Clay. A Studio Handbook PDF
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Clay A Studio Handbook Related Titles published by The American Ceramic Society Out of the Earth Into the Fire:A Course in Ceramic Answers to Potters’ Questions II Materials for the Studio Potter, Second Edition Edited by Ruth C. Butler Mimi Obstler 01998, ISBN 1-57498-085-8 02000, ISBN 1-57498-078-5 Great Ideas for Potters II The Extruder Book Edited by Ruth C. Butler Daryl E. Baird 01998, ISBN 1-57498-068-8 02000, ISBN 1-57498-073-4 Answers to Potters’ Questions Creative Ideas for Clay Artists Edited by Barbara Tipton Edited by Anderson Turner 019 90, ISBN 0-934706- 10-7 02001, ISBN 1-57498-122-6 Great Ideas for Potters Barrel, Pit, and Saggar Firing Edited by Barbara Tipton Edited by Sumi von Dassow 01983, ISBN 0-934706-09-3 02001, ISBN 1-57498-127-7 Potter’s Wheel Projects Glazes and Glass Coatings Edited by Thomas Sellers Richard A. Eppler and Douglas R. Eppler 01968, ISBN 0-934706-04-2 02000, ISBN 1-57498-054-8 Decorating Pottery The Magic of Ceramics F. Carlton Ball David W. Richerson 01967, ISBN 0-934706-05-0 02000, ISBN 1-57498-050-5 Brush Decoration for Ceramics Marc Bellaire Boing-Boing the Bionic Cat Larry L. Hench, Illustrated by Ruth Denise Lear 019 64, ISBN 0-934706-02-6 02000, ISBN 1-57498-109-9 Ceramic Projects Edited by Thomas Sellers Setting up a Pottery Workshop 01963, ISBN 0-934706-08-5 CO-published by The American Ceramic Society, Westerville, Ohio, USA and A&C Black, Throwing on the Potter’s Wheel London, England Thomas Sellers Alistair Young 01960, ISBN 0-934706-03-4 01999, ISBN 1-57498-106-4 Underglaze Decoration Glazesf or the Craft Potter, Revised Edition Marc Bellaire CO-published by The American Ceramic Society, 01957, ISBN 0-934706-01-8 Westerville, Ohio, USA and A&C Black, London, England Copper Enameling Harry Fraser Jo Rebert and Jean O’Hara 019 98, ISBN 1-57498-076-9 01956, ISBN 0-934706 For information on ordering titles published by The American Ceramic Society, or to request a ceramic art publications catalog, please contact our Customer Service Department at 614-794-5890 (phone), 614-794-5892 (fax),<customersrvc @,acers.org> (e-mail), or write to Customer Service Department, 735 Ceramic Place,W esterville, OH 43081, USA. Subscribe to Clayart! Clayart is the “electronic voice of potters worldwide.” Subscriber-initiated discussions range from questions/answers on materials and techniques to business advice and philosophical debate, sponsored by The American Ceramic Society.Visit the website and subscribe at <www.ceramics.org/clayart>. Visit our on-line bookstore at <www.ceramics.org> A Clay Studio Handbook Vince Pitelka Published by The American Ceramic Society 735 Ceramic Place Westerville, Ohio 43081 www. ceramics. org The American Ceramic society The American Ceramic Society 735 Ceramic Place Westerville, Ohio 43081 www.ceramics.org 0 2001 by The American Ceramic Society. All rights reserved. Published 2001. Printed in the United States of America. 05 04 03 02 01 5 4 3 2 1 Executive Director and Publisher Developmental Editor W. Paul Holbrook Sarah Godby Senior Director, Publications Marketing Assistant Mark Mecklenborg Jennifer Brewer Acquisitions Production Manager Mary J. Cassells John Wilson ISBN: 1-57498-090-4 Design by settingpace, Cincinnati, Ohio. Photography by Amanda Williams andVince Pitelka. Main cover image: Paddle-and-anvil forming method. Photograph by Amanda Williams. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording, or otherwise, without the written permission from the publisher, except by a reviewer, who may quote brief passages in review. Authorization to photocopy for internal or personal use beyond the limits of Sections 107 and 108 of the U.S. Copyright Law is granted by The American Ceramic Society, provided that the appropriate fee is paid directly to the Copyright Clear- ance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923 USA, <www.copyriEht.com>. Prior to photocopying items for educational classroom use, please contact Copyright Clearance Center, Inc. This consent does not extend to copyright items for general distribution or for advertising or promotional purposes or to republishing items in whole or in part in any work in any format. Requests for special photocopying permission and reprint requests should be directed to Senior Director, Pub- lications,T he American Ceramic Society, 735 Ceramic Place, Westerville OH 43081 USA. Statements of fact and opinion are the responsibility of the authors alone and do not imply an opinion on the part of the officers, staff, or members of The American Ceramic Society. The American Ceramic Society assumes no responsibility for the statements and opinions advanced by the contributors to its publications or by the speakers at its programs. Registered names and trademarks, etc., used in this publication, even without specific indication thereof, are not to be considered unpro- tected by the law. Library of Congress Cataloging-in-Publication Data Pi telka,V ince. Clay : a studio handbook /Vince Pitelka. p. cm. Includes index. ISBN 1-57498-090-4 1. Pottery craft. 