glazes theory and practice bryant hudson

Ceramic Glazes: Theory and Practice

Bryant Hudson

May 21, 2009

Goals

• Better understand how glazes work

• Become familiar with glaze compositions

• Become familiar with glaze ingredients

• Learn how to mix glazes

• Learn how to compare glazes

• Understand oxidation and reduction firing

• Look at the Firehouse Studio glazes in detail

What is a Glaze ?

• Glass that sticks to pottery

• Glazes are mostly Silica

• Pure Silica melts at 3100F

• Add Sodium and Calcium to lower melting point (fluxes)

• Add Aluminum to increase the viscosity

Periodic Table of the Elements

Lots of elements to consider

We want to work with common inexpensive materialsLow hazard and non-volatile

Elements we use in the current set of studio glazes

Of course everything is combined with Oxygen

Alkali Metals

Strong fluxes active at all temperatures

Lithium Carbonate (toxic)

Na Feldspar – F4 feldsparNepheline syeniteSodium Carbonate – Soda Ash (soluble, toxic)

Potassium Feldspar – Custer Feldspar

Alkaline Earth Metals and Zinc

Strong fluxes active at higher temperature

Calcium Carbonate – Whiting

Magnesium Calcium Carbonate – DolomiteMagnesium Silicate – TalcMagnesium Carbonate

Strontium CarbonateStrontium Oxide

Zinc Oxide

Non-metals and AluminumThese elements go into the basic glass network

Gerstley BorateBorax

Clays Feldspars

Silicon dioxide – Quartz, FlintClaysFeldspars

Calcium Phosphate – Bone Ash

Transition Metals - COLOR

Chromium Oxide (toxic)Iron Chromate (toxic)

Iron Oxide (Fe2O3 – red, Fe3O4 –black)

Copper Carbonate (toxic)

Cobalt Carbonate (toxic)

Titanium Dioxide – Rutile (>85% TiO2)

Zirconium Silicate – Zircopax, Ultrox

Tin Oxide

Opacifiers to decrease glaze transparency

3D BLACKTOMATO REDBOB'S BLUE MATTBRINGLE'S GREENBUTTERMILKDEPENDABLE REDGAIL'S WHITELAURA'S TURQUOISEMYSTERY BLUEPIER BLACKRACHEL'S BLUERUTILESEAFOAMSPECKLED LAVENDERTENMOKUWOO BROWN TO BLUEYELLOW SALT

Al2O3B2O3CaOCoOCr2O3CuOFeOK2OLi2OMgONa2OP2O5SiO2SnO2SrOTiO2ZnOZrO2

BentoniteBlack Iron OxideBone AshBoraxChrome OxideCobalt CarbonateCopper CarbonateCuster Feldspar Dolomite EPK Kaolin F-4 Feldspar Ferro 3134Gerstley BorateLithium CarbonateMagnesium CarbonateNepheline SyeniteOM-4 Ball ClayRed Iron OxideRutileSilica Strontium CarbonateTalcTenn #10 Ball ClayTin OxideUltrox (Zircopax)Whiting Zinc Oxide

17 Glazes from 18 Oxides derived from 27 different materials

BentoniteEPK (Kaolin)

OM-4 Ball ClayTennessee #10 Ball Clay

Custer FeldsparF-4 Feldspar

Nepheline SyeniteSpodumene

Clays

Feldspars

Primary source of Aluminum

Primary source of Li, Na, and K, and also provide Silica and

Aluminum

Soda AshLithium Carbonate

Strontium CarbonateStrontium Oxide

Magnesium CarbonateDolomite

TalcWhiting

Fluxes

Sources of Lithium, Sodium, Magnesium,

Calcium and Strontium

BoraxFerro 3134

Gerstley BorateSilica

Bone Ash

RutileTin OxideZinc Oxide

Ultrox (Zircopax)

