Seed beads or rocailles are uniformly shaped, spheroidal beads ranging in size from under a millimeter to several millimeters. Seed bead is also a generic term for any small bead. Usually rounded in shape, seed beads are most commonly used for loom and off-loom bead weaving. They may be used for simple stringing, or as spacers between other beads in jewelry.
Larger seed beads are used in various fiber crafts for embellishment, or crochet with fiber or soft, flexible wire. The largest size of a seed bead is 1° (“one-aught”, sometimes written 1/0) and the smallest is 24°, about the size of a grain of sand. However, beads that are size 5° or 6° are usually called “pony beads” rather than “seed beads”; the next larger class of seed beads, from 3° to 4°, are usually called “trade beads”; the largest class of seed beads, including 1°, 2°, and anything larger, are usually referred to as “crow beads.”
Most modern seed bead work is done using beads ranging in sizes 6°, 8°, 11°, 12°, 13° and 15°. Sizes 6°, 8° and 11° are often used in beaded knitting, as well as bead knitting. The extremely small class of seed beads smaller than 15° have not been in production since the 1890s and any in existence are usually considered antiques.
The very small holes in the centers of most seed beads means that stringing them usually requires the use of a specialized long narrow needle called a beading needle.
Two principal techniques are used to produce seed bead: the wound method and the drawn method. The wound method is the more-traditional technique, is more time consuming, and is no longer used in modern bead production: in this technique, a chunk of glass known in glassmaking as a gather and composed mainly of silica is heated on an iron bar until molten. A second bar of iron is then inserted into the gather and the two bars quickly drawn apart creating a long glass rod (the final width of which would depend on how quickly and how far the bars are separated before the glass solidifies).
This rod is then cut into shorter rods for handling. Next, one of these is re-heated and wound around a hot metal wire creating a ring of glass which is then worked and shaped until smooth and round. This is done several times on the same wire creating a series of glass rings. Once the wire cools, the rings are slipped off and then used as beads. For the drawn method, an air bubble is created within the gather and as the iron bars are drawn apart they produce a long tube rather than a rod. This tube is then cooled, cut into rings, and the rings are tumbled to remove sharp edges before being used as bead.