Mastering Cone 6 Glazes
Foreword ……………………………………………………………….. 7
7
Preface
9
Acknowledgments
10
A Note about Safety
11
Chapter 1: Introduction
13
Why This Book Is Needed
13
What Do We Mean by Stable or Durable Glazes? IsThat Different from “Food Safe” Glazes?
14
The Seger Unity Formula and Its Relevance to Our Work
19
Conclusions
21
Chapter 2: Basics of Glazing and Firing
23
Safety First
23
Purchase and Storage of Glaze Chemicals
23
Weighing and Mixing
24
Glaze Suspension (Flocculents and Deflocculents)
28
Bisque Preparation
30
Bisque Firing
30
Cleaning
31
Glaze Resists
31
Applying glazes
32
Firing
34
Loading
34
Rate of Firing and Cooling
35
Summary
35
Chapter 3: Testing Glazes for Stability and Fit
37
Testing for Resistance to Acids
38
In-Studio Testing
39
Quantitative Testing by a Professional Testing Laboratory
40
Interpretation of Results
40
Testing for Resistance to Alkalis
43
Testing for Resistance to Thermal Shock (Clay/Glaze Fit)
44
Testing for Resistance to Knife Marking
46
Testing for Wear and Scratch Resistance
46
Testing for Chipping Resistance
47
Testing for Suitability for Use in a Microwave Oven
47
Summary
49
Chapter 4: Making a Stable Glaze
51
Rule 1. Have Enough Silica
52
Rule 2. Have Enough Alumina
53
Rule 3. Thoroughly Melt the Glaze
54
Rule 4. Use Moderate Levels of Colorants and Opacifiers
55
Guidelines for Improving Glaze Stability
58
Guideline 1
58
Guideline 2
59
Guideline 3
59
What about Limit Formulas?
59
Summary
60
Chapter 5: Fitting Glazes to Your Clay Body
61
Understanding Crazing, Dunting and Shivering
61
Crazing
61
Shivering or Dunting
62
Determining Clay/Glaze Fit for Your Materials
62
Understanding Dilatometer Measurements
63
Expansion Test Glazes and How to Use Them
67
Interpreting Calculated and Actual Measured Expansion Numbers
68
Are Calculated Expansion Numbers Useful?
70
Expansion Test Glazes
71
Summary
81
Chapter 6: Stoneware and Porcelain Glazes
83
Base Glazes
86
High Calcium Matte/Semimatte Glazes
86
General Purpose Glossy Base Glazes
92
Glossy Base Glaze 2
96
A Clear, Glossy Liner Glaze
97
A Zinc Semimatte/Glossy Base Glaze
97
Specialty Glazes
102
A Chrome/Tin Pink Glossy Glaze
102
Waxwing Brown
104
Waterfall Brown
106
A Cone 6 “Maiolica” Glaze
108
Alumina and Magnesia Matte Glazes
110
Summary
110
Chapter 7: Developing Your Own Glazes
Gloss versus Matte
111
Level of Transparency/Opacity
112
Solid color versus variegated glazes
112
Ron’s Approach to Glaze Development
113
John’s Approach to Glaze Development
116
Summary
118
Bibliography
119
Glossary
121
Postscript
Appendices
A: Recommended Materials
130
B: The Seger Unity Formula
C: Programs for Glaze Calculation
138
D: Testing Laboratories for Glazes
141
E: Firing Cycles for Electric Kilns
143
F: Materials Analyses
145
G: Glazes Used for Development of Rules
153
Rule 1 (Have Enough Silica)
153
Rule 2 (Have Enough Alumina)
155
Rule 3 (Thoroughly Melt the Glaze)
158
Rule 4 (Use Moderate Levels of Colorants or Opacifiers)
158
H: Useful References for Leaching Data
159
I: Limit Formulas for Cone 6 Glazes
162
Index
163