2. Pottery craft--Marketing. 3. Artists’ studios--Design and construction. I. Title. TT920 .P54 2001 738--dc21 2001022414 Contents Introduction and Acknowledgments ......... xiii Variations in Claybodies for Different .................. Applications and Firing Processes 8 .............................. .............................. 1 Clay and Claybodies 1 Analysis of Clay Properties 9 The Nature of Clay ....................................... 1 Water of Plasticity ............................................. 9 ........................... Mixing and Recycling Clay 10 Clay and Claybodies: Some Basic Questions Answered .................................... 2 The Low-Tech Approach ................................. 11 What Is Clay? ................................................... 2 Clay Mixers and Pug Mills .............................. 11 ............... What Makes Clay Behave the Way It Does? The Hopper Mixer or “Dough Mixer” 12 What Makes It Plastic? .................................... 2 The Soldner Mixer .......................................... 12 Why Do Different Clays Behave Differently? ...... 3 The Pugmill ................................................... 13 How Does Particle Size Affect Drying and Firing? ................................................... 3 2 Handbuilding ....................................1 4 What Are Flocculation and Deflocculation? ...... 3 Wedging the Clay ....................................... 15 Why is Aged Clay More Workable? ..................... 3 Cylinder Wedging .......................................... 15 What Are the Basic Structural Components Cone Wedging ................................................ 16 ......................................................... of Clay? 3 .............................. The Cut-and-SlapM ethod 18 What Happens When Clay Is Fired? What Are ..................... ........................... Wedging Large Amounts of Clay 18 Sintering and Vitrification? 4 .................................... Handbuilding: General Guidelines Classification of Clays 4 ....................................... and Suggestions 18 ........................... Primary and Secondary Clays 4 .................................... ................................................... Making Pinch Forms 20 Claybodies 5 ....................................... ................................. Coil Construction 23 Claybody Components 5 Making Round-Bottom Coil Pots with or ............................................. Accessory Fluxes 5 without a Puki ............................................. 24 ...................................................... Refractories 6 Coiling the Walls .......................................... 24 Tempering Materials or Fillers ........................... 6 Closing the Mouth of a Coil Form .................. 26 ...................................................... Plasticizers 6 Paddle-and-Anvil and Rib-and-Hand ......................................................... ....................................... Colorants 6 Forming Methods 28 ........................ ....................................... Common Types of Claybodies 6 Coil-Built Sculpture 29 vi CONTENTS ....................................... .............................. Slab Construction 29 Throwing off the Hump 57 Rolled Slabs and “Memory” ........................... 29 Throwing Bowls ............................................. 59 Combining Slab and Thrown Components ...... 29 Throwing Plates ............................................. 60 .......................................... Rolling Out Slabs 30 Throwing Pitchers. Vases. Jars. Bottles. Rolling Slabs by Hand .................................... 30 and Jugs ................................................... 62 Making Very Thin Slabs ................................. 30 Vessel Proportions .......................................... 62 Soft-Slab Construction .................................... 31 “Necking In” a Vessel .................................... 63 Soft-Slab Cylinders .......................................... 3 1 Throwing Pitchers and Vases ........................... 65 Soft-Slab Covered Boxes ................................. 31 Forming the Spout on a Pitcher ........................ 65 .............................. Slumped Slab Lids for Soft-Slab and Throwing Bottles and Jugs 66 .......................................... Stiff-Slab Vessels 32 Making Lidded Vessels .................................... 67 Slump-Molds ................................................ 32 “Grinding-In”Y our Lids ................................. 69 ............................................. Soft-Slab Masks 33 .......................................... Making Teapots 69 .......................................... Soft-Slab Sculpture 34 ................................................... Teapot Lids 70 .................................... Stiff-Slab Construction 35 ................................................ Teapot Spouts 70 ............................................. Stiff-Slab Boxes 35 ............................................. Teapot Handles 71 .......................................... Stiff-Slab Sculpture 37 ........................... Thrown-and-Altered Forms 72 ............ An Unconventional Approach to Slabs 38 Throwing Oval. Square. or Making Tiles ................................................ 38 Polygonal Forms .......................................... 72 ......... .......................................... Throwing Components to Be Assembled 73 3 Throwing 40 ................................................ Cutting Darts 73 Choice of Wheels and Seats ........................... 41 Lids for Thrown-and-Altered Vessels ............... 74 . ......... .................................... Throwing Right-Handed vs Left-Handed 42 Feet on Altered Forms 74 ............ ............... Wedging and Preparing Balls of Clay 42 Throwing and Using Closed Forms 74 Clay Consistency .......................................... 42 Paddling and Rib-Shaping Thrown Forms ......... 75 Correct Position for Centering ..................... 42 Throwing Large Pots-Coil Throwing and .................................... ...................................................... Multipiece Vessels 76 Centering 43 .................................... .......................................... Production Throwing 77 Wheel Wedging 45 .......................................... ................................. Drying Your Pots 77 Penetrating the Lump 46 ............... ......... Finishing the Bottoms of Your Pots 78 Measuring the Thickness of the Bottom 46 .................. Finishing without Trimming-the The Claw-Widening the Bottom 46 ................................................ Rolled Edge 78 Recentering ................................................ 49 Trimming Your Pots ....................................... 79 ............ ......... Compacting and Leveling the Bottom 49 Trimming Platters and Wide. Low Bowls 80 Lifting the Walls .......................................... 49 Trimming Bottle and Vase Forms ..................... 80 ............................................. ........................ The Gifin Grip 82 Lubrication While Throwing 50 .................................... ................................. To Sign or Not to Sign 82 Compressing the Rim 50 ..................... Making and Applying Handles 82 Trimming Excess Clay or Irregularity from ................................................... the Rim 50 4 Plaster Working. Mold Making. and .................. Skill Development with Cylinders 51 ....................................... Slip Casting 88 ............... What To Do with the Basic Cylinder 51 ....................................... Plaster in Drainpipes: A Plumbing Nightmare- Remove All Water 51 ....................................... How to Clean Up 89 Trim Excess Clay from the Base ..................... 52 ......... Measuring. Mixing. and Pouring Plaster 89 Removing the Pot from the Wheel ............... 53 Water to Plaster Tables .................................... 90 Throwing on Bats ....................................... 54 The Use of Cottles ....................................... 91 .................................... Throwing on Canvas 54 Using Strips of Sheet Metal or Linoleum for Critical Points in Throwing ........................... 55 Mold Forms ............................................. 91 vii CONTENTS .................................... ........................... The Concept of Draft 91 Yield from Different Clays 111 Mold-Release Agents (Parting Agents) ............ 91 Application and Desired Specific Gravity ......... 112 ................................. .......................................... Polishing Terra Sigillata 112 Drying of Molds 91 ....................................... ............ Firing Temperatures 112 Making and Using Plaster Press Molds 92 ................................. Coloring Terra Sigillatas 112 ........................... Making Slip-Casting Molds 92 ........................... ........................ Colored Clay Techniques 113 Open-Pour Slip-Casting Molds 93 ................................................... Basalt Body 114 ........................ Multipiece Slip-Casting Molds 93 ............................................. Clay Marquetry 114 Multipiece Flick/Smear Molds from Plastic ................................................ .......................................... Clay Murrini 114 Clay Prototypes 93 ........................ Lamination of Colored Clays 116 Multipiece Molds from Rigid (Not Plastic Clay) Prototypes .......................................... 94 Layered Colored Clays ................................. 116 Mixing and Pouring Casting Slip .................. 96 Marbleized and Grained Colored Clays ......... 117 ..................... Pouring Your Molds ....................................... 