[Clayart] Blue haze on kiln shelves (The Back Story)

Fri Nov 11 14:27:30 UTC 2022

I think I'm starting to understand better how to analyze glaze chemistry
now. I realized I do have access to looking at limit formulas in Glazy. In
the attached photo, on the stull charts there are 3 overlaid rectangles,
they represent 3 different cone 6 limits : Val Cushing's, Hasselbrith and
Roy's, and Green's.

I compared my original glaze with one of John's revisions and I can now
easily see that the revision takes the glaze from being out of 2 of the 3
limit formulas to right at the sweet spot where they all overlap.

My next question is this: Is there any way to tell, other than mixing a
test, how the color and glaze behavior will change as the chemistry changes?

(I'm thinking not! So it's off to the glaze lab with me...)

Best,
LJ

PS: this list is wonderful!

On Thu, Nov 10, 2022 at 11:13 PM Hank Murrow <hmurrow at efn.org> wrote:

> Dear Lisa and ClayArt friends;
>
> I hope that soon we will see the test results that will show that this
> team effort has solved
> the problem that Lisa noted from her test with the original recipe. Was
> the Gillespie to blame?
> Perhaps it was, and if not, perhaps another explanation will be revealed.
> This is how we learn
> what has occured in our kilns, by testing each conjecture we can imagine
> until evidence arrives
> to reveal the truth. I think for now we can be very proud that Clayart has
> responded generously
>  and thoughtfully to Lisa's question. I know I am.
>
> Bravo!  Hank in Eugene, OR
>
>
> > On Nov 10, 2022, at 7:00 PM, Dragonbelly Ceramics <
> lisa at dragonbellyceramics.com> wrote:
> >
> > Thank you so much for this, John. I'm just learning how to use glazy to
> > recalculate glazes. This is very helpful.
> >
> > Best,
> > LJ
> >
> > On Thu, Nov 10, 2022 at 10:15 AM John Post <johnpost89a at gmail.com>
> wrote:
> >
> >> Here are links to two recalculations of the White Base glaze that is
> having
> >> the spitting issues.
> >>
> >> The first revision is an exact match of the original glaze but swaps out
> >> the Gillespie for Frit 3134 and EPK.
> >> 1st revision link
> >> https://glazy.org/recipes/279862
> >>
> >> The second revision has 10% EPK which is a slight increase. I did this
> to
> >> help it behave well as a slurry.
> >> It also has some added silica to keep the alumina to silica ratio the
> same
> >> as the original.
> >> https://glazy.org/recipes/279863
> >>
> >> Original recipe link
> >> https://glazy.org/recipes/278970
> >>
> >> John Post
> >>
> >> On Thu, Nov 10, 2022 at 6:06 AM Dragonbelly Ceramics <
> >> lisa at dragonbellyceramics.com> wrote:
> >>
> >>> Thank you, David. As always, really excellent information. I am
> grateful.
> >>> Our bmix is the cone 5. All our clays are cone 5 or 6 stoneware. I do
> >>> suspect our kiln is not firing as well as it could be. It's been run
> hard
> >>> for quite some time now. We finally have a second kiln and can take
> this
> >>> one off line to be looked at and parts replaced as needed.
> >>>
> >>> While there are many joys in being part of a community studio, one of
> the
> >>> frustrations is the process of requisitioning supplies can be
> needlessly
> >>> complicated. We ran out of cone packs. When we finally received a new
> >>> supply, the 5's and 7s were fine. They gave us the wrong ones for the
> 6s.
> >>> So we're waiting. Currently firing with the 5 and 7 cones only.
> >>>
> >>> Best,
> >>> LJ Cohen
> >>>
> >>> On Wed, Nov 9, 2022 at 6:38 PM David Woof <woofpots at hotmail.com>
> wrote:
> >>>
> >>>> Hi Lisa,
> >>>> the intrinsic behavior of Gerstley and Gillespie Borates that produce
> >>>> problems similar to your description are usually from two mechanisms:
> >>>> Immiscibility and Solubility.
> >>>>
> >>>> "Immiscible" describes a formulation of materials that are physically
