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ELECTRIC KILN CERAMICS
The American Ceramic Society
www.CeramicArtsDaily.org
Printed in China
ELECTRIC KILN
ZAKIN and BARTOLOVIC
This fourth edition of Electric Kiln Ceramics, Richard Zakin’s seminal work on
understanding and using the electric kiln to its fullest potential, has been completely
rewritten, reorganized, and expanded by Frederick Bartolovic. Hand picked by
Zakin to carry the title forward, Bartolovic has added new sections with step-by-step
instruction on forming and finishing pieces for electric firing, schedules for firing both
manual and computerized kilns, and has lavishly illustrated the book with completely
new images that highlight many of the most exciting results that are possible with
electric firing. Electric Kiln Ceramics has become the path countless professionals
and enthusiasts have followed to gain understanding and proficiency working with
electric kilns in the ceramics studio. From Zakin embracing and promoting the electric
kiln as a tool that yields exciting results to Bartolovic presenting it within the frame of
contemporary practice, technology, and aesthetics, Electric Kiln Ceramics promises
to continue inspiring and educating ceramic artists for generations to come.
FOURTH EDITION
A GUIDE TO CLAYS, GLAZES, AND ELECTRIC KILNS
CERAMICS
RICHARD ZAKIN and FREDERICK BARTOLOVIC
FOURTH EDITION
ELECTRIC KILN
A GUIDE TO CLAYS, GLAZES, AND ELECTRIC KILNS
CERAMICS
RICHARD ZAKIN and FREDERICK BARTOLOVIC
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ELECTRIC KILN CERAMICS
The American Ceramic Society
600 N. Cleveland Ave., Suite 210
Westerville, OH 43082
© 2015 by The American Ceramic Society, All rights reserved.
ISBN: 978-1-57498-341-8 (Paperback)
ISBN: 978-1-57498-576-4 (PDF)
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permission and reprint requests should be directed to Director, Publications, The American Ceramic Society, 600
N. Cleveland Ave., Westerville, Ohio 43082 USA.
Every effort has been made to ensure that all the information in this book is accurate. Due to differing
conditions, equipment, tools, and individual skills, the publisher cannot be responsible for any injuries, losses,
and other damages that may result from the use of the information in this book. Final determination of the
suitability of any information, procedure or product for use contemplated by any user, and the manner of that
use, is the sole responsibility of the user. This book is intended for informational purposes only.
The views, opinions and findings contained in this book are those of the author. The publishers, editors,
reviewers and author assume no responsibility or liability for errors or any consequences arising from the use
of the information contained herein. Registered names and trademarks, etc., used in this publication, even
without specific indication thereof, are not to be considered unprotected by the law. Mention of trade names of
commercial products does not constitute endorsement or recommendation for use by the publishers, editors or
authors.
Publisher: Charles Spahr, Executive Director, The American Ceramic Society
Managing Director and Editor: Sherman Hall
Design and Graphic Production: Melissa Bury
Cover Image: Jason Green
ii
CONTENTS
Foreword by Linda Arbuckle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii.
Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv
Introduction
What Is an Electric Kiln? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
A Brief History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Current Technologies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Chapter 1: Clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Unique Properties of Clay. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Drying and Shrinkage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Firing and Shrinkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.1: Clay Bodies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Clays Used in Clay Bodies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Non-Clay Materials Used in Clay Bodies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Important Attributes of Clay Bodies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Plasticity | Working Strength | Body Color | Maturity | Clay Body Absorption |
Clay Body Texture | Resistance to Warping | Intended Use
Clay Body Firing Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Low-Fire Bodies (Cone 06 to 1) | Mid-Fire Bodies (Cone 2 to 7) |
High-Fire Bodies (Cone 8 and Above)
Common Clay Body Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Earthenware Bodies | Stoneware Bodies | Porcelain Bodies | Porcelaneous Bodies
Unconventional Clay Bodies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Self-Glazing Clay Bodies | Low-Clay-Content Bodies | Colored Clay Bodies |
Highly Active Fluxes in Clay Bodies | Heavy Aggregate Bodies | Paper Clay Bodies
1.2: Testing and Mixing Clay. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Choosing a Clay Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Forming Methods |Firing Temperature | Clay Body Color and Texture |
Character and Purpose of the Pieces
Mixing Clay Bodies in the Studio. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Mixing Small to Medium Batches | Mixing Medium to Large Batches
Material Availability and Substitutions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Commercially Prepared Clay Bodies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
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ELECTRIC KILN CERAMICS
Testing Clay Bodies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.
