The Art of Flotation:

Archaeobotany in the field


A photo gallery of flotation from Dorian Fuller and friends

Flotation is the art behind the science of archaeobotany. Take dirt (preferably archaeological), water, a container and a sieve, and mix: flotation. But there are many variants depending on setting, soils, equipment and energy. On these pages is the start of a collection of flotation from various projects.

flotation samples drying, Sanganakallu, South India (Photo: Eleni Asouti)

A Short History of Flotation

Flotation was first carried out in America at the Apple Creek site in the Lower Illinois River Valley (as part of Stuart Streuver's 'Lowillva' project) in 1962, and it was used on other sites in the project such as the Macoupin site in 1968. Although discussion of the technique was not published until 1968.

  • Streuver, S. 1968. Flotation techniques for the recovery of small-scale archaeological remains. American Antiquity 33: 353-362

Subsequently it was conducted on large scale at the famous Koster site in Illinois, which was first tested in 1969 and excavated extensively from summer 1970.  The main method used by this project simple flotation in a river: in this method a sample is immersed in water within a metal drum with a coarse sieve base, heavy material is caught in this lower sieve while floating material is scooped off the surface of the water with a fine sieve (like a tea-strainer).

Flotation being carried out ca. 1970 as part of the Koster Project. Photo scanned from S. Streuver and E. Houlton (1979) Koster: Americans in Search of Their Prehistoric Past. [available in reprint edition]

Shortly after the first Lowillva aaplication flotation was carried out by an American team working in Iran on the Deh Luran Plain (1963), but the method was modified by using a wash-over method of bucket flotation which provided the basis for the important archaeobotanical analysis by Helbaek:

  • Helbaek, H. 1969. Plant collecting, dry-farming, and irrigation agriculture in prehistoric Deh Luran. In F. Hole, K. FLannery, & J. Neely (eds.) Prehistory and human ecology of the Deh Luran Plain,  Memoirs of the Museum of Anthropology, University of Michigan, 1: 383-426. 

The success of bucket flotation was highlighted by the contrast between archaeology before and after flotation, as noted by Hole et al.: "The reader will note that our preliminary report on the 1961 season states confidently that "plant remains were scarce at Ali Kosh." Nothing could be farther from the truth. The mound is filled with seeds from top to bottom; all that was "scarce" in 1961 was our ability to find them, and when we added the "flotation" technique in 1963 we recovered a stratified series of samples totalling 40,000 seeds." --Hole, Flannery and Neely 1969 Prehistory and Human Ecology of the Deh Luran Plain  p. 24

The Streuver bucket method could be readily adapted to be carried out on a small scale, on small samples, in individual buckets, as was practiced in the AMerican Southwest in the 1970s, e.g. at the Salmon Ruin.

  • Bohrer, V. L. & K. R. Adams (1977) Ethnobotanical Techniques & Apporaches at Salmon Ruin, New Mexico. Eastern New Mexico University Contributions in Anthropology 8(1).

Applications elsewhere in the Mediterranean and Europe were actively promoted by the Palaeoeconomy research group of Eric Higgs, who porbably developed the first true flotation machines of "froth" flotation or the "Siraf" type,  as shown above  at Saqqara, Egypt. For early examples, see, e.g.

  • Jarman, H. N., A. J. Legge, J. A. Charles 1972. Retrievals of plant remains from archaeological sites. In: E. S. Higgs (ed.) Problems in Economic Prehistory. Cambridge University Press, pp. 39-48
  • French, D. (1971) An experiment in water-sieving. Anatolian Studies 21: 59-64

  • Williams, D. (1973) Flotation at Siraf. Antiquity 47: 288-292

  • Stewart, R. B. and W. Robertson, IV (1973) Application of flotation technique in arid areas. Economic Botany 27: 114-116

These Old World flotation machines inspired the development of flotation machine design as part of the Shell Mound Archaeological Project  in the American mid-west, and the so-called SMAP-type machine has become a standard baseline from which many flotation machine designs have been developed, e.g. in China

  • Watson, P. J. 1976. In pursuit of prehistoric subsistence: a comparative account of some contemporary flotation techniques. Mid-Continental Journal of Archaeology 1(1): 77-100

The first application of flotation in Southeast Asia was carried out in 1973 by Ian Glover,

  • Glover, I. 1979. Prehistoric plant remains from Southeast Asia, with special reference to rice. In. M Taddei (ed.) South Asian Archaeology 1977. Naples: Instituto Universitario Orientale. Pp. 7-37

Its application in India began in the later 1970s at Deccan College excavations at Inamgaon:

  • Kajale, M. D. 1977. Plant economy at Inamgaon. Man and Environment 1: 64-66

Flotation using a SMAP-type machine, was introduced in East Asia, in Japan, in the 1970s through research by Gary Crawford, see, e.g.

  •  Crawford, G. W., William Hurley and Masakazu Yoshizaki   1976       Implications of Plant Remains from the Early Jomon Hamanasuno Site, Hokkaido.  Asian Perspectives XIX(1): 145-155
  • Crawford, Gary W.   1983  Paleoethnobotany of the Kameda Peninsula Jomon. Anthropological Papers No. 73. Museum of Anthropology, University of Michigan, Ann Arbor

from here a modified SMAP-type machine was then introduced to China on early American-Chinese archaeological collaborations in the late 1980s and early 1990s.  Systemaic flotation has become widely promoted even more recently in China, especialy in the 1990s through the research of Dr. Zhao Zhijun of the Chinese Academy of Social Sciences.  In addition, and in parallel, Prof. Watanabe began flotation around Kyoto as early as 1971. The Chinese archaeologist Xiong Haitang, who observed the technique while visiting Nagoya University, was inspired to publish an account of the method in Chinese in the journal Nongye Kaogu in 1989. This method was then applied be the Chinese Academy of Social Sciences excavations at Lilou, Henan in 1992. Nevertheless, it is more recent and sustained efforts of Dr. Zhao that have spread archaeobotanical research more widely in China. 

For a comprehensive account of many varied flotation methods, one can consult the book of Deborah Pearsall Paleoethnobotany (first edition 1989; second edition 2000).  Further bibliography on archaeobotanical flotation is also available from about.com.