The Development of Glassmaking in the Ancient World

Overview

Glass is an inorganic solid substance. It is usually translucent, hard, and resists natural elements. While glass occurs naturally, it is one of the most important and oldest manufactured materials in the world. Civilization could not exist as it does today without glass. Glass has important uses in science, industry, work, home, play, and art. A world without glass is virtually inconceivable. In ancient times, glass was used in practical and decorative objects, from which its role in society has evolved into the important status it holds today. Glass is currently used in such diverse applications as housewares, clothing, building construction, and telecommunications.

There is much debate regarding the origin of manmade glass, and the exact date it was first manufactured cannot be accurately assessed. Early man used natural glass, such as obsidian, for making sharp tools used for cutting and hunting. It is believed that the first objects manufactured entirely from glass originated in Mesopotamia around 2500 b.c. While most of the artifacts from that time consisted of beads, some of the earliest glassware, in the form of sculpted vessels, still survives into modern times and is speculated to come from Mesopotamia. It has been surmised that they were used for oils and cosmetics of nobility. Glassmaking techniques eventually radiated from Mesopotamia into other geographical areas, bringing the technology to new regions of the world.

Small glass vessels that were sculpted directly from blocks of glass have been found with other Egyptian artifacts, indicating that they had this technology as much as 4,000 years ago. A glass bottle bearing the sign of Thutmose III, a pharaoh of the eighteenth dynasty of Egypt, is on display in the British Museum in London. The Egyptians, who set the early standard in glass-making, also used glazes of glass to embellish objects made of other material. In time, glassmaking skills spread throughout the known world and became important to many societies.

Background

Perhaps the first notable advancement in glass-making technology was that of the millefiori process for making open beakers and shallow dishes. The process originated around 100 b.c. in Alexandria and consisted of a shaped core over which sections of colored glass were overlaid. Later, an outer mold was placed over the glass to maintain the shape during the baking process. The pieces of glass fused together in the oven and the glass was then ground smooth. The finished project was both beautiful and practical.

Before the turn of the millennium, the Phoenicians introduced the new technique of blowing glass. They used a form of glass that had a consistency that was well suited for this type of work. In this process, a blowing iron was used to shape and mold molten glass. This was an iron tube about 39-79 in (1-2 m) long consisting of a mouthpiece at one end and a wider knob for holding the soft glass at the other. The craftsman loaded molten glass at one end and rolled it into shape on a hardened surface called a marver. The softened glass could also be blown from the opposite end into a mold or blown freely in the air. Subsequent trials of molding and reheating would allow the craftsman to shape the glass into the desired configuration. He also made use of a solid iron rod, called the pontil, that was used to help sculpt the glass. More complex features, such as a handle, could also be added whenever the craftsman desired.

The technique of blow molding spread rapidly through the known world. Skilled craftsman would readily go wherever they thought there was a suitable market for their skills. Glass engraving took root in Italy where they made cameo glass. This technique involves grinding through an opaque white outside layer to an inner darker region, which leaves a silhouette. The most famous example of this exacting technique is the Portland vase now on display in the British Museum, London. It was the Romans, however, who took the lead in the glassmaking industry.

The Romans used the glass blowing procedure for shaping glass, which made it possible to manufacture low cost, high quality decorative glassware. The Romans were also the first to produce a glass that was relatively clear and free of most impurities. Glass objects were then available to almost all strata of society. They made various objects such as bowls, bottles, and lamps. The Roman artisans took their craft very seriously and their work became the world standard. Glassmaking became such a lucrative field in Rome that all glassmakers paid heavy taxes.

Early forms of glass consisted of three major components: lime, silica, and soda. Any impurities within the mix would cause the glass to become opaque or colored. Both the Romans and Egyptians probably mixed sand, ground seashells, and hardwood ash as sources of silica, lime, and soda, respectively. In order to color the glass, they added various metallic oxides. For example, copper was used to make green or ruby colored glass. It is noteworthy that these techniques depend on precise measurement of the metallic oxides and the early glassmakers were remarkably consistent in their colors and tints.

As successful as the Romans were in many glassmaking areas, they were never successful in producing flat slabs of glass, such as those now used in windows. They could not achieve a transparent pane without an enormous amount of labor to polish and grind the glass. The difficulty in reproducing adequate panes of glass eventually lead to the widespread use of the stained glass window.

The fall of the Roman Empire lead to a decline in glassmaking craftsmanship in the Western world, but the industry continued to thrive in the Near East. Outstanding examples of both highly technical and artistic forms of glass were made in this part of the world through the Renaissance.

Another important advancement in technology, which did not occur until the latter stages of antiquity, was the invention of the bellows. Bellows are mechanical devices that increase the air pressure within the device so that it can expel a jet of air. They usually consist of a hinged container with flexible sides that expand the volume of the container to draw air in and then compresses the volume to expel air out. These devices are used to stoke a fire, which results in an increased speed of combustion so the fire burns hotter.

Impact

The introduction of manufactured glass into society has been beneficial to mankind. We now rely heavily on glass in modern times. In the form of windows, glass has the obvious dual qualities of letting light into a room while protecting that room from extreme weather at the same time. Glass is used in lights, televisions, mirrors, optics, and telecommunications. In many works of art, it is a necessary component. Glass is extremely durable, although subject to breakage with sharp forces. It is nonporous, does not retain odors, and can be completely sterilized. It is absolutely essential to our modern way of life. Those early glassmakers are owed a debt of gratitude for the constant development of their craft.

The principle reasons behind the widespread use of glass is its flexibility in terms of use and manufacture, and the low cost at which it can be produced. Raw materials for the process are inexpensive and abundant so that most objects can be mass produced at a reasonable cost.

The most significant advancement in glass-making technology was that of blow molding, which had a tremendous impact on society and could be considered one of the greatest technical innovations in history. This enabled humans to mold molten glass into virtually any desired size and shape. Glass ranges in size from extremely small fiber optics (less than 1/100,000 of a meter) to the extremely large reflecting mirror of the Hale telescope (more than 16.4 feet [5 m]).

Glassblowing made possible new commercial applications of glass and resulted in the creation of high quality pieces of art. Much of our modern glassblowing techniques rely on technology that had already been developed by the a.d. 300. Glassblowing gave craftsman remarkable control over their work, yet at the same time yielded an infinite variety of potential shapes and sizes. These pieces could be made at a relatively low cost and helped to set the course for our heavy reliance on an inexpensive, but practical commodity.

The immediate social impact of improved glassmaking was that glass goods, previously available to only the upper class, could be obtained by virtually everyone. Important, useful household items such as bottles and lamps became a mainstay of every home. It also provided those societies that developed and exported glass, an important commodity to trade, with great economic benefits as well. Glass had a tremendous positive influence on earlier societies, but has special relevance in modern times because it is incorporated into all facets of society. It is truly one of the most important manufactured products.

JAMES J. HOFFMANN