Working Character Test
Absorption Test
Informal Clay Body Absorption Test | Computational Clay Body Absorption Test |
Appropriate Absorption Rates
Shrinkage Test
Appropriate Rates of Shrinkage
Slumping and Warping Test
1.3: Forming Clay. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Fundamentals of Building. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Aging the Clay | Wedging | Tools for Forming | Joining Two Pieces of Clay
Ceramic Forming Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Pinch Forming
Pinching a Cylinder Form | Building a Large Pinch Form
Coil Building
Coiling Clay to Make a Cylinder
Solid Forming
Hollowing a Solid Form
Slab Building
Throwing a Slab | Slab Building a Cylindrical Form | Working with the Cylinder |
Turning the Cylinder into a Vessel Form | Turning the Cylinder into a Closed Form
Throwing on the Potter’s Wheel
The Process | Centering | Opening up the Form | Pulling up the Walls
Thrown and Altered Forms
Ovalizing a Thrown Cylinder
Extruding
Forming Clay with Molds
Drape Molds | Using a Plywood Drape Mold to Create a Plate | Press Molding
Slip Casting
Casting Slip | Casting a Piece with Slip
RAM Pressing: An Industrial Forming Method
Making a Plaster Mold
Mixing Plaster | Making a Simple One Piece Mold | Making a Simple Two Piece Mold
1.4: Clay Finishes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Unadorned Clay Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Stained Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Materials for Creating Stained Surfaces | Stained Surface Applications
Slips and Engobes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Slips | Engobes | Applying Slips and Engobe | Shrinkage in Slips and Engobes |
Calcining Clay for Slips and Engobes | Exploiting Cracking and Flaking | Gritty Slips
Vitreous Slips and Engobes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Commercial Underglazes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Applying Commercial Underglazes | Underglaze Chalks and Pencils
Terra Sigillata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Making Terra Sigillata | Testing the Sigillata | Using Terra Sigillata
iv
1.5: Developing Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Altering Surfaces and Developing Texture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Stamping | Carving | Sprigging | Sprig Molded Imagery | Inlaid Sprig Molded Forms |
Combining Sprigged, Stamped and Engraved Imagery | Combining Manipulated
Surfaces with a Slip or Glaze | Finishing a Piece Using the Intaglio Method
Image Creation Strategies Using Commercial Underglazes . . . . . . . . . . . . . . . . . . . . . . . . . 76
Underglaze Chalks and Pencils
Applying Slips, Engobes and Commercial Underglazes. . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Testing Image Creation Strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Develop a Painterly Surface | Slip Trailing | Sgraffito | Mishima
Chapter 2: Glaze. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85.
Glaze Makeup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Character of Glazes Fired in Electric Kilns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85.
Light Reflection—Shiny, Matte, Dry Surfaces | Light Transmission—Transparency,
Translucency, Opacity | Visual Texture | Utility and Durability | Color
Low-, Mid-, and High-Fire Glazes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Commercially Prepared Glazes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Low-Fire Glazes | Mid-Fire Glazes | High-Fire Glazes
2.1: Categorizing Glazes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Classifying Glaze by Significant Ingredients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Alumina | Boron | Calcium/Magnesium | Clays: Light and Dark | Feldspar and Frit |
Lithium/Spodumene | Silica | Slip Glazes | Strontium | Tin | Titanium | Wood Ash |
Zinc | Zirconium
Classifying Glaze by Opacity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Classifying Glaze by Visual Texture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Transparent | Opaque | Translucent
Strategies to Encourage Visual Textures | Rough Surfaced, Curdled Glazes |
Smooth Surfaced (Industrial) Glazes
Glossy, Matte and Dry Surfaces
Shiny Glazes | Satin Glazes | Matte, Dry, or Stony Glazes
Low Viscosity Glazes
Crystalline Glazes
Classifying Glaze by Intended Use or Purpose. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
Food Containers | Outdoor Use | Sculpture
2.2: Evaluating Glaze Recipes and Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
Glaze Attributes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
Color | Surface | Visual Texture | Light Transmission | Glaze Flow |
Crawling and Crazing | Shivering | Durability | Suitability of Task
Testing Glazes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Testing Commercially Prepared Glazes | Testing Glazes Made in the Studio |
Developing Glaze Recipes on Your Own
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ELECTRIC KILN CERAMICS
2.3: Glaze Color. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
Clay as Color. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
Oxide Colorants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Oxide Colorant Chart
Commercially Prepared Stains. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Using Stains
2.4: Glaze Mixing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Studio Prepared Glazes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
The Learning Process | Ordering Materials | Clays | Frits and Feldspars | Other Materials |
Opacifiers | Colorants | Stains | Tools for Weighing and Mixing Glazes
Mixing Glaze in the Studio. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
Sedimenting
2.5: Applying Glazes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
Commercial Glazes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
Firing Prepared Surfaces | Toxicity
Application Strategies for Commercial Low-Fire Glazes (Cone 05 or 04) . . . . . . . . . . . . . . 125
Commercial Mid-Fire Glazes (Cone 5 or 6). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
Mid-Fire Glaze Character | Mid-Fire Glaze Types
Using Commercial and Studio-Made Glazes on the Same Piece. . . . . . . . . . . . . . . . . . . . . 127
