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Semiprecious Gems: Glass Beads & Jewelry Glass



The History of Jewelry Glass

The first use of "glass" by early man was in the carving and shaping of simple cutting tools, made with a naturally-occurring volcanic mineral known as obsidian. This opaque black material was ideally suited for the making of sharp objects due to its conchoidal fracture, which facilitates the "sharpening" of obsidian (glass) to near molecular thinness. The word "glass" was derived from the Latin term glesum, and the Germanic word glessum, both referring to the transparent material known as amber.



The making of glass did not take place until around 3500 BC, and its earliest use was in the regions of ancient Canaan (Syria), Egypt, Mesopotamia and the Indus Valley. Early glass was used as a gem simulant, which was significantly easier to carve and shape than its natural counterparts.


Ancient Glass Making

Originally, glass may have been discovered by accident, occurring as a curious byproduct during the making of glazed ceramic (faience ware) beads, or as a vitreous byproduct of the metal smelting process. Predating the invention of glass beads, so-called "crumb bead" were a mixture of faience, soapstone particles and cement [4]. The manufacturing of glass took a significant leap forward during the Late Bronze Age (c.1500 BC) with the Mycenae (c. 1600-1100 BC) and Phœnician (c. 1500-300 BC) civilizations.

Ancient glass was made with a combination of silicon dioxide (common sand); calcium carbonate (limestone, calcite, aragonite or sea shells); and sodium carbonate (soda ash). Sodium carbonate is an alkali that was extracted from evaporites (mineral deposits resulting from seasonal lake evaporation), or from the ashes of Salsola kali (saltwort), which is a arid, salt-loving plant (halophile) that grows along the seashore in Syria and Lebanon. The word "alkali" is derived from the Arabic word al qaly, meaning "from kali." Alkali is also used to make soap, which is another ancient commodity of this region.


Ancient Glass Bead Jewelry

Ancient Glass Beads c. 300 BC

   Phoenician Glass Beads

Phœnician Glass Beads c. 800 BC


Glass is made when sand, soda ash and lime are heated to a high temperature (750C to 1000C), then rapidly cooled to a hardened state forming glass ingots. The first techniques for the creation of glass objects were the "core-forming" technique which was used to make glass vessels (amphora, amphoriskos, or aryballos), and the "wound bead" technique for the making of glass beads.

Core-forming and wound-bead flamework involved the use of a "beehive" furnace; a wood combustion source; molten sand, soda ash, and lime, heated in a ceramic crucible; and a metal "mandrel" to draw the ductile "rope" of molten glass around a copper rod (for beads) or a pre-shaped mold of the intended vessel made of hardened clay and dung [6]. The core-wound material was then reheated several times in the "fusing" process. Core-forming was the precursor for the glass-making technique known as "lampworking," which only used a single flame (lamp) as a heat source.

The earliest examples of ancient glass were very crude, suitable only for being carved or ground into beads or gem simulants using conventional lapidary techniques (cold working) As techniques advanced however, the glass grew increasingly transparent making it suitable for a variety of applications. The Phœnician and Egyptian glass-making methods soon spread, and Etruscan, Greek and Roman artisans all became accomplished in the production of glass amphorae, beads, and figurines. Glass-making also spread to Bohemia, ancient China, India and Japan.


Adding Color to Ancient Glass

Ancient glass was either colored inadvertently, by impurities within the basic batch of ingredients, or intentionally, using metallic oxides (pigments) to impart a color throughout to mixture. Color can also be affected by the absence, or presence of oxygen in the furnace. Some of the pigments used in the making of glass were also used to make cosmetics and paints.

Pigments that were used to add color to glass needed to have a high level of heat stability in order to withstand the temperatures in the furnace. Cobalt was used to achieve a deep azure blue, copper and/or iron were used for turquoise-blue, antimony and lead were used of yellow, oxides of copper were used for orange and red, and manganese salts were used to create the color violet. Milk-white glass was made using tin and/or lead oxide, and black glass was made with a combination of copper, manganese, and ferric iron.


Roman Glass Beads

Roman Glass Beads c. 200 BC

   Phoenician Glass Beads

Bactrian Gabri glass beads


Another technique which was employed to make multicolored beads and vessels was "flameworking." In this process, pre-made tubes or rods of colored glass (cane) were melted onto the surface of the existing glass bead or vessel to create a polychrome design. While the colored glass rods were still in a molten state they were worked with a metal pin to create patterns and designs. A metal comb could also be drawn across the rods to create vertical ribs.


Lampworking

The glass-making technique known as "lampworking" (aka: flameworking, torchworking) is an offshoot of the ancient core-forming technique, but instead of a beehive furnace, the soda-lime glass or lead glass rod is heated using an oil-burning lamp with a glass chimney, called an "argand lamp." Once in a molten state, the glass beads are shaped around a metal core using a combination of heat, gravity and manipulation by pressing the bead, or using tools such as paddles, mashers, picks or tweezers.


