespie borate, which is a good replacement for Gerstley borate
> is hydroscopic and helps keep glazes in suspension.
> The alumina stays the same in each case so adding clay to help the
> suspension issue would change the glaze.
> RR
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