Canadian Historic Sites: Occasional Papers in Archaeology and History No. 1

A Classification System for Glass Beads for the Use of Field Archaeologists,

by Kenneth E. and Martha Ann Kidd

The Technology of Glass Beads

This paper is part of a much more comprehensive investigation on the study of glass beads used for trade with the Indians of northeastern North America. Basic to such a study is the need for a satisfactory terminology and the authors, not finding one ready at hand, decided to try to work one out. After accomplishing this to their satisfaction, they decided not to await the publication of the larger work, but to make the results available to any who might wish to use it. It should be stressed, however, that our firsthand knowledge has been confined largely to specimens from the Northeast, and while the classification scheme should be of worldwide application, our specific knowledge does not extend to all of North America, and there may be many types which we have not seen.

There have always been, of course, terms by which the different kinds of beads have been known and identified. Some of them have referred, however vaguely, to physical characteristics; in this category we would place such terms as "pound," "seed" and "tube." Others, derived from sources now often obscure, are "macca," "cornaline" and "rosetta." None of these has any precise significance, and although they may be useful in the trade, are of no assistance to the archaeologist. The use of such terms as "pony" and "Russian" beads, seemingly not used extensively by dealers but rather by the consumer and by students, are equally valueless. In the Old World, individual types of beads were often called by specific names, but these likewise have no classificatory use. Within the present century, several systems have been devised for bead classification, but so far as the authors are aware, none will permit the identification of each and every glass bead known. The one proposed here will, it is hoped, make good that deficiency, or at least pave the way. It is based on the first hand study of approximately 500 different types, and has been designed to be infinitely extensible.

This classification is based, in the first instance, upon the processes of manufacture; in the second, upon such physical characteristics as shape, size and colour (including translucency and opacity). The last class of attributes encompasses verifiable entities, for it is possible to subject any given specimen to an examination with regard to them, and to compare said specimen with any other bead with respect to each. Processes of manufacture can also be determined by inspection. It should not be inferred from these remarks that the authors imply any sort of evolutionary development in the making of beads, but it is difficult, nevertheless, to see how some of the procedures used could have come into being except through some developmental process such as is outlined below.

The manufacture of glass beads will be discussed more fully in the book which is in preparation: but in order to understand the function of the classificatory system under discussion, it is necessary to have at least some understanding of how beads are made. To this end, the following extremely brief and condensed synopsis of the various processes is given.

Glass, a complicated substance made from silica, an alkali, a stabilizer and (usually) a colouring agent, is molten when raised to a high temperature, and solid at room temperature. In the molten state it is highly ductile, and while cooling can be manipulated into a vast variety of forms by using appropriate techniques. Beads may be made by two principle methods: (1) by drawing out a bubble of molten or viscid glass into a long, slender tube, and (2) by winding threads of molten glass around a wire which is later withdrawn. A third method, probably often used in conjunction with each of the above, is by molding the beads in two-part molds while the glass is still viscid.

The first method of bead manufacture requires the services of two men (Fig. 1). The first man gathers up a small amount of molten glass on the end of his blowing rod, and by blowing into the rod enlarges it to a bubble. He then puts the bubble into the mass of molten glass to gather up more material. At this time, he may either add more glass of the same colour or glass of a different colour from another pot. If a different colour is added, the process is called "layering." Two or more colours may be used, and even five or six layers of different colours are not uncommon. If a simple round tube is required, the second man attaches another iron rod to the far end of the glass bubble, the blower hands his end to a servant and both these men then move in opposite directions until the glass becomes cool and will not pull out further. (In practice, neither of the runners, or tiradors, is the same man as he who withdraws the glass from the furnace and blows it.) The now rigid tube of glass is laid down on slabs of wood to cool (Fig. 1). When it has cooled sufficiently, it is broken up into short lengths, and these are finally chopped into sizes which will serve as beads. It is necessary to note that during the process of drawing, the proportions at any given point along the length of the tube remain constant. This means that the bore is almost uniform throughout, but it becomes smaller and smaller the more slender the tube becomes. We now have cylindrical beads either of monochrome or polychrome glass, depending upon whether one or more layers have been given to the bubble.

1 Drawing a tube for glass beads.

Other treatments than that described above may be given to the bubble. The first of these is the so-called inlay treatment, where "canes" or rods of coloured glass are affixed to it, ultimately producing striped beads. In this process, rods of the required colour are ranged around the inside wall of a pail-like container (Fig. 2). These rods may be themselves either simple or multiple. The bubble is introduced into the centre of the bucket and expanded sufficiently to cause the rods to adhere, whereupon it is re-introduced to the furnace just long enough to cause the rods to coalesce with the surface of the bubble, but not to lose their form. The bubble is then drawn as described above and the resulting tube bears the diminutive remains of the rods on its surface.

2 Inlay treatment for glass beads.

Another treatment may be given on the "marver," or board. The bubble, whether it is layered, unlayered, striped, or a combination of these, is laid on the marver, and either flattened slightly, or paddled to make it triangular, square or some other shape in cross-section. If a corrugated marver is used, the bubble is rolled over it to press the corrugations into the sides. The bubble is then drawn in the usual way. and the finished tube will retain the shape, though not the dimensions given it on the marver. (Generally, when the bubble is rolled on the corrugated marver, it is layered in glass of another colour, and the process is repeated until five or six layers, and in some cases up to twelve, have been built up before it is drawn. The resulting bead is the so-called rosetta, star, or chevron.)

