Venetian beads have been in production since the 1200s, first in Venice and then on the small island of Murano in Italy. There were only a handful of makers who knew the "secret" of the glass bead, and therefore the market was tightly held. Beadmakers were not permitted to share their secrets with others. The business was very lucrative - merchants commissioned and used Venetian beads to purchase many items, including spices and oils.
Essentially there were two types of beads produced - chevron beads and millefiore. Examples of chevron beads are seen below. Individual chevron beads were produced by the "winding" method whereby several layers of glass (usually 7-9) were wound to create a star like pattern. This bead became in such demand that a production process was begun, whereby tubes of beads were created and then cut to produce individual beads.
Photo courtesy of The Bead Chest
Because of the high demand for the beads, production of some beads was actually outsourced to Bohemia (now the Czech Republic). Glass tubes were shipped to Bohemia; the workers would cut the tubes into equally sized beads, and then ship them back to Murano for shaping and polishing! I find this fact quite interesting and think it would be another good topic to research - the history of the czech bead!
I used some information sourced from The Bead Chest - you can find many examples of trade beads including ancient Venetian beads in their store, as well as information on their blog. Below you can see examples of my own modern Venetian bead collection. I purchased these in Venice several years ago. My beads are blown bead (hollows) and also beads that have silver foil as an inside layer. You can also find millefiore and chevron beads today, but I am partial to these ones!
Venetian Bead Shop. You can purchase "venetian" beads in hobby stores or other on-line venues, but you do have to realize that many of them are made in China and won't be genuine Venetian beads, nor will they be annealed or sturdy for your designs.