Glass makers

Opacifiers

Sources of Boron, Silica and

Phosphorus

Sources of Titanium, Tin, Zinc and Zirconium

Chrome OxideCobalt CarbonateCopper Carbonate

Red Iron OxideBlack Iron Oxide

Colorants

Carbonates vs. Oxides or Silicates

• Carbonates

– Easier to make fine powders

– Lower density and easier to suspend in glaze

– Produce large amounts of CO2 – bubbles

– Generally more toxic

• Oxides or Silicates

– Can be coarse and heavy and hard to disperse

– No gas production

– Less toxic because they are harder to absorb

– Higher density means less material required

Cobalt Carbonate vs. Cobalt OxideCalcium Carbonate (whiting) vs. Wollastonite (CaSiO4)

Some of these compounds are toxic

Lithium , Copper, Cobalt and Chromiumare elements of concern

Eat a spoonful of these and you will get sick or die

We need small amounts in our diet to be healthy(1mg/d Li, 2mg/d Cu, 0.1 mg/d Co, 10mg/d Cr)

Chronic inhalation of dust

• Regular inhalation of fine silica dust causes long term health problems

• Fine silica powder is a mainstay of both clays and glazes

• This is the number one health concern in the studio

Keep Dust Levels Low !

• Clean up drips and spills

• Don’t dry sweep

• Don’t dry sand inside the studio

• If you have an apron, wash it regularly

• If you have a towel, keep it damp, wash it

• Transfer large bags of powder outside

• …

Material Properties

CAS # density solubility LD50 dust healthg/cm3 g/L H2O mg/kg (rat) hazard NFPA

Bentonite 1302-78-9 2.5 0 na serious 2Black Iron Oxide 1317-61-9 5.2 0 20000 nuisance 0Bone Ash 1306-06-5 3.1 0 10000 nuisance 0Borax 1330-43-4 2.4 25 2400 moderate 1Chrome Oxide 1308-38-9 5.2 0 10000 serious 2Cobalt Carbonate 12602-23-2 4.1 0 640 serious 2Copper Carbonate 12069-69-1 4.0 0 1350 nuisance 1Custer Feldspar 68476-25-5 2.6 0 na serious 1Dolomite 16389-88-1 2.8 0 6450 nuisance 1EPK Kaolin 1332-58-7 2.7 0 na serious 2F-4 Feldspar 68476-25-5 2.6 0 na serious 1Ferro Frit 3134 65997-18-4 2.0 0 na moderate 1Gerstley Borate 12046-09-2 2.4 5 >5000 nuisance 0Lithium Carbonate 554-13-2 2.1 13 525 serious 2Magnesium Carbonate 546-93-0 3.0 0 na nuisance 1

CAS # - universal database numberLD50 (rat) – 50% of rats will die if the consume this much materialNFPA Health – 0 nontoxic, 1 slightly toxic, 2 moderately toxic, 3 highly toxic, 4 extremely toxic

CAS # density solubility LD50 dust healthg/cm3 g/L H2O mg/kg (rat) hazard NFPA

Nepheline Syenite 37244-96-5 2.6 0 na nuisance 0OM-4 Ball Clay 1332-58-7 2.5 0 na serious 2Red Iron Oxide 1309-37-1 5.2 0 20000 nuisance 1Rutile 1317-80-2 4.1 0 na nuisance 0Silica 14808-60-7 2.7 0 na serious 2Soda Ash (sodium carbonate) 497-19-8 2.5 300 4090 moderate 2Strontium Carbonate 1633-05-2 3.5 0 >2000 nuisance 1Talc 14807-96-6 2.6 0 na moderate 1Tenn #10 Ball Clay 1332-58-7 2.5 0 na serious 2Tin Oxide 1332-29-2 7.0 0 20000 serious 2Ultrox (Zircopax) 14940-68-2 4.7 0 na serious 1Whiting (calcium carbonate) 471-34-1 2.8 0 6450 nuisance 1Wollastine 13983-17-0 2.8 0 na nuisance 0Zinc Oxide 1314-13-2 5.6 0 na nuisance 0

Useful Information

• http://digitalfire.com/4sight/material/

http://digitalfire.com/4sight/material/

Melting Mixtures

• Many of the glaze compounds melt at very high temperatures

• Mixtures of these compounds melt at lower temperatures (Eutectic = easy to melt)