> >>>> resisting, or incapable of mixing well and attaining a homogenized
> >> state
> >>> in
> >>>> the glaze slop..
> >>>>
> >>>> Which means that the solubility of several of the materials present in
> >>> the
> >>>> glaze slop are prone to migrate, carrying away oxides as well, and so
> >>>> become separately volatile, with propensity to off-gas, spit, or fume,
> >>>> which create the halo's you describe.
> >>>>
> >>>> This agrees with what Hank, Bill, Ron...et.al....previously posted
> >>>> regarding the migration of soluble constituents.
> >>>> Gillespie Borate was formulated to provide a standardized Borate
> >> product
> >>>> when the mine was running out of commercially mineable Gerstley
> Borate.
> >>>> The soul crunching reality (I'm no fan) was to now provide a
> >>>> "Synthetically" consistent formulation,  though still providing the
> >>>> intrinsic character Old Gerstley was known for, and revered by some
> >>> folks.
> >>>>
> >>>> Of number one concern is that while the solubility of these borates
> >>>> contributes to the esteemed variegated Gillespi glaze surfaces via
> >>>> migration of the soluble oxides, this effect becomes exaggerated when
> >>> mixed
> >>>> with other slightly soluble glaze materials and oxides.
> >>>>
> >>>> There are other simple ways to achieve similar variegated glaze
> effects
> >>>> and these provide virtually trouble-free substitutions.
> >>>> Others may wish to chime in here as there are no secrets.
> >>>> ************************************************************
> >>>> Another question to ask: is the B-Mix your community studio is using
> >> cone
> >>>> 5 or the cone 10 version?  If cone 10, then at cones 5/6 the body is
> >> not
> >>>> becoming sufficiently dense or vitrified at any time during the 5/6
> >>> firing
> >>>> to prevent soluble constituents from migrating thru the body of the
> >> tile.
> >>>> +++++++++++++++++++++
> >>>> Also, your use of the pre-programed firing schedule could be suspect
> >>>> because the cone choice setting will eventually read false because of
> >> the
> >>>> natural degradation of the thermocouples, causing "drift" from
> >>> representing
> >>>> the actual cone achievement needed for Body/Glaze maturation.
> >>>> Set cone pacs in the firing setting to witness what your preprogrammed
> >>>> "cone 6  setting" is actually doing.
> >>>>
> >>>> Best wishes,
> >>>> David
> >>>>
> >>>
> >>
> Woof.........................................................................................................................
> >>>>
> >>
> *************************************************************************
> >>>> -------------- next part --------------
> >>>> An HTML attachment was scrubbed...
> >>>> URL: <
> >>>>
> >>>
> >>
> https://lists.clayartworld.com/pipermail/clayart/attachments/20221109/a6e53880/attachment.htm
> >>>>>
> >>>>
> >>>
> >>>
> >>> --
> >>>        http://www.dragonbellyceramics.com
> >>> *           where imagination meets function*
> >>> -------------- next part --------------
> >>> An HTML attachment was scrubbed...
> >>> URL: <
> >>>
> >>
> https://lists.clayartworld.com/pipermail/clayart/attachments/20221109/7acb6e90/attachment.htm
> >>>>
> >>>
> >> -------------- next part --------------
> >> An HTML attachment was scrubbed...
> >> URL: <
> >>
> https://lists.clayartworld.com/pipermail/clayart/attachments/20221110/3566eaf6/attachment.htm
> >>>
> >>
> >
> >
> > --
> >        http://www.dragonbellyceramics.com
> > *           where imagination meets function*
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
> > URL: <
> https://lists.clayartworld.com/pipermail/clayart/attachments/20221110/29ab5ed8/attachment.htm
> >
>
>

-- 
        http://www.dragonbellyceramics.com
*           where imagination meets function*
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.clayartworld.com/pipermail/clayart/attachments/20221111/b6846864/attachment.htm>