Table Of ContentArchaeological 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