A simple real-world phase diagram

The first objects in the solar system were ceramic

The small white inclusions are Ca-Al-silicates

We can study their compositions and compare to known phase diagrams to infer the conditions under which they formed

On an atomic scale our ingredients are big

• Melting begins at the contact points

• Our “small” particles are still tens of thousands of atoms wide

• This affects how the glaze melts

Kilns

Electric• Oxygen atmosphere

• Precise temperature control

• Generally below 2250F (cone 6) to increase filament life but can go to cone 10

• Reduction difficult

Gas or Wood

• Combustion gas atmosphere

• Moderate temperature control

• Routine operation to 2350F (cone 10)

• Capable of producing reduction atmosphere

• Difficult to control

Combustion

• CH4 + 2O2 CO2 + 2H2O (890 J/mole)

– All the oxygen is consumed

– Maximum heat production

• CH4 + O2 CO + H2 + H2O (36 J/mole)

– Not enough oxygen for complete combustion

– Most of the fuel energy escapes

– Large amount of carbon monoxide produced

There are many possibilities

• CH4 +yO2 aCO2 + bCO +cH2 + dH2O + eC

• Even molecules like CH3OH (methanol)

• Details matter - burner geometry, kiln size

• Gas kilns differ greatly

Why care about reduction ?

• CO + 2CuO Cu2O + CO2

• Color changes in the transition metal colorants

Timing in the firing matters

• Before the glaze melts, the glaze and clay are porous and interact with the kiln atmosphere

• Once the glaze melts, the interaction with the kiln atmosphere takes place by diffusion –much slower

Timing in cooling matters

• Once the burners are off, the atmosphere suddenly changes to being oxygen rich

• As the glaze cools, some liquids or solids by come out of solution

• Crystal formation is critical to copper red glazes

• Crystal formation and phase separation give rise to many of the effects we like

Safety in firing the gas kiln

• Carbon Monoxide – very toxic

• You can hurt your eyes looking in the kiln

• Volatile compounds

– organic, sulfurous, metallic compounds

Gases coming from the kiln, especially during reduction are dangerous. Stay away from the kiln during firing. Beware of the possibility of kiln exhaust entering the studio

Evaluating Glaze Compositions

• Lots of different ingredients bring in some of the same oxides and it can be hard to compare glaze recipes

• We need to be able to transform glaze recipes into lists of basic oxides

• Instead of using weights, it is useful to calculate relative number of molecules

Calculating Molecular Fractions• Need to know the composition of each ingredient and what

disappears during firing

Custer Feldspar

CaO 0.30 K2O 10.28 Na2O 2.91 Al2O3 17.35 SiO2 69.00 Fe2O3 0.12

LOI 0.04

LOI = Loss On Ignition

OM #4 Ball Clay

CaO 0.30 K2O 1.00 MgO 0.40 Na2O 0.30 TiO2 1.20 Al2O3 27.90 SiO2 55.20 Fe2O3 1.10

LOI 12.60

Calcium Carbonate(whiting)

