Archaeological Conservation Using Polymers: Practical Applications for Organic Artifact Stabilization (Texas A&M University Anthropology Series) PDF
Preview Archaeological Conservation Using Polymers: Practical Applications for Organic Artifact Stabilization (Texas A&M University Anthropology Series)
Archaeological Conservation Using Polymers i Texas A&M University Anthropology Series D. Gentry Steele, General Editor Series Advisory Board William Irons Conrad Kottak James F. O’Connell Harry J. Shafer Erik Trinkaus Michael R. Waters Patty Jo Watson ii iii Archaeological Conservation Using Polymers Practical Applications for Organic Artifact Stabilization . Foreword by J. M. Klosowski • Copyright © by C. Wayne Smith Manufactured in the United States of America All rights reserved First edition The paper used in this book meets the minimum requirements of the American National Standard for Permanence of Paper for Printed Library Materials, .-. Binding materials have been chosen for durability. Library of Congress Cataloging-in-Publication Data Smith, C. Wayne. Archaeological conservation using polymers : prac- tical applicatons for organic artifact stabilization / C. Wayne Smith.—st ed. p. cm.—(Texas A&M University anthropology series ; no. ) Includes index. --- (alk. paper)— --- (pbk. : alk. paper) . Antiquities—Collecton and preservation. . Archaeology—Methodology. . Archaeological chemistry. . Polymers. I. Title. II. Series. . .'—dc The author and publisher gratefully acknowledge a generous grant from Bill Caruth in support of publication of this volume. v To Helen, Thanks for sharing this and all my adventures. vi Contents Foreword by J. M. Klosowski, ix Acknowledgments, xm Introduction, 3 CHAPTER 1 Laboratory Setup, 7 Major Instrumentation, 7 Small Necessities in the Laboratory, 8 Chemicals, 9 2 Baseline Mechanisms, 13 Dowel Experiment, 13 Mass Spectrographic Analysis of Out-Gases Created from the Dehydration of Archaeological Wood Samples, 17 3 Archaeological Wood, 21 The Challenge of Conserving Waterlogged Wood, 21 Degradation and Shrinkage, 22 Waterlogged Wood from Saltwater Environments, 22 Case Study: Waterlogged Wooden Buttons with and without Associated Thread, 26 Dry-Site Artifacts—Dry and Desiccated Wood, 28 Reprocessing and Stabilization of PEG-Treated Wood, 30 Tongue Depressor Experiment, 31 Case Study: Re-treatment of Two PEG-Treated Sabots, 40 Re-treatment of PEG-Treated Waterlogged Wood, 43 Case Study: Treatment of Waterlogged Wood Using Hydrolyzable, Multifunctional Alkoxysilane Polymers, 45 4 Leather Preservation, 60 Archaeological Leather, 60 Cleaning, 62 Chemical Cleaning, 62 Treatment of Leather, 62 PEG/Air-Drying Treatments, 63 Freeze-Drying PEG-Treated Artifacts, 64 PEG and Other Polymers, 65 Passivation Polymer Processes, 66 Case Study: A Successful Treatment Strategy for a Waterlogged Shoe, 66 Passivation Polymer Treatment for Dessicated Leather, 69 An Effective Treatment for Dry Leather, 70 Suggestions for Treating Leather between Sheets of Glass, 72 Storage and Display of Leather Artifacts, 72 5 Composite Artifacts, 74 Case Study: Preservation of a Composite Artifact Containing Basketry viii and Iron Shot, 74 6 Cordage and Textiles, 81 CONTENTS New Techniques for the Preservation of Waterlogged Rope, 81 Silicone Treatment Strategies, 82 Frankfurter Method of Rope Preservation, 82 Treating Waterlogged Rope in a Nonpolar Suspension Medium, 82 Incorporating the Use of Nonpolar Suspension Mediums and Elements of the Frankfurter Method into “Traditional” Silicone Treatment Strategies, 83 Case Study: La Belle Rope, 83 Case Study: Preservation of Waterlogged Canvas from Port Royal, 90 7 Glass Conservation, 93 Devitrification, 96 Removal of Sulfide Stains from Lead Crystal, 96 Consolidating Waterlogged Glass Using Passivation Polymers, 96 An Effective Silicone Oil Treatment Strategy, 96 Reconstruction, 