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Glassblowing is a glassforming technique that involves inflating molten glass into a bubble (or parison) with the aid of a blowpipe (or blow tube). A person who blows glass is called a glassblower, glassmith, or gaffer. A lampworking (often also called a glassblower or glassworker) manipulates glass with the use of a torch on a smaller scale, such as in producing precision laboratory glassware out of borosilicate glass.
To increase the stiffness of the molten glass, which in turn makes the process of blowing easier, there was a subtle change in the composition of glass. With reference to their studies of the ancient glass assemblages from Sepphoris. postulated that the concentration of natron, which acts as flux in glass, is slightly lower in blown vessels than those manufactured by casting. Lower concentration of natron would have allowed the glass to be stiffer for blowing.
During blowing, thinner layers of glass cool faster than thicker ones and become more viscous than the thicker layers. That allows production of blown glass with uniform thickness instead of causing blow-through of the thinned layers.
A full range of glassblowing techniques was developed within decades of its invention. The two major methods of glassblowing are free-blowing and mold-blowing.
Researchers at the Toledo Museum of Art attempted to reconstruct the ancient free-blowing technique by using clay blowpipes. The result proved that short clay blowpipes of about facilitate free-blowing because they are simple to handle and to manipulate and can be re-used several times. Skilled workers are capable of shaping almost any vessel forms by rotating the pipe, swinging it and controlling the temperature of the piece while they blow. They can produce a great variety of glass objects, ranging from drinking cups to window glass.
An outstanding example of the free-blowing technique is the Portland Vase, which is a cameo manufactured during the Roman period. An experiment was carried out by Gudenrath and Whitehouse with the aim of re-creating the Portland Vase. A full amount of blue glass required for the body of the vase was gathered on the end of the blowpipe and was subsequently dipped into a pot of hot white glass. Inflation occurred when the glassworker blew the molten glass into a sphere which was then stretched or elongated into a vase with a layer of white glass overlying the blue body.
Two types of mold, namely single-piece molds and multi-piece molds, are frequently used to produce mold-blown vessels. The former allows the finished glass object to be removed in one movement by pulling it upwards from the single-piece mold and is largely employed to produce tableware and utilitarian vessels for storage and transportation.Tatton-Brown, V. (1991). "The Roman Empire". In H. Tait (ed.) Five Thousand Years of Glass. pp. 62–97. British Museum Press: London Whereas the latter is made in multi-paneled mold segments that join together, thus permitting the development of more sophisticated surface modeling, texture and design.
The Roman leaf beaker which is now on display in the J. Paul Getty Museum was blown in a three-part mold decorated with the foliage relief frieze of four vertical plants. Meanwhile, Taylor and HillTaylor, M. & D. Hill 1998. Making Roman Glass Today. In The Colchester Archaeologist 11 tried to reproduce mold-blown vessels by using three-part molds made of different materials. The result suggested that metal molds, in particular bronze, are more effective in producing high-relief design on glass than plaster or wooden molds.
The development of the mold-blowing technique has enabled the speedy production of glass objects in large quantity, thus encouraging the mass production and widespread distribution of glass objects.Cuneaz, G. (2003). "Introduction". In R.B. Mentasti, R. Mollo, P. Framarin, M. Sciaccaluga & A. Geotti (eds.) Glass Through Time: history and technique of glassmaking from the ancient world to the present. pp. 11–30. Skira Editore: Milan
Glassblowing involves three furnaces. The first, which contains a crucible of molten glass, is simply referred to as "the furnace". The second is called the "glory hole", and is used to reheat a piece in between steps of working with it. The final furnace is called the "lehr" or "annealer", and is used to slowly cool the glass, over a period of a few hours to a few days, depending on the size of the pieces. This keeps the glass from cracking or shattering due to thermal stress. Historically, all three furnaces were contained in one structure, with a set of progressively cooler chambers for each of the three purposes.
lampworking, usually but not necessarily work on a much smaller scale, historically using alcohol lamps and breath- or bellows-driven air to create a hot flame at a workbench to manipulate preformed glass rods and tubes. These stock materials took form as laboratory glassware, beads, and durable scientific "specimens"—miniature glass sculpture. The craft, which was raised to an art form in the late 1960s by Hans Godo Frabel (later followed by lampwork artists such as Milon Townsend and Robert Mickelson), is still practiced today. The modern lampworker uses a flame of oxygen and propane or natural gas. The modern torch permits working both the soft glass from the furnace worker and the borosilicate glass (low-expansion) of the scientific glassblower. This latter worker may also have multiple headed torches and special lathes to help form the glass or fused quartz used for special projects.
Hence, tube blowing not only represents the initial attempts of experimentation by glassworkers at blowing glass, it is also a revolutionary step that induced a change in conception and a deep understanding of glass.Israeli, Y. (1991). "The Invention of Blowing". In M. Newby & K. Painter (eds.) Roman Glass: Two Centuries of Art and Invention. pp. 46–55. The Society of Antiquaries of London: London Such inventions swiftly eclipsed all other traditional methods, such as casting and core-forming, in working glass.