CaO 56.10

LOI 43.90

Values are weight %

Add pieces and normalize

70% 10% 20%

Oxide Mole wt. Custer F. OM4 BC Whiting weight moles mole %

CaO 56.1 0.3 0.3 56.1 11.5 0.2043 14.8%

K2O 94.2 10.3 1.0 7.3 0.0775 5.6%

MgO 40.3 2.9 0.4 2.1 0.0515 3.7%

Na2O 62.0 0.3 0.0 0.0005 0.0%

TiO2 80.1 1.2 0.1 0.0015 0.1%

Al2O3 101.9 17.4 27.9 14.9 0.1466 10.6%

SiO2 60.0 69.0 55.2 53.8 0.8970 65.0%

Fe2O3 159.7 0.1 1.1 0.2 0.0012 0.1%

A recipe for a simple clear glaze

Seger Unity Formula

Oxide Mole % Seger Oxide Mole % Seger

CaO 0.1480 0.61 SiO2 0.6500 2.678

K2O 0.0561 0.23 Al2O3 0.1062 0.438

MgO 0.0373 0.15 TiO2 0.0011 0.004

Na2O 0.0004 0.00

Fe2O3 0.0009 0.00

sum 0.2427

The Seger formula for a cone 6 cone has SiO2 = 6, a cone 7 cone has SiO2 = 7…

Seger Formula: Normalize the mole % values to the sum of the fluxes

Mixing Glazes

• Read and understand the recipe

• Check to see if you have the ingredients

• Equipment:– A scale to weigh materials

– Containers to weigh materials and mix materials

– Sieves to do the final mixing

– Graduated cylinder and funnel to measure specific gravity

– Protective equipment, dusk mask, gloves …

What I do to mix a glaze

1) Start with 0.5 liter of water per 1000g of dry material

2) Start with the hard to mix materials first

1) Bentonite, ball clay, EPK

3) Mix each ingredient as you add it

4) Add water to bring the specific gravity close to the correct value so the glaze isn’t too thick but still needs a little more water

5) Take notes (and keep them) of what you did

6) Take a break (30 min – a day) for material to hydrate – it will be easier to sieve and mix

What I do to mix a glaze7) Spend several minutes with the drill mixer to thoroughly

mix the glaze

8) Sieve the glaze a couple time (80 mesh, check recipe)

9) Check the specific gravity and add water to bring it to the correct value (about 1.6 – check recipe)

10) Check the thickness (viscosity). Test how it coats a piece of bisque pottery (want about 1mm)

11) If the glaze is thin, add epsom salt (MgSO4) (20g/10000g glaze) at a time until the glaze is thickened – no more than 100g/10000g total

12) Clean up the mess

Measuring Specific Gravity

• Specific gravity is the measured density divided by the density of water

• Weigh 100 ml of glaze and divide the weight by 100

• Measuring specific gravity is the best way to know how much water to add

Glaze Flocculation• Glazes are complex liquids – a suspension of fine particles

• Clay particles have interesting surface properties and depending on what’s dissolved in the glaze, they will stick together

• Dissolved Ca and Mg will cause glazes containing clay to flocculated

• A flocculated glaze works well for dipping application

• If a glaze doesn’t contain much clay, bentonite can be added (1-2%)

• Some glazes will de-flocculate over time due to materials going into solution. Add small amounts of epsom salt (MgSO4) to re-flocculate the glaze

Glaze Flocculation• http://www.claytimes.com/articles/glazeadjusting.html

• Adjusting Glazes for Application by Pete Pinnell, From the March/April and May/June 1998 issues of Clay Times

http://www.claytimes.com/articles/glazeadjusting.html

Measuring Glaze Thickness

• Applying glaze at the proper thickness is important

• Know the glaze and measure the thickness

Use a razor blade to scrape a 90 degree scratch in the glaze. The width at the

top is twice the thickness of the glaze

Summary of Glazes

SiO2 Al2O3 B2O3 P2O3 TiO2 SnO2 ZrO2 Li2O K2O Na2O CaO MgO SrO ZnO Cr2O3 CoO CuO FeO

