[Clayart] Question about resizing/estimating clay for custom
Kim Overall
overallk at yahoo.com
Thu Nov 10 14:22:49 UTC 2022
about increasing/decreasing clay weight to resize...
would it work to calculate the difference in size as a percentage and use that percentage to increase/decrease clay weight?
ie: if you use 6 oz wet clay for a finished 8 ounce 3-1/2"w x <4"h mug and
you want to increase it to a monster 64 ounce mug,would that be 8x6 = 48 oz clay
Kim Overall
808.825.0158 (c)
On Thursday, November 10, 2022 at 07:06:37 AM CST, clayart-request at lists.clayartworld.com <clayart-request at lists.clayartworld.com> wrote:
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Today's Topics:
1. Re: Fw: Blue haze on kiln shelves mystery (Dragonbelly Ceramics)
2. Re: Blue haze on kiln shelves (The Back Story)
(Dragonbelly Ceramics)
3. Re: Question about resizing/estimating clay for custom
(David Woof)
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Message: 1
Date: Wed, 9 Nov 2022 22:41:53 -0500
From: Dragonbelly Ceramics <lisa at dragonbellyceramics.com>
To: Clayart international pottery discussion forum
<clayart at lists.clayartworld.com>
Subject: Re: [Clayart] Fw: Blue haze on kiln shelves mystery
Message-ID:
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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:
WB-10:
+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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--
http://www.dragonbellyceramics.com
* where imagination meets function*
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Message: 2
Date: Wed, 9 Nov 2022 22:48:30 -0500
From: Dragonbelly Ceramics <lisa at dragonbellyceramics.com>
To: Clayart international pottery discussion forum
<clayart at lists.clayartworld.com>
Subject: Re: [Clayart] Blue haze on kiln shelves (The Back Story)
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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.........................................................................................................................
> *************************************************************************
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--
http://www.dragonbellyceramics.com
* where imagination meets function*
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Message: 3
Date: Thu, 10 Nov 2022 05:44:28 +0000
From: David Woof <woofpots at hotmail.com>
To: Clayart international pottery discussion forum
<clayart at lists.clayartworld.com>
Subject: Re: [Clayart] Question about resizing/estimating clay for
custom
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Hi Kathi,
I consider it "cost of doing business" to step outside of my usual production, if it's just a larger piece of similar ware. I just figure it out and do it.
As to your Lassana dish: It is hard to suggest weight because of your individual throwing style and the form i.e. with trimmed foot or not, rim embellishments or thickness, outward turn etc.
Try a larger poundage and see what you get from it.
If still too small try again till you succeed.
With these extra trials you will simply have saleable ware someone else will buy.
Good pots always sell.
I always make one or two extras of the larger size anyway, as insurance, because things can go wrong when we need them not to.
When you arrive at the correct poundage, remember to make the form larger by the percentage of the fired shrinkage of your body. As I'm sure you know, metric makes for simple accurate measuring calculations.
Now the "FUN" part:
If it's an unusual idea (someone else's idea) and it intrigues me and challenges me I ask for a nonrefundable deposit of 50% on the work, (estimated R&D included)
Or...... if Idea is too off the wall, I tell them that I'm not taking any more commissions until I "get caught up."
And their great idea dies in its embryonic state before I ever "get caught up."
Then too, sometimes one can tell them the idea is intriguing.....But if you were to do it you would have to "make these modifications" and if they see the value of your professional input, perhaps you can still do the commission. After all, you are the "artist." So sell yourself as such.
Sometimes it's a good save!!!
Always take the 50% non-refundable deposit.
Misneach,
David Woof..............................................................................................................
***************************************************************************
________________________________
From: Clayart <clayart-bounces at lists.clayartworld.com> on behalf of Kathi Koester <mrskathikoester at gmail.com>
Sent: Wednesday, November 9, 2022 7:38 AM
To: Clayart international pottery discussion forum <clayart at lists.clayartworld.com>
Subject: [Clayart] Question about resizing/estimating clay for custom
Dear Clayart,
Occasionally, I have a repeat customer that wants something custom. Is
there a mathematical/way to estimate how many more pounds when you upsize?
If my normal lasagna pan is 6 pounds of clay, but the customer wants a
15?x4? Casserole - because they constantly entertain their 10 family
members who live in town - how many pounds should I try? 10?
(I know how much clay it takes for my various sizes of bowls, or utensil
holder vs wine chiller, or a cake pedestal. But I?m not in the habit of
making massively different sized casseroles.)
Also, the few 13?+ I have made over the years, I put a canvas custom cut on
my 15? wheel head (my wonderful Klopphenstein kickwheel) and then I dry it
on sheet rock.
Any helpful tips are welcome.
Kindest regards,
Kathi
MN
--
Sincerely,
Kathi Koester
612-867-0829
MAKNART Ceramics
https://maknartceramics.square.site/
Author: Our Piano Teacher ISBN: 978-1-64416-853-0
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