Evidence of glass blowing comes even earlier from the Indian subcontinent in the form of Indo-Pacific beads which uses glass blowing to make cavity before being subjected to Tube drawing for bead making dated more than 2500 BP. Beads are made by attaching molten glass gather to the end of a blowpipe, a bubble is then blown into the gather.
Ennion for example, was among the most prominent glassworkers from Lebanon of the time. He was renowned for producing the multi-paneled mold-blown glass vessels that were complex in their shapes, arrangement and decorative motifs. The complexity of designs of these mold-blown glass vessels illustrated the sophistication of the glassworkers in the eastern regions of the Roman Empire. Mold-blown glass vessels manufactured by the workshops of Ennion and other contemporary glassworkers such as Jason, Nikon, Aristeas, and Meges, constitutes some of the earliest evidence of glassblowing found in the eastern territories.Hőricht, L.A.S. (1991). "Syrian Elements among the Glass from Pompeii". In M. Newby & K. Painter (eds.) Roman Glass: two centuries of art and invention. pp. 76–85. The Society of Antiquaries of London: London
Eventually, the glassblowing technique reached Egypt and was described in a fragmentary poem printed on papyrus which was dated to the 3rd century AD.Coles, R.A. 1983. The Oxyrhynchus Papyri 50. Egypt Exploration Society for the British Academy: London. The Roman hegemony over the Mediterranean areas resulted in the substitution of glassblowing for earlier Hellenistic casting, core-forming and mosaic fusion techniques. The earliest evidence of blowing in Hellenistic work consists of small blown bottles for perfume and oil retrieved from the glass workshops on the Greek island of Samothrace and at Corinth in mainland Greece which were dated to the 1st century AD.
Later, the Phoenician glassworkers exploited their glassblowing techniques and set up their workshops in the western territories of the Roman Empire, first in Italy by the middle of the 1st century AD. Rome, the heartland of the empire, soon became a major glassblowing center, and more glassblowing workshops were subsequently established in other provinces of Italy, for example Campania, Morgantina and Aquileia. A great variety of blown glass objects, ranging from unguentaria (toiletry containers for perfume) to cameo, from tableware to window glass, were produced.
From there, escaping craftsmen (who had been forbidden to travel) otherwise advanced to the rest of Europe by building their glassblowing workshops in the north of the Alps (which is now Switzerland), and then at sites in northern Europe in present-day France and Belgium.Allen, D. (1998). "Roman Glass in Britain". Shire Archaeology No. 76. CTT Printing Series Ltd.: Pembrokeshire.Price, J. (2000). "Roman Glass Production in Western Europe". In M-D Nenna (ed.) La Route Du Verre: ateliers primaries et secondaires du second millenaire av. J-C au Moyen Age. pp. 123–124. Maison de l’Orient Mediterranean: Paris
One of the most prolific glassblowing centers of the Roman period was established in Cologne on the river Rhine in Germany by the late 1st century BC. Stone base molds and terracotta base molds were discovered from these Rhineland workshops, suggesting the adoption and the application of mold-blowing technique by the glassworkers. Besides, blown and blown jars decorated with ribbing, as well as blown perfume bottles with letters CCAA or CCA which stand for Colonia Claudia Agrippiniensis, were produced from the Rhineland workshops. Remains of blown blue-green glass vessels, for example bottles with handles, collared bowls and indented beakers, were found in abundance from the local glass workshops at Poetovio and Celeia in Slovenia.Lazar, I. 2006. Glass finds in Slovenia and neighbouring areas. In Journal of Roman Archaeology 19: 299–342.
Surviving physical evidence, such as blowpipes and molds which are indicative of the presence of blowing, is fragmentary and limited. Pieces of clay blowpipes were retrieved from the late 1st century AD glass workshop at Avenches in Switzerland. Clay blowpipes, also known as mouthblowers, were made by the ancient glassworkers due to the accessibility and availability of the resources before the introduction of the metal blowpipes. Hollow iron rods, together with blown vessel fragments and glass waste dating to approximately 4th century AD, were recovered from the glass workshop in Mérida of Spain, as well as in Salona in Croatia.
The Nøstetangen Museum at Hokksund, Norway, shows how glass was made according to ancient tradition. The Nøstetangen glassworks had operated there from 1741 to 1777, producing table-glass and chandeliers in the German and English styles. Nøstetangen Glassworks (Nøstetangen) . nostetangenmuseum.no Gamle Sorenskrivergaarden (Nøstetangen) . nostetangenmuseum.no
Working with large or complex pieces requires a team of several glassworkers, in a complex choreography of precisely timed movements. This practical requirement has encouraged collaboration among glass artists, in both semi-permanent and temporary working groups.
In addition, recent developments in technology allow for the use of glass components in high-tech applications. Using machininery to shape and form glass enables to manufacture glass products of the highest quality and accuracy. As a result, glass is often used in semiconductor, analytical, life science, industrial, and medical applications.( Thermal Processing of Precision Glass (LouwersHanique))
The subject of mystery novelist Donna Leon's Through a Glass, Darkly is the investigation of a crime in a Venetian glassworks on the island of Murano.
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