Applying Studio-Made Surfaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
Dipping
Dipping with tongs
Pouring
Brushing
Using a Brush to Apply Linear Imagery | Using a Brush to Apply a Textured Surface |
Brush Character
Spraying
Glazing a Piece Using a Sprayed Application | External Mix Sprayers | Atomizers |
Spray Booths
Masking and Resist Materials
Slip-Trailing or Tracing
Application Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
Simple Glaze Application
Complex Glaze Application Strategies
Multiple Layer Glaze Application | Resist Glazing | Combining a Dipped Base Glaze
with Linear Brush-Applied Imagery | Combining Brush-Applied Texture with Poured
Imagery and Sprayed Clear Glaze | Combining Terra Sigillata and Glaze Applications |
Combining Clay-Formed Imagery with Glazes | Combining Engraved and Glazed
Imagery | Engraving into a Base Color | Intaglio Glazing | Combining Relief Imagery
with Glazes | Carved and Intaglio Glazed Imagery | Engraved, Stamped, and
Sprigged Imagery with Intaglio Glazing
Testing a Complex Glaze Application
vi
2.6: Glaze Materials Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
Safety When Preparing and Applying Glazes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
Materials Safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
Insuring Finished Fired Work is Safe to Use | Material Toxicity |
Substitutes for Toxic Materials | Encapsulated Stains
2.7: Glaze Faults. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
Crawling
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
Avoiding Crawling | Achieving Crawling
Crazing
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Avoiding Crazing | Achieving Crazing
Running
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
Avoiding Running | Achieving Running
Shivering
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
2.8: Overglazes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
Lusters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
Decals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Laser Toner Decals | Full Color Decals
China Paints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
Using Different Overglazes Together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
Chapter 3: The Electric Kiln. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
Firing Choices for the Kiln . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
Firing by Sight | Firing with a Kiln Sitter | Firing with Computer Controllers
Temperature Measuring Devices: Pyrometers and Thermocouples. . . . . . . . . . . . . . . . . . . 166
3.1: Kiln Designs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
Design and Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
Overall Design
Electrical Components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
Computer Controlled Interfaces | Manual Control Switches | Kiln Elements |
Kiln Wiring | Relays | Electrical Phasing and External Connections
Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
Insulating Bricks | Brick Alignment and Wall Thickness | Insulation | Metal Shell |
Kiln Floor | Kiln Roof and Door | Door Hinges | Peep Hole
Purchasing an Electric Kiln. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
Choosing Front-Loading or Top-Loading
Front Loading Kilns | Top-Loading Kilns
Choosing Computerized Interface or Manual Switches
Characteristics Shared by Electric Kilns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
Kiln Walls | Kiln Elements | Kiln Switches and Wiring Harness
Electric Service—Voltage and Phase. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
What your Supplier Must Know
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ELECTRIC KILN CERAMICS
3.2: Loading the Kiln . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
Firing—Basic Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
Controlling Heat
Loading the Electric Kiln . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
Kiln Furniture | Kiln Wash | Kiln Wadding | Preparing the Kiln for Loading
Building the Kiln Shelf Structure
Building a Structure with Kiln Furniture
Heat Work: Measurement and Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
Pyrometric Cones
Cone Numbering | Cone Charts
Cone Packs
Making a Wet Clay Cone Pack | Sighting and Placing the Cone Pack
3.3: Firing the Kiln. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
Bisque Firing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
Preparing the Bisque Firing
Preheating or Candling
Manual Kiln Preheat | Digital Interface Kiln Preheat
Manual Bisque Firing Cone 06
Computer Controlled Bisque Firing Program, Cone 06
Finish Firing or Glaze Firing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
Preparing for the Glaze Firing | Manual Glaze Firing Cone 04–10 |
Computer Controlled Glaze Firing Programs, Cone 04–10
Cooling Electric Kilns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
Cooling Rates at the End of the Firing | Cooling the Kiln by Down Firing |
Opening the Kiln Door | Taking Ware from the Kiln
Important Stages of the Firing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
Quartz Inversion | Cristobalite | Dunting or Cooling Cracks
Multiple Firings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
3.4: Test Kilns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
What to Look for in a Test Kiln . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Placing the Test Kiln. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Uses for the Test Kiln. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Firing a Computerized Test Kiln . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Firing a Manual Test Kiln. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
200
201
202
202
202
203
Firing Down
3.5: Kiln Maintenance and Repair. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Repairing a Sagging Element. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cleaning the Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Replacing Broken Elements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A Quick Temporary Weld
viii
204
204
204
205
Replacing a Thermocouple or Pyrometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Switches and Relays. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Kiln Roof
........................................................