3D BLACK 0.75 0.07 0.01 0.03 0.08 0.004 0.05

TOMATO RED 0.65 0.08 0.02 0.02 0.03 0.08 0.05 0.06

BOB'S BLUE MATT 0.60 0.12 0.02 0.07 0.01 0.17 0.013

BRINGLE'S GREEN 0.51 0.09 0.01 0.04 0.02 0.06 0.13 0.10 0.033 0.01

BUTTERMILK 0.65 0.05 0.03 0.03 0.02 0.01 0.11 0.09

DEPENDABLE RED 0.65 0.07 0.02 0.005 0.02 0.04 0.12 0.02 0.04 0.004

GAIL'S WHITE 0.67 0.12 0.02 0.04 0.02 0.04 0.08

LAURA'S TURQUOISE 0.51 0.11 0.03 0.02 0.01 0.30 0.002 0.020

MYSTERY BLUE 0.71 0.07 0.03 0.03 0.01 0.14 0.006

PIER BLACK 0.50 0.12 0.01 0.04 0.02 0.14 0.08 0.02 0.042 0.03

RACHEL'S BLUE 0.69 0.07 0.04 0.03 0.03 0.13 0.007

RUTILE 0.63 0.08 0.07 0.02 0.01 0.14 0.05

SEAFOAM 0.70 0.07 0.03 0.03 0.01 0.14 0.022

SPECKLED LAVENDER 0.67 0.06 0.02 0.005 0.02 0.04 0.03 0.12 0.01 0.03 0.003 0.003

TENMOKU 0.68 0.07 0.03 0.01 0.12 0.08

WOO BROWN TO BLUE 0.70 0.07 0.03 0.03 0.01 0.12 0.03

YELLOW SALT 0.54 0.11 0.06 0.02 0.07 0.09 0.07 0.04

Values are mole %

3D BLACK FH

Silica 37.0

F-4 Feldspar 44.0

Whiting 12.0

EPK Kaolin 7.0

Red Iron Oxide 6.4

Cobalt Carbonate 0.8

3D BlackSeger Mol%

KNO 0.239 4.42%

CaO 0.457 8.44%

Al2O3 0.372 6.87%

SiO2 4.043 74.65%

TiO2 0.001 0.02%

K2O 0.062 1.14%

Na2O 0.178 3.28%

CoO 0.034 0.43%

FeO 0.280 5.18%

TOMATO RED FH

F-4 Feldspar 48.22

Silica 25.89

EPK Kaolin 7.14

Magnesium Carbonate 7.14

Bone Ash 11.61

Black Iron Oxide 7.14

Tomato RedSeger Mol%

KNO 0.206 5.19%

CaO 0.325 8.21%

MgO 0.215 5.43%

Al2O3 0.311 7.85%

P2O5 0.092 2.31%

SiO2 2.56 64.59%

TiO2 0.001 0.02%

K2O 0.074 1.87%

Na2O 0.132 3.33%

FeO 0.254 6.40%

BOB'S BLUE MATT FH

Nepheline Syenite 53

Tenn #10 Ball Clay 7

Silica 8

Strontium Carbonate 32

Bentonite 2

Copper Carbonate 2

Bob’s Blue MattSeger Mol%

KNO 0.316 9.01%

CaO 0.021 0.59%

MgO 0.009 0.25%

SrO 0.607 17.28%

Al2O3 0.410 11.68%

SiO2 2.097 59.74%

TiO2 0.004 0.10%

K2O 0.078 2.22%

Na2O 0.239 6.79%

CuO 0.045 1.29%

FeO 0.002 0.07%

Custer Feldspar 45.0

Whiting 7.0

OM-4 Ball Clay 13.0

Strontium Carbonate 25.0

Zinc Oxide 10.0

Copper Carbonate 5.0

Rutile 1.0

Red Iron Oxide 1.25

Seger Mol%

KNO 0.145 5.7%

CaO 0.147 5.8%

MgO 0.003 0.1%

ZnO 0.248 9.8%

SrO 0.341 13.5%

Al2O3 0.222 8.8%

SiO2 1.286 50.7%

TiO2 0.029 1.2%

K2O 0.100 4.0%

Na2O 0.045 1.8%

CuO 0.082 1.4%

Bringle’s Green

Gerstley Borate 9.63

Dolomite 6.23

Whiting 8.25


EPK Kaolin 6.23

Talc 12.38