96 Rocklike Effects in Colored Clay 117 ......................................................... Neriage 117 ...... ...................................................... 5 Surface Decoration on Greenware 98 Nerikomi 118 ................................................ .................. Pate-sur-Pate 118 Decorative Effects during Forming 98 ..................... Slip Effects with Colored Clays 118 ................................. Impressed Decoration 99 ................................. Sprigged Colored Clay 118 ................................. Subtractive Methods 100 ................................................... Swirlware 118 ....................................... Additive Methods 101 Burnishing and Polishing ........................... 102 6 Glazes and Glazing ........................... 120 ........................... .............................. Slips and Slip Decoration 102 Introduction to Glazing 120 How to Select a Slip Formula ........................ 102 Glaze Color ................................................... 121 ..................... ..................... Flocculation and Deflocculation 103 Glaze Transparency and Surface 121 ............ ........................... Mixing a Slip without a Deflocculant 104 Approaching Glaze Design 121 ..................... Mixing a Slip with a Flocculant 104 .................................... Glaze-Firing Ranges 122 ............... Adding a Flocculant to a Liquid Slip 104 ............ Referring to Glazes by the Firing Cone 122 .................. Mixing a Slip with a Deflocculant 104 ................................................ Very Low.Fire 122 ............ Desired Consistency of a Slip Mixture 104 ...................................................... Low-Fire 122 ..................... Adding Colorants to White Slip 105 ............................................. Low-Mid-Range 122 ........................ Slip-Decorating Techniques 106 ................................................... Mid-Range 123 .............................. Polychrome Slip Painting 106 ...................................................... High-Fire 123 ...................................................... Sgraffito 106 .......................................... Multirange Firing 123 ................................................ Slip Trailing 106 .......................................... Glaze Variations. by Design and Feather Combing 107 ............................................. by Accident 123 ................................................ Slip Marbling 107 ................................. The Choice of Whether to Buy or Mishima (Slip Inlaying) 108 ............................................. Mix Glazes 123 ................................................ Slip Layering 108 .................................... Organizing Glaze Recipes: Card Files Slip-Resist Techniques 108 .......................................... and Software 124 ............................................. Slip Texturing 108 ............................................. Converting Glaze Recipes to Slip Stamping 108 ................................. Standardized Form 124 ........................ Pate-sur-Pate (Paste-on-Paste) 108 .......................................... ..................... Mixing Glazes 124 The Wonders of Terra Sigillata 109 ..................... Using a Triple-Beam Gram Scale 125 Making Terra Sigillata: Batch Mixing. Deflocculants. and Specific Gravity ............ 109 Glazing Methods ....................................... 127 ............................................. .............................. Initial Settling 110 Using Resist Compounds 127 .............................. .................. Decanting the Suspension 110 Using Resists for Glaze Decoration 128 ........................ .............................. Concentrating the Suspension 111 Contamination of Glazes 129 dii CONTENTS ............... Glaze Consistency and Thickness Testing Glaze Materials and Glazes 157 of Application. ............................................ 129 Making Test Tiles .......................................... 158 Glaze Effects Resulting from Thickness Testing Glaze Hardness ................................. 158 ............................................. of Application 130 .................. Testing Durability of Fired Wares 158 .................................... Using Multiple Glazes 131 Ceramic Calculation Software. Unity Formulas. Using Oxide Washes and Patinas .................. 131 and Limit Formulas ................................. 158 ....................................... Glaze Application 132 How Do We Use Ceramic Calculation and the Brushing and Sponging Glazes ..................... 132 Unity Formula? .......................................... 159 ............................................. Dipping Glazes 133 .............................. Pouring Glazes ............................................. 134 7 Kilns and Firing 160 Spraying Glazes ............................................. 