Suds Acres Bed & Breakfast on wed 11 oct 00
I'm coming back to ceramics after a couple years break and I'm still
trying to figure out basic glaze problems. I made ^10 redux ware at
college (probably nothing food safe) & not much exp. firing etc. I'm
kinda on my own here now, so I'd really appreciate some help. I have a
lot of questions (and doubts) from not working with glazes for a few year=
s.
I've got a Coneart kiln now that I've have figured out how to use. I've
been using a bag of some premixed clear glaze from Laguna that crazes on
my clay which is Laguna's Aspen(^5-6). First Question: What can I do to
fix this? Add something?
I mixed glazes in college and so I am familiar with it, plus in the time
I wasn't producing any wares I have still been occasionally studying and
building a really great library of ceramics books. Please bear with me
if the answers to my questions are obvious to you. I do have Hamer's and
others I am reading voraciously, but only so much is making sense. I am
sure after I get going it will gel, but for now it's all floating around
loosely arranged in my head. Confusing.
Now to get down to business, I am going to get set-up to mix my own
glazes.=20
I want to start with a Limestone base glaze - clear and white liner
glazes that will also be food safe with standard metallic oxides as
colorants. I understand the need for testing the glazes for leaching and
have info on that. What colorants work especially well with this? This
is an alkaline glaze right, so it'll tend to craze?
What constitutes flux-saturation in a glaze? I have been contemplating
using several glazes from the CeramicsWeb GlazeBase for ^5-6 that were
posted by Val Cushing. Many have over 50% Custer Feldspar or Nephaline
Syenite plus Whiting and stuff... Is that too much for food safe ware?=20
I know matt glazes aren't good for dinnerware, but what about satin?
Semi-gloss? How matt is too matt? As an aside..What is a buttery glaze -
one that looks like cool whip or what? This has been bugging me. No one
has ever shown me a glaze and said THIS is a buttery glaze.
Also, here is the preliminary list of materials I want to order for
basic glaze testing and formulation of a few basic glazes, then moving
on to test and formulate decorative glazes like crystalline glazes. Is
there something I should have I do not list? Are my proportions way out
of whack?
100 pounds each: Custer Feldspar, Nepheline Syenite, Flint, and Whiting
50 pounds each: EPK, Kona F-4 Spar=20
25 pounds each: Dolomite, Talc, Zinc Oxide, Spodumene
5 pounds each: Strontium, Bone Ash (watching out for mad cows, of
course), Cornwall stone, Ferro Frit 3110, Bentonite
1 pound each: cobalt oxide, copper carbonate, chromium oxide, red iron
oxide, nickel oxide, rutile, tin oxide, titanium dioxide, zircopax=20
I have one ^4 crystalline glaze from Out of the Earth and Into the Fire.
In the Studio Potter article online about the midfire range, also
curiously enough by Val Cushing, he says that you can produce
crystalline and aventurine glazes in this range. I haven't seen many
recipes in this range however. Does anyone have any they would be
willing to send me? Also, I have never seen an aventurine glaze
personally. A few artists here use crystalline glazes (about 3 glazes in
limited production locally so far), and I was starting to do them in the
redux ^10 kiln at school. No aventurine glazes are being produced here
to my knowledge. Does anyone have a recipe they are willing to share, or
info on them? What can I do to try and create one? Does anyone have a
picture of an aventurine glaze online?