Kiln Floor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Kiln Wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wiring
........................................................
When the Kiln Must be Discarded. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
205
205
206
207
207
207
207
3.6: The Studio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
Setting Up a Studio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
The Work Space | Economy Class—An Inexpensive Studio
Studio Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
Basic Furnishings | Small Tools for General Use | Small Useful Tools for
the Hand Builder | Tools for Throwing | Tools for Glaze Formulation
and Application | Tools for Testing Ceramic Formulations
Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
Clay Mixers | Pug Mill | The Potter’s Wheel | Slab Rollers | Ball Mill |
Air Compressor | Spray Booth
Sprayers
External Mix Sprayer | Internal Mix Sprayer | Atomizer
Scales and Balances
3.7: Studio Safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
Kiln Safety
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
Electrical Safety | Fire Safety | Viewing the Kiln Interior During Firing
Respiratory Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
Respirators | When to Replace Filtering Cartridges
Disposable Safety Garments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
Ventilation
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
Dust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
Cleaning Strategies
Studio Equipment Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
Bench Grinders | Clay Mixing Equipment
Appendix 1: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
Appendix 2: Ceramic Recipes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
Appendix 3: Resources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
Appendix 4: Glossary of Terms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
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ELECTRIC KILN CERAMICS
1.2 Testing and Mixing Clay
Finding the right clay body often involves mixing several small batches of different clays and then testing
them. There are a number of tests outlined in this section to help you decide what clay body will be right
for you. These tests can also be used on commercial clay bodies. Once you decide upon a clay body then you
mix larger amounts of it up or find a supplier who might mix it for you.
Sunshine Cobb, Narrow Traskets, 14 inches long, mid-range red clay, slab base and coil built, cone 3, 2014. Photo by artist
Choosing a Clay Body
Choosing the right clay body depends on the
character and purpose of the piece one intends to
build. The forming methods you employ, the firing temperature, body color and texture you hope
to achieve, and compatibility with glazes will also
dictate what clay body makes the most sense. As you
gain more experience working with clay, often so
too do your ideas about what is important in a clay
body. Consider these characteristics as you decide
upon what may be right for you.
Forming Methods
Throwing bodies should be plastic, strong, and
resistant to collapse under the stress of throwing.
They should not contain highly coarse materials or
the thrower’s hands will suffer. Handbuilding bodies
may be slightly less plastic but should be quite strong.
They may contain coarse particles, which discourage
warping and shrinkage and increase strength.
Firing Temperature
The body and glaze must be compatible in firing
temperature. Most ceramists start by choosing to
24
Joseph Pintz, Red-handled Gardening Tools, 30 inches wide,
hand-built earthenware with terra sigillata, glaze, cone 04, 2013.
Pintz states, “While in graduate school at the University of NebraskaLincoln, I began working with clay from a local brick manufacturer
(Endicott Clay Products, Endicott, NE). Their ‘potting clay’ had
great working characteristics—plasticity, density, and a rich terra
cotta color. It also had the benefit of not being over-processed so it
retained it coarse texture. With a few minor alterations, the basic clay
that was sent down the conveyor belt to make bricks became the
backbone of my earthenware claybody.” Photo by Jeffrey M. Bruce
Clay
Joseph Pintz, nesting bowl set, 12 inches in diameter, handbuilt earthenware, slip, glaze, cone 03, 2013. The color of
Pintz’s clay plays an important role for the overall character of
these functional forms. Photo by Jeffrey Bruce
work at a particular firing temperature, then match
their clay bodies and their glazes to that temperature.
Bryan Hopkins, pendants, varying dimensions, low-fire
The clay body must not mature at a point lower
translucent porcelain, 2014. These pendants are made from
clay bodies Hopkins had been formulating for some time. The
than the maturation point of the glazes. If it does,
recipes are included in Appendix 2, but Hopkins recommends
the body may melt or deform when the glazes are
thorough testing on well coated kiln shelves. These bodies
were developed to be single fired, and they require no
fired to maturity. Furthermore, it can be dangerous
glaze. The translucence difference on the colored pieces is
to use a glaze that matures at a point lower than the
due simply to stain. With the addition of 3% stain there is a
significant gain in opacity. Photo by artist
maturation point of the clay body. If this happens,
the glazes will not fit the body; in this situation the
brittle glazes will not be supported by the body and may chip and most likely craze as well.