Silica 22.11

Zircopax 8.25

Seger Mol%

KNO 0.15 3.5%

CaO 0.47 11.3%

MgO 0.39 9.3%

Al2O3 0.20 4.9%

B2O3 0.12 2.9%

SiO2 2.69 64.9%

ZrO2 0.13 3.2%

TiO2 0.00 0.0%

K2O 0.09 2.1%

Na2O 0.06 1.4%

Buttermilk

Zinc Oxide 4.5

Talc 3.5

Whiting 13.0

Ferro 3134 10.8

F4 Feldspar 45.5

EPK Kaolin 5.2

Silica 16.0

Bentonite 1.5

Tin Oxide 1.0


Seger Mol%

KNO 0.249 6.1%

CaO 0.503 12.4%

MgO 0.077 1.9%

ZnO 0.153 3.8%

Al2O3 0.302 7.5%

B2O3 0.100 2.5%

SiO2 2.637 65.0%

TiO2 0.001 0.0%

K2O 0.067 1.7%

Na2O 0.182 4.5%

CuO 0.015 0.4%

Dependable Red

Gail’s White


EPK Kaolin 19.0

Dolomite 9.5

Talc 9.5

Zircopax 4.8

KNO 0.335 6.4%

CaO 0.224 4.3%

MgO 0.436 8.3%

Al2O3 0.627 12.0%

SiO2 3.496 66.9%

ZrO2 0.098 1.9%

TiO2 0.003 0.1%

K2O 0.230 4.4%

Na2O 0.105 2.0%

Laura’s Turquoise

Whiting 38.1


EPK Kaolin 28.6

Silica 9.5



Rutile 2.9

Seger Mol%

KNO 0.083 2.9%

CaO 0.852 29.7%

Al2O3 0.327 11.4%

SiO2 1.454 50.8%

TiO2 0.084 2.9%

K2O 0.057 2.0%

Na2O 0.026 0.9%

CoO 0.005 0.2%

CuO 0.056 2.0%

Mystery Blue

EPK Kaolin 10

Whiting 20

Silica 30

Custer Feldspar 40

Rutile 4

Copper Carbonate 1

Seger Mol%

KNO 0.228 4.3%

CaO 0.738 13.8%

Al2O3 0.382 7.2%

SiO2 3.780 70.7%

TiO2 0.185 3.5%

K2O 0.157 2.9%

Na2O 0.071 1.3%

CuO 0.030 0.6%

Pier BlackCuster Feldspar 42.7

EPK Kaolin 23.6

Dolomite 23.6

Whiting 4.7

Borax 5.4


Black Iron Oxide 3.2

Chrome Oxide 3.4

KNO 0.157 5.5%

CaO 0.402 14.1%

MgO 0.226 7.9%

Al2O3 0.339 11.9%

B2O3 0.030 1.1%

SiO2 1.430 50.2%

TiO2 0.002 0.1%

K2O 0.105 3.7%

Na2O 0.052 1.8%

CoO 0.119 4.2%

FeO 0.094 3.4%

Cr2O3 0.048 1.7%

Rachel’s Blue

Custer Feldspar 35

OM-4 Ball Clay 17

Whiting 12

Silica 19

Ferro 3134 17


Seger Mol%

KNO 0.302 5.9%

CaO 0.650 12.7%

MgO 0.006 0.1%

Al2O3 0.369 7.2%

B2O3 0.200 3.9%

SiO2 3.557 69.3%

TiO2 0.009 0.2%

K2O 0.140 2.7%

Na2O 0.162 3.2%

CoO 0.037 0.7%

RutileDolomite 15.8


Whiting 10.1

EPK Kaolin 17.8

Silica 26.3

Rutile 8.0

Seger Mol%

KNO 0.148 3.2%

CaO 0.622 13.5%

MgO 0.226 4.9%

Al2O3 0.370 8.0%

SiO2 2.906 63.2%

TiO2 0.321 7.0%

K2O 0.102 2.2%

Na2O 0.046 1.0%

Seafoam

Custer Feldspar 40

Silica 30

Whiting 20

EPK Kaolin 10

Rutile 4

Copper Carbonate 4

Seger Mol%

KNO 0.210 4.2%

CaO 0.678 13.6%

Al2O3 0.351 7.0%

SiO2 3.471 69.5%

TiO2 0.170 3.4%

K2O 0.144 2.9%

Na2O 0.066 1.3%

CuO 0.109 2.2%

Speckled LavenderZinc Oxide 4.0