134 Types of Firings .......................................... 161 Avoiding Problems during Glazing, and Dealing Types of Kilns ............................................. 161 ..................... with Them When They Occur 135 ................................................ Electric Kilns 162 Multiple Firings. and Reglazing ................................................... ....................................... Fuel Kilns 162 Glaze-Fired Wares 136 ................................................... ............... Wood Kilns 163 Checklist of Guidelines for Glazing 136 .................. ........................ General Kiln and Firing Practices 163 Commercial Glaze Products 137 ................................................... ................................................ Firing Logs 163 Underglazes 137 ................................................... ......................................................... Ventilation 163 Stains 137 .................................... ........................ Don’t Bum Yourself! 163 Low-Fire Commercial Glazes 138 ....................................... Opening Hot Kilns 164 Mid-Range and High-Fire ........................... Commercial Glazes .................................... 138 Care of Refractory Surfaces 164 Lusters ......................................................... 138 Preparing and Loading Kilns ........................ 164 .................. .............................. China Paints (Overglaze Enamels) 139 Electric Kiln Preparations 164 ........................... Gas Kiln Preparations .................................... 164 Glazes: The Technical Side 139 ........................... ........................... Kiln Shelves and Furniture 164 What Are Glass and Glaze? 140 Oxides. Oxidation. and Reduction .................. 140 Cleaning Shelves and Applying ................................................ Shelf Wash 165 ................................................ Reoxidation 141 .............................. Temperature Measurement: Pyrometers and Components of a Glaze 141 J?yrometric Cones ....................................... 166 ......... The Glass Formers: Acidic Oxideeilica 141 ........................... Making Proper Cone Packs 168 Refractories: Stabilizers-The Neutral Oxides- ............................................. ................................................... Loading Kilns 168 Alumina 142 ............... Selecting and Placing Kiln Furniture 168 Fluxes: Basic Oxides-Coefficiento f Expansion-Eutectics ................................. 142 Loading a Bisque-Firing ................................. 169 ................................. ............................................. Loading a Glaze-Firing 170 Glaze Modifiers 146 ........................... Miscellaneous Components 146 Determining Appropriate Firing and ....................................... Cooling Ramps 171 Primary Chemical Variations in Glazes for Different Firing Ranges. ............................. 146 Bisque-Firing Ramps .................................... 171 Adjusting the Qualities of a Glaze ............... 147 Glaze-Firing Ramps ....................................... 172 ............................................. ............................................. Cooling Ramps 173 Glaze Color 148 Coloring Oxides .......................................... 149 Firing Theory and Practice ........................... 173 Common Traditional Glazes ........................ 150 Firing Clay: Chemical and ....................................... Physical Changes 173 ................................. Salt and Soda Glazing 151 ..................... The Sources and Effects of Heat 174 ... The Chemistry and Physics of Glaze Firing 152 Heat Units-Calories and BTUs ..................... 175 ......... Reactions and Properties during Heating 152 .............................. The Combustion of Fuels 175 ...... Reactions and Properties in the Fluid State 152 Convection Currents and Back Pressure in ................................................... Reactions and Properties as the Glaze Starts Fuel Kilns 176 ...................................................... to Cool 152 Oxidizing. Neutral. and Reducing Atmospheres Glaze Faults ............................................. 154 in Fuel-Burning Kilns ................................. 176 CONTENTS ix Different Fuels and Surface Exposure ............ 177 Temperature Control and Shutoff Devices on ............................................. ............ Electric Kilns 199 The Firebox-The Heart of a Fuel Kiln 178 ........................ Electric Kiln Venting Systems 201 Flames and Flame Path in the Combustion Zone ....................................... 178 Kiln-Wall Thickness/Construction and .................................... ........................... Temperature Rating 201 Primary and Secondary Air 179 ............... Size and Design of Top-Loader Kilns 201 .......................................... Firing Fuel Kilns 179 .............................. Element Support Systems 201 ............ Controlling Temperature in Fuel Kilns 179 Installation Requirements for Top-Loader Controlling and Correcting Temperature and Electric Kilns ............................................. 201 .................. Atmosphere in an Updraft Kiln 180 ............... Heavy-Duty Industrial Electric Kilns 202 Controlling and Correcting Temperature and ..................... .................. Purchasing a Used Electric Kiln 202 Atmosphere in a Downdraft Kiln 181 ...... ........................... Maintenance and Repair of Electric Kilns 203 Watching the Flame Shape 182 .............................. ........................ Problems with Corrosion 203 Specialized Firing Processes 182 ........................ Dawson Kiln Sitter Problems 203 ................................................... Raku Firing 182 ..................... Electrical Problems and Repairs 204 ....................................... Salt and Soda Firing 184 ........................ Electrical Terminals and Wires 204 ................................................ Single-Firing 186 .................................... Switch Replacement 205 ........................ Wood Kilns and Wood Firing 187 Power Supply Problems ................................. 205 The Coal Bed ................................................ 187 Element Replacement .................................... 205 Air Ports ...................................................... 188 Rehactory Repairs on Electric Kilns ............... 207 Types of Wood Fireboxes and ............................................. Fuel Kiln Selection. Design. Construction. Grate Systems 188 ............................................. and Repair 207 ....................................... Watching the Ports 190 ..................... Choosing the Right Kiln Design 208 .......................................... Small Wood Kilns 190 .......................................... Kiln Proportions 208 Promoting Flashing and Residual .................. .......................................... Proportions for Downdraft Kilns 208 Ash Deposition 191 ...................................................... ..................... Kiln Size 209 Choice of Wood Types and Sizes 191 ........................ Commercially Made Gas Kilns 209 Regulating Oxidation and Reduction .................................... ................................................ Gas Kiln Installation 209 with Wood 192 ....................................... ............................................. Venting Fuel Kilns 210 Sagger Firing 192 .................................... Venting Updraft Kilns 210 ....................................... Sawdust Smoking 193 .............................. Venting Downdraft Kilns 211 Bonfire Firing ............................................. 194 Burner Systems .......................................... 211 How To Do a Bonfire Firing ........................... 195 Gas Burner Systems ....................................... 211 Selecting the Clay and Preparing Gas Burner Ignition and Safety Systems ......... 211 ................................................... the Wares 195 ......... Programmable Controllers on Gas Kilns 213 Selecting and Preparing the Fuel ................................................ Gas-Line Pressure: Variations and Manure 195 ....................................... and Measurement 213 ............ Preparing the Pit for Blackware Firing 195 ..................... Gas Burners and Entrained Air 214 ......... Firing the Wares Directly in the Bonfire 196 ............... Atmospheric/Natural Draft Burners 215 ...................................................... Pit Firing 196 .................................... Simple Tube Burners 215 Bonfiring with a Grate, Cage, or Drum ............ 196 Flame-Retention Problems ........................... 216 .................. Stacking and Covering the Wares 196 Gas-Air Mixing and Turbulence: Flame- .................................... ................................. Kindling the Bonfire 197 Retention Burner Tips 216 ................................. ............................................. The Oxidizing Bonfire 197 Venturi Burners 217 ................................. ................................................ The Blackware Bonfire 197 Pilot Burners 218 ....................................... ............................................. Cleaning the Wares 197 Power Burners 218 ....................................... .................................... Postfiring Polishing 197 Oil-Burner Systems 219 ...... .................................... Electric Kiln Selection, Design, and Repair 197 Drip-Feed Oil Burners 219 Electric Heating Elements .............................. 198 Atomizer Oil Burners .................................... 219 Reduction-Firing in an Electric Kiln ............... 198 Safety Systems with Oil Burners ..................... 220
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