Some suppliers label clay bodies as appropriate for a very wide range of firing temperatures (e.g. for
cones 3–7). Clay bodies just do not work this way—they mature at a specific temperature and are best used
at that temperature.
Body Color and Texture
There are those who prefer dark clay bodies because they look rich and natural. Others prefer light-colored
bodies because they feel that glaze color in the electric firing is likely to be more lively when applied over a
light-colored body. If you use translucent or transparent glazes, you will get the best results when you apply
them over light-colored bodies (or you may apply a cover coat of light-colored slip over a darker body to
provide a light-colored base for the glazes).
You have the choice of using bodies with fine or coarse textures. Delicate pieces suggest the use of finetextured clay bodies, while less delicate work suggests the use of coarse bodies. Those who desire an earthy,
natural, bold surface will likely prefer a coarse body. Other ceramists associate work in oxidation with precision and elegance; they may prefer a fine-textured body. Those ceramists who work with carved imagery
will find that coarse particles interfere with the carving process.
Character and Purpose of the Pieces
Utilitarian pieces (especially tableware) require dense and highly durable bodies that are easily cleaned. The
requirements for decorative or sculptural pieces are not as exacting and many who make pieces of this sort
prefer to use bodies that are less dense.
25
ELECTRIC KILN CERAMICS
Mixing Clay Bodies In the Studio
Mixing clay in the studio is a relatively simple process. Small batches can be mixed by hand and do not
require any special equipment for mixing. Larger batches of clay will require a clay mixer, a machine designed to churn the components of a clay body with water until it reaches a consistency suitable for use.
Clay mixers are large heavy machines which also require some form of ventilation around them to remove
dust generated during the mixing process. For this reason many contemporary ceramists do not mix their
own clay but rely on a commercial clay supplier. This makes sense in terms of saving studio space needed
for mixing equipment, as well as safety and convenience. It is, however, useful to know how to make clay
bodies in both large and small batches.
Mixing Small to Medium Batches (500 to 20,000 Grams)
There may come a time when you wish to test a new clay body recipe or to make a small amount of a special
clay body, such as a porcelain or a grit-loaded clay body. The mixing process described here is not difficult.
It is fairly quick, not terribly demanding, and does not require expensive, complex, or dangerous machinery.
1
Measuring the specific amount of each
ingredient.
4
Dry mixture is placed on a non-porous
surface.
26
2
Measured ingredients get placed in
another bowl.
5
An atoll structure is formed with the dry
materials.
3
Once all ingredients have been added
they are dry mixed by hand.
6
Water is poured into the central moat
depression.
Clay
7
Mix water into the dry materials by
hand.
8
Wedge the clay to thoroughly mix the
dry materials and water.
9
A completed test batch of a red
stoneware body.
1. Weigh all the clay body materials.
2. Mix the dry materials carefully together.
3. Place the materials on a large water-resistant surface such as a large piece of linoleum or a stainless
steel table.
4. Form the powdered clay into a mound in the center of the mixing area.
5. Form the mound into an atoll structure; a central mound surrounded by a circular doughnut-shaped
wall. This creates a moat-like trench around the central mound. You are now ready to add water. To
get a workable consistency clay body you will need on average about 30% (+/-5%) of the weight of the
clay.
6. Pour the water into the moat-like trench and let it sit for a few minutes. If water leaks through the wall
of the structure, press some extra powdered clay against that section.
7. Push the dry clay at the top of the doughnut-shaped wall into the water in the moat. Do the same with
the clay in the central mound. After a few minutes of this action, the clay and the water should be fairly
well mixed.
8. Allow this mixture to sit for a few minutes, then begin wedging the clay body.
Note: When wedging, it’s a good idea to pass a wire through the clay several times. Separate the pieces,
shuffle them, and wedge again to ensure a homogenous mixture.
9. Make adjustments if necessary. Wait until the end of the mixing process before making any adjustments. Only then will you know if you need to make them. If the clay is too dry, use a spray bottle to
slowly add a bit more water, distributing the water evenly. If the clay is too wet, let it air dry until it
reaches the consistency you desire. Make notations so you can adjust appropriately next time. Place
the clay body in a plastic container. If possible let the mixture rest for a week or so before using it. This
aging allows the bacteria in the clay body to multiply. These bacteria are not harmful—in fact they
encourage a workable clay body. Clay bodies which have aged are usually much more plastic than ones
that have not.
Note: Mixing clay inevitably involves creating a considerable amount of dust, as clay particles are some of the
smallest particles known to man and stay airborne for up to 48 hours, Use ventilation or respiratory precautions,
and refer to Section 3.7 Studio Safety for more detailed safety information.