Following are three of the glazes I am looking at for food-safe dinnerwar=
e:
Am I on the right track?? How do you use limit charts or whatever you
call that and where do I find info on that? Silica to Alumina Ratios -
huh? And (DUH), I forgot.. which goes in the bucket first, the water or
the glaze materials? I'm not kidding, and I hope I don't irritate
anyone, you'd be surprised how long it takes to find this stuff out
searching through textbooks. =20
I am also going to do Vince's terra sig recipe and get the stuff needed
to do that. I already have Kentucky ball clay and RedArt clay. Am I
trying to do too much at once? I want get a raku kiln and start that
again in the spring... Am I crazy or just normal??? :) Love all you
guys and hope someone remembers me from the couple of years I was
jabbering on Clayart and so glad to be back in clay after being so sick
for so long (they thought I had MS, but now say Fibromyalgia...anyways,
hope I never get that bad again!!), =20
Samantha Tomich, Paauilo, Hawaii
Glaze Name: Transparent 1
cone: 5 - 6
color:Transparent
surface:shiny glossy
firing:Ox or Red
date: 6/4/96
recipe:=20
Nepheline Syenite 56.00
Whiting 9.00
Talc 6.00
Flint 23.00
EPK 6.00
Totals: 100.00 %
comments:
From the NCECA GlazeBase Glaze Recipe Database at SDSU.
If you find this glaze useful, please consider submitting
one of your own tested glazes to add to the database.=20
estimated thermal expansion: 76.32x10-7/=B0C
Unity Formula for Transparent 1:
0.102 K2O 0.568 Al2O3 3.989 SiO2=20
0.337 Na2O 7.0:1 Si:Al Ratio
0.394 CaO=20
0.167 MgO=20
Percentage Analysis:
67.15 % SiO2
16.23 % Al2O3
2.69 % K2O
5.85 % Na2O
6.19 % CaO
1.89 % MgO
Talc: wear a NIOSH approved dust mask when handling dry material
Flint: free silica-wear a NIOSH
approved dust mask when handling dry material=20
Glaze Type: Ca Na . Firing type: Ox or Red. From Val Cushing. VC ed=20
=20
Glaze Name: Glossy (Would this be too matt??)
cone: 5 - 6
color:Opaque White
surface:Satin
firing:Ox or Red
date: 6/4/96
recipe:=20
Kona F-4 Spar 19.00
Custer Feldspar 19.00
Nepheline Syenite 19.00
Dolomite 25.00
Whiting 6.00
Kaolin 12.00
Totals: 100.00 %
Also add:
Tin Oxide 7.50
comments:
From the NCECA GlazeBase Glaze Recipe Database at SDSU.
If you find this glaze useful, please consider submitting
one of your own tested glazes to add to the database.=20
estimated thermal expansion: x10-7/=B0C
Unity Formula for Glossy:
0.091 K2O 0.352 Al2O3 1.630 SiO2=20
0.134 Na2O 0.002 TiO2=20
0.466 CaO 4.6:1 Si:Al Ratio
0.309 MgO=20
Percentage Analysis:
51.69 % SiO2
18.94 % Al2O3
4.52 % K2O
4.39 % Na2O
13.80 % CaO
6.58 % MgO
0.08 % TiO2
A glossier version of Polished Matt. Glaze Type: Ca Mg AlMatt.
Firing type: Ox or Red. From Val
Cushing. VC ed=20
Glaze Name: Matt Base 5 (Would THIS be too matt??)
cone: 5 - 6
color:SemiOpaque White
surface:Satin Matte
firing:Ox or Red
date: 6/4/96
recipe:=20
Custer Feldspar 40.00
Ferro frit 3124 9.00
Talc 9.00
Whiting 16.00
EPK 10.00
Flint 16.00
Totals: 100.00 %
comments:
From the NCECA GlazeBase Glaze Recipe Database at SDSU.
If you find this glaze useful, please consider submitting
one of your own tested glazes to add to the database.=20
estimated thermal expansion: x10-7/=B0C
Unity Formula for Matt Base 5:
0.136 K2O 0.352 Al2O3 2.982 SiO2=20
0.088 Na2O 0.055 B2O3 8.5:1 Si:Al Ratio
0.558 CaO=20
0.218 MgO=20
Percentage Analysis:
64.62 % SiO2
12.95 % Al2O3
1.38 % B2O3
4.62 % K2O
1.97 % Na2O
11.29 % CaO
3.17 % MgO
Glaze Type: Ca Mg. Firing type: Ox or Red. From Val Cushing. VC ed
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