98 Case Study: Preservation of Seventeenth-Century Glass Using Polymers, 100 Case Study: Preserving Waterlogged Glass and Cork, 108 8 Ivory and Bone, 112 Basic Structural Differences, 112 Equipment Setup for Very Fragile Bone and Ivory, 113 Case Study: Consolidating Friable Bone, 114 Case Study: Ivory from Tantura-B Excavations in Israel, 115 Case Study: Waterlogged Tusks from Western Australia, 116 9 Expanding the Conservation Tool Kit, 119 Computerized Tomography and the Stereolithographic Process, 120 Case Study: Scanning an Encrusted Artifact—CT Scanning Used as a Diagnostic Tool, 121 New Tools—New Directions in Research, 121 Notes, 125 Index, 127 Foreword ix Preservation with reactive chemicals can be mers and cross-linkers to penetrate cell walls called by many names but the most promi- and then adding catalyst. Each technique has nent is von Hagen’s term, plastination. Other its advantages. terms are chemical bulking and reactive fill- Both techniques often require specimen ing. They are all used to describe the process preparation, or preservation, which might of coating and impregnating cells with ma- require rinsing them clean and setting the terials that react with the walls to prevent tissues with formalin solution. Next is the water from attaching and reacting. In many medium exchange, where water in cells and cases, we are also talking about filling the cell cavities is exchanged for a more compatible or opening to prevent collapse. and less reactive medium, usually acetone, The goal is to place a substance on the but sometimes alcohols. The exchange is con- cell that reacts to the carbonols (—COH) tinued until most of the water is eliminated. present on much of the cell surface. Reac- The next step is penetration with reactive tive silanes (cross-linkers) are particularly materials. The classic von Hagen procedure adept at this and can be combined with poly- uses a mixture of a catalyst (typically dibutyl- mers (carbonol or silanol [—SiOH] ended tindilaurate) and a silanol-ended polymer. polymers) that also react with the silane This technique involves immersing the ac- cross-linkers. Thus we have silane cross-link- etone-saturated specimen in a bath of this ers that react to the cell wall, to each other, mixture under a very slight vacuum and boil- and to the polymer. Almost always, this re- ing off the acetone with the vacuum to leave quires one or more catalysts to hasten and little voids that are then filled with polymer/ complete the reactions. catalyst mixture. When the acetone is gone, We can use very reactive cross-linkers like the cavities are drained of excess solution and methyltriacetoxysilane MeSi(OCOCH) or a cross- linker, typically tetraethoxysilane 3 3 less reactive cross-linkers like methyl- Si(OEt), is added. As this penetrates the cavi- 4 trimethoxysilane MeSi(OCH). Typically, ties, the polymer, cross-linker, and catalyst 3 3 when deep penetration into cell walls or body converge and react. The reaction is permit- cavities is desired, slower-to-react materials ted to continue until it is complete (typically are used to postpone the reaction until pen- in some heated chamber since often the etration is fairly complete. Alkoxy functional cross-linker is put into the system from a (alcohol releasing) cross-linkers are pre- vapor). ferred, as their reaction to the cell wall or to Our technique uses formalin (if desired) the polymer usually requires a catalyst. The and acetone to displace water. A mixture of von Hagen procedure uses a polymer and a polymer and cross-linker is then added to catalyst to impregnate and coat the cells fol- accomplish cell penetration. The polymer lowed by the introduction of the cross- and cross-linker mixture is preferable be- linker. Our technique involves using poly- cause it is more stable than the polymer and
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