27
ELECTRIC KILN CERAMICS
Mixing Medium to Large Batches (100 to 200 pounds)
Mixing larger batches of clay is a physically demanding activity often requiring the moving of 50 pound bags
of raw materials. It also requires a clay mixer which additionally necessitates following manufacturer safety
precautions and employing respiratory protection. The mixing process described below is fairly quick and
produces enough clay to last a while depending on your production level.
1. Weigh all the clay body materials and place them into a large container.
2. Mix the dry materials together so each material becomes dispersed evenly.
3. Measure out your water and place it in your clay mixer. Through smaller batch testing you should know
the exact amount of water needed. It should be about 30% (+/-5%) of the weight of the clay.
4. If it is possible to add dry material to your mixer while it is running then turn your clay mixer on. Otherwise you will need to add material to your mixer through turning it off, adding dry material, then turning
the mixer back on again.
28
A Soldner clay mixer ready for use.
About 25–30% of your overall recipe
weight should equal the weight of water
you will need. Measure the water out first.
Add water to the clay mixer.
Measure out the dry ingredients.
Add dry ingredients to a larger
container designated for dry mix.
Mix all the dry ingredients thoroughly.
Clay
Add dry ingredients to the water in the mixer. The mixer
should be running as you add material. Add material one
scoop at a time. Make sure you follow safety precautions
around the mixer.
Once all dry mix has been added let the mixer run for 15–30
minutes. If clay is too wet you will need to add more dry mix. If
too dry you will need to add water to the clay mixer. Add water
very slowly if needed.
5. It is better to slowly add your dry mix to the water as opposed to adding all the dry mix at once. Slowly
introducing the dry materials allows you to control the consistency. Depending on what you are intending to build with the clay you may want a wetter or dryer mixture.
6. Once you have used all your dry material and achieved the correct consistency allow the mixer to run for
an additional 15–30 minutes. This will insure all the materials are thoroughly mixed.
7. Unload the mixer. Place the clay body in an airtight container. If possible let the clay rest for a week or
so before using it. This allows the clay to age becoming more plastic and workable.
8. Clean the clay mixer. This may be one of more time consuming parts of the mixing experience, but it is
important to thoroughly clean the mixer so if you mix a different kind of clay next time the new body
will not be contaminated in any way.
9. After using the clay take notations so you can adjust proportions of water to clay if needed next time.
Notes on mixing large batches: Clay mixers can be dangerous if not used properly. Follow the manufacturer’s
directions and never bypass safety switches or place yourself in close proximity to the mixer when it is running. If
clay is too dry when mixing add water very slowly into the mix. Clay particles are so fine that they tend to absorb
additional moisture in the first 24 hours after being mixed. For this reason I usually suggest mixing slightly on
the wetter side knowing that the clay will stiffen up a bit after mixing.
Material Availability and Substitutions
The availability of materials is a particular problem for both suppliers and ceramists. Although many materials are available nationally, some materials are only available regionally. Materials are also sometimes simply
not available because a supplier may be out of them, or in rare instances they may not be being produced
any longer. The reality is that these materials are dictated by the larger ceramics industry, and not by potters and artists (who make up a very small percentage of the entities using these materials). In cases where
substitutions must be made, the supplier may be able to suggest useful alternatives. Always test materials
you are unfamiliar with before committing to larger batches.
29
ELECTRIC KILN CERAMICS
Commercially Prepared Clay Bodies
Blake Williams, Nourish, porcelain, wire, antique kitchen chair,
36 inches tall, 2010. Williams uses Laguna Frost porcelain, a
commercial clay body which she sometimes adds Spectrum
stains into to achieve color. She then fires to cone 6, holding
there for 20 minutes to produce a sheen. Photo by Tim Thayer
Blake Williams, Nourish, porcelain, wire, antique kitchen chair,
2010. Photo by Tim Thayer
30
Ceramists starting out in clay and those with small
studios may find that their needs are met best by using clay bodies mixed by a clay producer and housed
in a ceramics supply house. In this scenario you can
usually get it delivered or pick it up, and it comes
already mixed and bagged. Generally, suppliers sell
a standard line of prepared clay bodies and they will
probably suggest that you use one of these. These
bodies are modest in price and are readily available.
To satisfy the ceramics market, supply houses
can usually contact their clay producer and order
customized clay bodies. Though these custom clay
bodies may cost a bit more, they are much more
likely to fill your specific requirements. (Usually
minimum amounts of at least 500 or 1000 pounds
are required for ordering custom clay bodies.) In
this scenario it is important that you check each new
shipment and make a few pieces or test tiles from the
clay body as soon as you take delivery as one batch
to the next may have slight differences.