Lampwork Glass Beads

Lampwork glass beads

   Recycled Roman Glass

Modern Jewelry with recycled Roman glass


The exact date of lampwork's invention is not known, but it is generally attributed to the medieval period. During the Dark Ages about the only demand for objet d'art was coming from the Catholic Church, so glass beadwork production was primarily limited to rosaries.

After the initial shaping of the bead, it can be decorated by applying molten fibers (stringers) on the bead's surface, creating dots or lines. Intricate patterns and designs can be made with the use of a sharp tool. When the design work is finished the bead needs to go through the annealing process where it is reheated to around 1000F to reach the proper "stress relief" point. Lampwork beads can also be sandblasted or faceted using conventional lapidary techniques.


Romanian Glass Bead Jewelry

Bohemian glass bead jewelry from Romania

   Murano Millefiori Glass Paperweight

Murano millefiori glass paperweight


The exact date of lampwork's invention is not known, but it is generally attributed to the medieval period. During the Dark Ages about the only demand for objet d'art was coming from the Catholic Church, so glass beadwork production was primarily limited to rosaries.

The lampworking method reached its zenith during the 14th century in Murano, Italy. During the Renaissance period in Murano, artisans melted the colored-glass rods with a oil-fueled torch. With the glass in a molten state, it is formed by blowing on it, or shaping it with a combination of tools and hand movements. When multiple colored-glass canes are fused together in a "bar," they can be used to create "millefiori glass," which is still used in the making of jewelry glass and glass paperweights.


Bohemian & Czech Glass Beadwork

So-called "bohemian glass" (aka: bohemia crystal) is a grind-decorated or cold-worked glass that was made in Bohemia (present-day Czech Republic) and Silesia (present-day Poland near Wroclaw) since the 13th century. No one is more famous in the world of Bohemian glass than Leopold (1822-1895) and Rudolf Blaschka (1857-1939). Rudolf Blaschka was originally trained in the craft of art glass while living in Venice, Italy, but moved to Northern Bohemia in 1822 [9].


Czech Glass Bead Jewelry

Czech glass beads

   Murano Glass Bead Necklace

Murano glass bead necklace


When the gem faceting craze swept across Europe in the late 13th and early 14th centuries, glass was once-again used as a gem simulant. Glass was faceted to look like an actual gem, using typical lapidary methods, until the invention of the machine-made "Czech glass bead" in the 19th century. Responding to the perennial need for affordable jewelry, these mass-produced, "faceted" glass gems were an immediate sensation. The Czech glass method involves pressing hot glass into a heated mold, which produces identical copies by the thousands. Gold or bronze-tone finishes are then added by coating the beads with heated metals.


Cameo Glass

Another glass gem-simulant of the 19th century was "cameo glass," which was made to simulate the stratified layers of natural sardonyx. With cameo glass, one color of glass would be applied to another contrasting color, creating an outer layer that would then be carved away, or acid-etched to reveal the darker background color.


21st Century "Dichroic Glass" Beads & Gems

Dichroic glass, of "fusion glass" is new type of glass bead or gem that is made from techniques that were developed by NASA, as part of their research for the space program. The name relates to the effect of dichroism, which causes the glass to change colors when viewed from different angles. Dichroism also causes a rainbow effect on the glass surface.


Dichroic Glass Base

Dichroic glass base

   Fusion Glass Bead

Dichroic FusionGlass beads


The dichroic effect is created on the "base glass" by depositing thin film layers of metal oxides such as cobalt, magnesium, silicon and titanium. By combining different types of base glass in the form of powders, confetti, or noodles, a layering effect takes place making each piece a unique creation.








Bibliography on Glass in Jewelry and Ancient Glass Beads


1. The Bead Study Trust . www.beadstudytrust.org.uk

2. Encyclopedia Phoeniciana, Phoenicianan Crafts . www.phoenicia.org

3. Three kinds of Phoenician glass . www.cartage.org.lb

4. F. Rogers, A. Beard, 5000 Years of Gems & Jewelry. FA Stokes Co., N.Y.

5. The Corning Museum, Glass Dictionary . www.cmog.org

6. Robert A. Mickelsen, Art Glass Lampwork History . www.theglassmuseum.com

6. Glass Making: The Life of Ancient Egyptians . www.touregypt.net

7. Beverly Fernandes, History of Czech Glass . www.harlequinbeads.com

9. The Blaschkas: Glass Designer-Makers . www.designmuseum.org

10. The International Society of Glass Beadmakers . www.isgb.org

11. Dichroic Fusion Glass . www.fusionglassco.com





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