Lithium Carbonate 2.0

Whiting 14.0

Ferro 3134 7.0

Silica 20.0


Strontium Carbonate 3.0

Bentonite 1.0

Tin Oxide 1.0


Seger Mol%

KNO 0.251 6.3%

CaO 0.464 11.6%

MgO 0.002 0.1%

ZnO 0.136 3.4%

Li2O 0.075 1.9%

SrO 0.056 1.4%

Al2O3 0.239 6.0%

B2O3 0.064 1.6%

SiO2 2.685 67.0%

K2O 0.150 3.8%

Na2O 0.101 2.5%

CuO 0.013 0.3%

SnO2 0.018 0.46%

Tenmoku


EPK Kaolin 10.3

Whiting 18.3

Silica 28.0

Red Iron Oxide 9.8

Seger Mol%

KNO 0.180 4.4%

CaO 0.491 12.1%

Al2O3 0.296 7.3%

SiO2 2.764 68.1%

TiO2 0.001 0.0%

K2O 0.124 3.0%

Na2O 0.056 1.4%

FeO 0.329 8.1%

Woo Brown to BlueWhiting 18.0


OM-4 Ball Clay 13.0

Silica 27.0

Red Iron Oxide 4.0

Rutile 4.0

Seger Mol%

KNO 0.223 4.5%

CaO 0.603 12.1%

MgO 0.004 0.1%

Al2O3 0.348 7.0%

SiO2 3.465 69.5%

TiO2 0.172 3.5%

K2O 0.154 3.1%

Na2O 0.069 1.4%

FeO 0.170 3.4%

Yellow Salt

Nepheline Syenite 200 61.0

Dolomite 20.0

OM-4 Ball Clay 4.0

Zircopax 15.0

Bentonite 1.0

Red Iron Oxide 4.0

Seger Mol%

KNO 0.322 9.3%

CaO 0.318 9.2%

MgO 0.233 6.7%

Al2O3 0.383 11.1%

SiO2 1.875 54.1%

ZrO2 0.206 5.9%

TiO2 0.002 0.0%

K2O 0.078 2.3%

Na2O 0.244 7.0%

FeO 0.127 3.7%

SiO2 Al2O3 B2O3 ZrO2 K2O Na2O CaO MgO FeO

GAIL'S WHITE 0.67 0.12 0.02 0.04 0.02 0.04 0.08

BUTTERMILK 0.65 0.05 0.03 0.03 0.02 0.01 0.11 0.09

YELLOW SALT 0.54 0.11 0.06 0.02 0.07 0.09 0.07 0.04

SiO2 Al2O3 B2O3 P2O3 TiO2 K2O Na2O CaO MgO Cr2O3 CoO FeO

3D BLACK 0.75 0.07 0.01 0.03 0.08 0.004 0.05

WOO BROWN TO BLUE 0.70 0.07 0.03 0.03 0.01 0.12 0.03

TENMOKU 0.68 0.07 0.03 0.01 0.12 0.08

TOMATO RED 0.65 0.08 0.02 0.02 0.03 0.08 0.05 0.06

PIER BLACK 0.50 0.12 0.01 0.04 0.02 0.14 0.08 0.02 0.042 0.03

SiO2 Al2O3 TiO2 K2O Na2O CaO MgO SrO ZnO CoO CuO FeO

MYSTERY BLUE 0.71 0.07 0.03 0.03 0.01 0.14 0.006 0.006

SEAFOAM 0.70 0.07 0.03 0.03 0.01 0.14 0.022

WOO BROWN TO BLUE 0.70 0.07 0.03 0.03 0.01 0.12 0.03

RUTILE 0.63 0.08 0.07 0.02 0.01 0.14 0.05

LAURA'S TURQUOISE 0.51 0.11 0.03 0.02 0.01 0.30 0.002 0.020

BRINGLE'S GREEN 0.51 0.09 0.01 0.04 0.02 0.06 0.13 0.10 0.033 0.01

SiO2 Al2O3 B2O3 SnO2 Li2O K2O Na2O CaO MgO SrO ZnO CoO CuO

DEPENDABLE RED 0.65 0.07 0.02 0.005 0.02 0.04 0.12 0.02 0.04 0.004

SPECKLED LAVENDER 0.67 0.06 0.02 0.005 0.02 0.04 0.03 0.12 0.01 0.03 0.003 0.003

A tiny bit of cobalt makes a big difference

glazes theory and practice bryant hudson

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