If you do order a custom clay body ask where
the clay is mixed. It may be possible to visit the clay
manufacturer, and observe the mixing process. While
you may not know exactly what is going on, you can
draw some general conclusions. If the atmosphere is
confused, disorganized, or marked by lack of interest,
find another supplier. In a good supply house, great
attention will be paid to detail to ensure that the clay
bodies are reliable. Weighing, mixing, and cleaning
must be carried out with attention and care. Materials
must be on hand, the weighing of materials must be
accurate, mixing must be thorough, and the mixing
machinery must be cleaned after mixing one clay
body type before mixing another. These are tedious
and demanding jobs; good suppliers make sure they
are done well and that no corners are cut.
While price is a factor, the expense of the clay
body is often small compared to the ceramist’s
investment of time and effort. The most important
considerations in choosing a clay body supplier are
support services and quality.
Note: You are free to ask your supplier to make your
clay bodies from any of the clay body recipes in this book.
Clay
Testing Clay Bodies
It is important that you know how to test clay
bodies to understand the different attributes
it might have. This is especially true if you
purchase clay bodies from a ceramic supplier.
While the clay body is likely to work for various
purposes, testing it allows you to know how
workable it is, how much water it will absorb,
and how much it will shrink in the firing.
Working Character Test
This is a measure of the way the clay body can
be manipulated. This is mostly a subjective
matter. Your opinion of a clay body’s working
character will be influenced by the way you
wish to work with it. If you intend to create
your forms on a pottery wheel, you may well
want a very plastic and bendable clay body.
On the other hand, if you are hand forming
large complex pieces, you will want a tough,
durable clay body that resists cracking when
you manipulate and fire it.
To test for working character, roll out a
coil of clay about 1 centimeter thick and 14
centimeters long. Bend it into the shape of
a script e. If the clay body doesn’t crack at
the bend, it has a good working character. If
it cracks at the bend, the working character
of the body is poor. If you form your work
on the potter’s wheel, continue your test by
throwing a sample of the clay on the wheel. If
you hand form your pieces, make a test slab,
curve it, and paddle it to see how it reacts to
this treatment.
Absorption Test
One of the things you need to know about
a clay body is the rate it absorbs moisture
at your firing temperature. Most fired clay
bodies absorb some moisture but the rate of
absorption can vary a good deal. Following
are two procedures for testing absorption. The
first is an informal method that only takes a
minute or two; the second is far more accurate
but takes more time.
These two clay coils show the workability of the clays. The dark
clay is a red stoneware clay just mixed compared to an aged
porcelaneous body. Notice the cracks in the red stoneware coil
versus the smooth quality of the white body.
Kevin Lyles, Still Waters Run Deep, 18 inches tall, hardware cloth
dipped in paper clay, cast bronze, cast glass, embroidery thread,
aluminum, cone 05, 2009. Experimental processes such these
require extensive testing with your materials. Photo by artist
31
ELECTRIC KILN CERAMICS
Informal Clay Body Absorption Test
Lay a light coating of water on an unglazed finish fired piece. The base of a fired pot will do nicely if it is
completely free of glaze.
The object of the test is to observe the rate of absorption. If the water is absorbed into the clay body in
a span of 20 to 40 seconds, the body is highly absorbent. If the water is absorbed in a span of two to three
minutes, the body is moderately absorbent. If absorption takes longer than two or three minutes, the body
is mature. If the water stays on the surface without any absorption, the body has little or no absorption.
Computational Clay Body Absorption Test
This highly accurate test is carried out on a test tile made especially for the purpose. The test tile should be
fired to maturity and not glazed.
1. Make a test tile 2 × 2 inches or larger and fire it. Remove the tile from the kiln as soon as it cools.
2. Weigh the tile and write the weight on it (use a pencil or a fiber-tipped pen filled with indelible ink).
3. Immerse the tile in water for 24 hours or longer.
4. Remove the tile from the water and use a sponge and a towel to remove the surface water.
5. Weigh the tile again.
6. Subtract the original weight from the weight of the immersed tile.
7. Divide the difference by the original weight.
8. Move the decimal point two places to the right. The result is the percentage of absorption.
Example
Weight of the tile after immersion: 9.8 grams
Weight of the tile when drawn from kiln: 9.4 grams
0.4 ÷ 9.4 (original weight) = .042
After moving the decimal point two places to the right, the result is 4.2, meaning the absorption rate of
the tile is 4.2%.
Appropriate Absorption Rates
While the absorption rate of a clay body is an objective measurement, subjective judgment plays a very
important part; as you must decide what is appropriate for your work. There is no single appropriate absorption rate for all clay bodies or for all types of ceramic work. If you work in porcelain you will probably
want a very low absorption rate. If you are working in the low fire, you cannot hold your clay bodies to such
exacting standards.
