An Application of Casting Techniques For Observing and Recording of Microwear

Maney Publishing

An Application of Casting Techniques For Observing and Recording of MicrowearAuthor(s): Hugues PlissonSource: Lithic Technology, Vol. 12, No. 1 (April 1983), pp. 17-21Published by: Maney PublishingStable URL: http://www.jstor.org/stable/41999763 .

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17

Research Report

An Application of Casting Techniques For Observing and

Recording of Microwear

Hugues Plisson Centre de Recherches Préhistoriques de Paris I U.E.R. d'Art et Archéologie, 3 rue Michelet, 75006 Paris, France

The functional analysis of stone tools according to Keeley's (1980) newly-developed method has awakened lively interest in Europe. Using an optical microscope one can observe microwear traces specific to the utilization of experimental and archaeological flint tools on wood, bone, hide, meat, etc. The numerous implications of this research have led many laboratories to include it in their research programs.

The application of the Keeley method to the analysis of tools from various areas and time periods has encountered certain problems. Some pieces are too large to fit between the microscope stage and the objectives; patinated or lightly- colored areas of the tool surface can be difficult to observe due to lack of contrast; and tools belonging to private collections or museums sometimes cannot be transported to the observer's laboratory for study. These problems have been dealt with in the past by selecting a few specimens for study from among the available tools.

In our experiments we have developed a simple and, hopefully, better solution to these problems. We have been casting of the tool surfaces with special products used in metallographic microscopy.

Although ordinary rubbers and mastics do not reproduce minute details with sufficient accuracy for microwear analysis, we have found that "metallographic type" varnishes and acetate peels produce casts of micro-use suitable for study at high magnification. The cast must exhibit a high fidelity in order to identify certain subtle but crucial features for tool use diagnosis; such traces are not reproduced by poor replicas. It is essential that differences between traces on tools produced by

natural forces and those due to man's utilization not be distorted by the texture of the casting material, otherwise the rubber itself is seen rather than the print of the actual lithic material.

Two products well known for their simple and effi- cient use were tested: the "Replie Varnish" and the "Rhodialine"*. Other products which are similar but sometimes more sophisticated and expensive, may also be used according to preference or local availability.

The analysis consisted of using a reflected light optical microscope (Nikon Labophot equipped with 5, 10, 20 & 40 power Plan Achromat objectives, and CFW 10 X oculars) to compare originals with casts of a wide range of experimental and archaeological flint flake and blade tools (used on bone, wood, hide, meat, etc.), and of obsidian, quartzite and basalt surfaces. Only insignificant differences were found to occur between the real artifacts and the copies. In fact the cast also offers an advantage over the original in that it eliminates problems such as glare on the original tool surface which can make the analysis difficult. Even at 400X magnification which reveals the actual grain structure of some rock types, the internal texture of the varnish and of the acetate peel is not discernible. However this is not true of casts made from latex (Beyries 1981) or silicon rubber (Ilkjaer 1979) such as R.T.V. 1502, which show a pitted or greasy surface at high magnification (Figures 4 and 5).

It is possible to distinguish between usewear traces and natural alterations on casts made with Replie Varnish and Rhodialine. These casts can be accurately analysed in place of the actual tools, although obviously even the most perfect replica can not be as reliable as the original itself.

Replie Varnish and Rhodialine fire of comparable quality for the magnification ranges employed in optical microscopy. Ordinary observation as well as blind tests show that various kinds of microwear traces can be recognized on casts made with either product. However Replie Varnish seems to simplify the micro-structure very slightly, accentuating the contrast between the micro-polish and the flint surface. Rhodialine, a product of more recent concep- tion, is used in industry for ultra high power magnification, and would probably be preferable for scanning electron microscope applications (greater than 500X).

Replie Varnish is simple to use. It comes in liquid form and is brushed directly onto the surface (previously cleaned with acetone) of the object to be cast. Prior application of a gummed label at the margin of the portion of the artifact to be duplicated facilitates removal of the replica. Three



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coats are applied in order to create a rigid cast of flat edges, and four or more coats ensure a stiff replica of areas with pronounced reliefs (retouch, granulation, etc.) Drying time between coatings is two or three hours. The cast is removed by sliding a razor blade under the gummed label, trying to avoid scratching the original tool surface. Special care must be taken not to tear the replica while removing the cast from sharp-ended tools such as borers and burins.

Rhodialine is more rapid to use. It comes in the form of a plastic sheet measuring 1250 by 850 mm. We tested the various available thicknesses (75 to 30/100 mm.) and found that 12/100 mm. was a good compromise between rigidity and drying speed; however 75 and 90 suit better for the coarse- grained surfaces (e.g., basalt and quartzite). Larger thicknesses provide poor replicas and are in fact sold as interpolated sheets.

A tongue shaped piece of the desired size is cut from the sheet, and one extremity is then diluted for a few seconds in pure acetone and applied to the tool surface which has also been moistened with acetone. After 15 or 20 minutes the cast is removed by simp- ly ungluing it, beginning at its free edge. The dif- ficulty lies in estimating how much to soften the cast initially: if it is too hard, the Rhodialine adheres badly and if it is softened too much, it tends to melt.

The replicas require protection from chemical at- tack and mechanical damage and will last for a year or more if stored away from heat. We successfully store our samples in small plastic bags.