While the tube is being drawn, it may also be twisted. This applies not only to simple monochrome tubes drawn from the bubble as blown, but to layered, inset and marvered beads as well; thus it is possible, and indeed it happens, that one finds such complicated forms as beads which have been layered, striped, squared in section, and twisted.

Some beads, especially large ones, like big chevrons, are often ground at the ends and for a short distance along the sides in order to bring out the colour effects in the layering. Most, however, are not given this rather costly treatment.

Imperfectly shaped beads are not uncommon on Indian sites, and their classification poses a slight problem. Even twinned beads sometimes occur. Generally the intended form is easy to see and they are classified accordingly. It would appear that the Indians were not very critical: in fact, one gets the impression that they actually preferred these eccentric specimens.

The diameter of the finished product will depend entirely on the extent to which the bubble has been elongated; it may vary from an eighth of an inch or less to an inch or even more. When the tubes have cooled, they are broken into long pieces which can later be chopped on a block to the desired length; that is, anywhere from a sixteenth of an inch or thereabouts to three or tour inches. They may either be left in this condition, or they may be subjected to further treatment to reduce them to oval or rounded beads.

To effect this shaping, a mixture of ground charcoal and fine sand is worked into the orifices of the beads, and the whole is then placed in a metal container and re-subjected to heat. In order to keep the beads from fusing together while in this heated condition, the container is constantly agitated on an eccentric axle. This action, in conjunction with the heat, reduces the beads to a round shape, while the mixture of sand and charcoal prevents them from sticking together and the orifices from disappearing. When cool, the beads are separated from the mixture, washed, and then agitated for some time in bags of bran to produce a polished surface.

Whether left in tube form or made into round beads, the finished products are sorted, first on a set of sieves of graded sizes, and finally by hand, during which defective examples are removed. They are then strung into hanks, but nowadays this is less often done than packaging in bulk, in which form they are ready for shipment.

Whereas tube beads are mass produced in the sense that thousands may be made from a single bubble or gathering of glass (which, however, is individually fabricated), wire wound beads are made one by one. Wire which has been covered with chalk, or some similar substance to facilitate removal of the final product, is heated at a flame (originally fed by whale oil) and at the same time a cane or solid rod of glass, about as thick as a lead pencil, is heated and a thread started from it. This thread or strand of molten glass, which may be of any colour, is wound around the wire until a bead of the desired size and shape is built up. Indeed, threads of different colours may be introduced to make multicoloured beads; and glass insets of various kinds, such as simple dots, rosettes, or flowers, may be set into the matrix while it is still soft. Such beads, often called suppialume, are capable of almost infinite variation and attempts to classify them are consequently no more successful than other individually made, handcrafted products.

Although little is known of the process, it is quite apparent that in the past some beads were molded, and it seems safe to assume that this was accomplished in conjunction with the processes outlined above for the making of both tube and wire wound beads. Certainly there are many examples of beads which have been pinched in two-part molds; the so-called "raspberries," "melons," and facetted types being examples of such molded beads.

There is no problem, obviously, in determining when a bead has been molded, but it is not always quite so easy to decide whether a given specimen has been produced by the drawing method or by wire winding. Close inspection with a hand lens will usually reveal this, however, for in the former, the fibres of glass are arranged side by side longitudinally. This is often more clearly shown in tubular beads which have lain in the soil long enough to disintegrate slightly, at which stage the fibres show up quite clearly. In wire wound beads the fibres are arranged in heliacal fashion, round and round the circumference of the specimen. Such an arrangement is often obvious in the so-called milk glass beads. But perhaps of even greater help in deciding the method of manufacture is the presence of small air bubbles. In both processes, these tiny inclusions of air are bound to occur, and it is seldom that inspection will fail to reveal them. In the case of tube beads, little bubbles, like the fibres of glass, have been drawn out into long, thin shapes, a sure indication of the method used to make them. Just as certainly in the case of wire wound beads, the bubbles are either globular or oval and never elongated.

During the 17th, 18th and 19th centuries, the control of the ingredients was a some what haphazard affair for the exact science of chemistry had not yet arisen. The materials which went into the manufacture of glass depended on many variables, but chiefly upon the judgement of the man in charge. It is true that the proportions of the various ingredients which made glass of certain qualities was recognized and followed; but it is equally true that they were not accurately controlled. (A modern analogy would be with a cook who does not follow her recipe exactly in making a cake, but uses her experience and judgement.) Furthermore, the ingredients which went into the glass batch were not chemically pure resulting in considerable variation in the quality of the finished product, some being less stable than others, and so on.

This matter of chemical variation is especially important with regard to colour. It was well understood that certain materials, like copper salts, would produce specific colours; and this knowledge was fully utilized and expanded with increasing experience. But again the colouring chemical was not pure, and slight variations in colour inevitably resulted. Furthermore, the resulting colour could be affected by the nature of the batch into which the chemical was introduced; and if the batch were not uniform in all cases, colour variations could result no matter how pure the pigments were nor how accurately they were measured. All told, therefore, there is room for considerable variation in colour, and 18th century and earlier beads differ considerably in this regard from those made in the 19th and 20th centuries when strict standarization became the rule. In brief, one cannot expect to find consistency of colouring in these early beads; but on the other hand, one does find a rainbow range of beautiful soft colours, very different from the harsh, strident ones so frequently encountered in the modern product.