The intended purpose of the work also plays an important part. If you make utilitarian pieces you may
want a low absorption rate. However, if you are making sculptural or decorative pieces, a low absorption
rate might not be appropriate. Below are listed various clay body types and a judgment of their appropriate
absorption rates.
Clay Body Type
Appropriate Absorption
low fire
8% to 12%
stoneware food containers
4% to 5%
decorative stoneware 5% to 8%
porcelain 1% to 3%
sculpture bodies 10% to 20%
32
Clay
Measuring a 10 centimeter line on the
test tile allows for an easy conversion
to percentages.
Mark the 10 centimeter line at 90° at
each end.
Fire your test tile and re-measure the line.
In this case the tile shrank about 14%.
Shrinkage Test
Clay bodies shrink in both drying and firing. As is the case with absorption, appropriate shrinkage rates
vary a great deal. No ceramist likes a high rate of shrinkage but if you are working with a fine-grained clay
body with a low absorption rate, such as a fine-grained white body, you may have to accept a high rate of
shrinkage as inevitable.
1. Make a test tile 14 × 4 × 0.7 centimeters of a clay body with water content that’s typical of your clay body.
2. Draw a line along the length of the tile and mark off 10 centimeters.
3. Let the tile dry and fire it to the desired temperature.
4. Measure the new length of the line.
5. Subtract the length of the new line from 10 centimeters (the original length of the line).
6. Divide this figure by 0.1 to find the percentage of shrinkage.
Appropriate Rates of Shrinkage
As is the case with absorption, the ceramist must decide what shrinkage rate is appropriate. Appropriate
shrinkage rates can and should vary a great deal. A dense porcelain is likely to have a very high shrinkage
rate, while a sculpture body fired to a less dense state will have a low shrinkage rate.
The intended purpose of the work also plays an important part. The ceramist who works with very large
pieces that cannot stand the strain of a high rate of shrinkage will have to work with coarse, highly absorptive bodies that don’t shrink very much. The ceramist who creates utilitarian ware may well decide that a
low absorption rate is necessary and will put up with a high shrinkage rate.
Below are various clay body types and a judgment regarding their appropriate shrinkage rates.
Clay Body Type
Appropriate Shrinkage
low fire
8% to 12%
stoneware food containers
12% to 15%
decorative stoneware
10% to 14%
porcelain
14% to 20%
coarse bodies
5% to 8%
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ELECTRIC KILN CERAMICS
Placed in the kiln this newly mixed clay body is ready to be
tested for slumping.
Though the color of this clay body is a pleasant deep red when
finish fired, it has slumped quite a bit.
Slumping and Warping Test
Bodies that are mature or over-fired often distort or
slump in the fire. If the body has a very low absorption rate and it slumps a great deal, the body may be
over-fired. In a mature clay body a small amount (as
much as a ¼-inch) of slumping is inevitable, but if
the clay slumps and warps more than that, you may
wish to find a clay body that is more appropriate for
your firing temperature.
This is an important test and a very simple one.
1. Make a test tile 4 inches long and let it dry completely.
2.Place refractory supports (such as kiln posts)
under each end of the tile so it is free to slump
in the middle.
3. Fire the tile to the desired temperature (the tile
need not be bisque fired).
4. Measure its rate of slumping in the middle. If
the amount of slumping is over a ¼-inch, forms
made with this body are likely to slump or warp.
Richard Notkin, Heart Teapot—Petrol Hostage, stoneware clay, approximately 12 inches long, 2013. Photo by Tom Ferris
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ELECTRIC KILN CERAMICS
The American Ceramic Society
www.CeramicArtsDaily.org
Printed in China
ELECTRIC KILN
ZAKIN and BARTOLOVIC
This fourth edition of Electric Kiln Ceramics, Richard Zakin’s seminal work on
understanding and using the electric kiln to its fullest potential, has been completely
rewritten, reorganized, and expanded by Frederick Bartolovic. Hand picked by
Zakin to carry the title forward, Bartolovic has added new sections with step-by-step
instruction on forming and finishing pieces for electric firing, schedules for firing both
manual and computerized kilns, and has lavishly illustrated the book with completely
new images that highlight many of the most exciting results that are possible with
electric firing. Electric Kiln Ceramics has become the path countless professionals
and enthusiasts have followed to gain understanding and proficiency working with
electric kilns in the ceramics studio. From Zakin embracing and promoting the electric
kiln as a tool that yields exciting results to Bartolovic presenting it within the frame of
contemporary practice, technology, and aesthetics, Electric Kiln Ceramics promises
to continue inspiring and educating ceramic artists for generations to come.
FOURTH EDITION
A GUIDE TO CLAYS, GLAZES, AND ELECTRIC KILNS
CERAMICS
RICHARD ZAKIN and FREDERICK BARTOLOVIC