As the translucency of the casting materials may interfere with good incident-light reflection, we recommend darkening the underside of the replica with an ordinary felt-tipped marker. The casts then are ready for study according to the Keeley (1980) method. Our replicas are negatives of the original relief, but due to the low depth of field of the optical microscope and because of its paradoxical image, the observer does not in fact have the impression of viewing a reversed image of the artifact surface. The inversion is automatically corrected by the human eye (Figures 2,3,4,5,7,8).

Defects in the replicas which may occur during preparation or handling can be easily recognized by the observer.

Care should be taken not to scratch the artifact with the razor blade while removing the Replie Var- nish; otherwise the procedures are apparently harmless to artifacts and can be repeated as many times as necessary. Both Replie Varnish and Rhodialine are soluble in acetone.

The two products have been satisfactory for use with many lithic artifacts, and more particularly for experimental work where it was necessary to keep

very precise records of modification of the tool surface (Plisson and Mauger, in press).

Although it requires more skill to use, Rhodialine appeared to be more practical than Replie Varnish as it rapidly produces replicas and is much easier to remove. However, Rhodialine casts are more fragile and sometimes more tiring to observe because of dif- ficulty in orientation at the correct angle for observation under incident light due to the raised impression of the boundary of the edge. For this reason we prefer to use Replie Varnish for the slightly rounded edges (e.g., end scrapers). The choice of products will depend upon the needs of each researcher.

In any case, Replie Varnish and Rhodialine are highly superior to latex or silicone rubber casts which tend to flatten and in general distort the characteristic features of the microwear traces (Figures 1-5). The advantages of such metallographic type

casting products are numerous. They allow analysis of voluminous and light-colored objects, provide access to artifacts which cannot otherwise be removed for study and furnish a complement to micrographs for recording microwear traces. They are particularly effective for duplicating traces on experimental tools at various stages of utilization or treatment, for recording significant microwear patterns and as a means of transmitting information among microwear analysts. One other way in which they can be useful is to clean the tool surface of ex- traneous material or to remove these materials for analysises; for this reason we caution their use on friable surfaces (e.g., bone, ceramics).

In summary, Replie Varnish and Rhodialine were shown to be good casting materials for observing and recording of microwear traces because they are easy to use and they consistently produce replicas which are accurate enough to be studied at high magnifications.

♦Replie Varnish is a product of PRESI Firm, 2 Av. Hector Berlioz, Poisat, 38320 EYBENS, France. Rhodialine is a product of COFRAMAP, 10 Av. des Coquelicots Z.A. des Petits Carreaux, 94385 BONNEUIL Cedex, France.

Acknowledgments

I would like to thank Patricia Anderson, Gérard Firmin, and Emily Moss for their helpful comments and assistance.



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References Cited

Beyries, S. 1981 Etude des traces d'utilisation sur des em-

prientes en latex. Bulletin de la Société Préhistorique Française 78:198-199.

Ilkjaer, J. 1979 A new method for observation and record-

ing of use-wear. In Lithic use-wear analysis , ed. by B. Hayden: 345-349. Academic Press, New York.

Keeley, L. H. 1980 Experimental determination of stone tool

uses . A micro-wear analysis . University of Chicago Press, Chicago.

Plisson, H. and M. Mauger in Chemical and mechanical alteration of press microwear polishes: an experimental ap-

proach. In The Proceedings of the Fourth International Flint Symposium of Brighton Polytechnic (10-15 April 1983).

Current News

International List of Microwear Analysts

At the recent International Symposium in Brighton, an informal meeting of microwear analysts was held. At that time, it was decided to compile a list of all people doing wear analysis and their work. Dr. Patrick Vaughan and Linda Owen are compiling this international list. It will include names, addresses and the kinds of research being done. Anyone who would like to be included in the list, which will be available to all entrants, should contact:

Linda Owen List of Wear Analysts Institut für Urgeschichte Schloß Universität Tübingen 7400 Tubingen Federal Republic of Germany

Recent Publications

Adkins, L. and R. A. Adkins

1982 A thesaurus of British archaeology. Barnes and Noble Books, Totowa, NY. 319 pp, numerous illustrations, index. $27.50.

The book is divided into 11 segments, most arranged chronologically -- Paleolithic through Medieval periods - but with two final chapters on "archaeological techniques" and "miscellaneous". The latter con- tains, on pp. 257-264, a useful review on "flint and stone working" (types of frac- tures, methods of flaking, chipping floors, and the manufacture of ground stone tools). These are brief but useful statements and have bibliographic guides for further reference. In the earlier chapters, organized by chronological period, the lithics of each period are described and illustrated. For example, under "Neolithic", there are good sum- maries of flint mining, stone axe factories, stone axe trade, methods of axe hafting, etc. These entries make the book of interest to lithic technologists working out- side Great Britain. [TRH]

Barber, J., ed.

1981 Quartz technology in prehistoric New England, 141 pp, illustrations. $5.00 (order from R. J. Barber, Institute for Conserva- tion Archaeology, Peabody Museum, Har- vard University, Cambridge, MA 02138).

This is the first attempt that ar- chaeologists in the Northeast have made towards the explanation and understan- ding of quartz lithic technology, and the Archaic period quartz industries which are common in this area. The volume is made up of papers from 10 contributors, cover- ing a fairly wide range of interests, related to the prehistoric quartz industries in the Northeast. Although copyright in 1981, it has only very recently come out. [F.M. Carty]



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An Application of Casting Techniques For Observing and Recording of Microwear