Glass (8/31/2017)
Construction Notes spent the summer learning new and fascinating information about glass and windows (as well as juvenile justice and clinical education) that I will share with you in this and other Construction Notes. But first, let me catch you up on all of the work that has been going on since May.
When we left for the summer, slabs and columns were being poured for the garage and for the foundations of 250 Massachusetts Avenue. That excavation continued throughout the summer and has now moved farther south. The ramps from the old highway entrance and exit have been demolished and piles and lagging boards are now installed almost to F Street. Tiebacks are being installed on several levels of the support walls to further stabilize the soil. Columns are rising and concrete slabs have been poured for the P-2 level of the parking garage. Concrete pours for the P-1 level slab begin this week.
Exhaust fans are being installed and tested in the North Tunnel. Surface hardscape and utility work continues along H Street and on Massachusetts Avenue. Curbs and gutters are being installed and sections of streets and sidewalks are being paved on H Street and Massachusetts. New street lights and traffic signals are popping up at various locations.
The area behind Holy Rosary Church has been cleared for the eventual construction of a new Church Rectory, an addition to the Casa Italiana Cultural Center, and a new plaza behind the buildings for the congregation to gather and celebrate. One of the more interesting aspects of this sub-project is the strengthening of the foundation that supports the Campanile — the freestanding bell tower attached to the back of the church. The Campanile was built in 1942, almost 20 years after the construction of the church. The bells, however, were not installed at that time because of metal shortages during World War II. The five bells finally called the parishioners of Holy Rosary to services in 1947.
When Capitol Crossing is completed, a garage will exist deep below the ground adjacent to the Campanile. To support the tower, its mat foundation will be extended downward through the use of underpinning pits to a point fifty-eight feet deeper than the mat-slab that currently supports the tower. Digging the garage to that depth would normally undermine the soil that supports the Campanile. To support the tower and retain the soil, seventeen underpinning pits are being dug, some beneath the Campanile, some on the east side of the church, and others on the south side of Casa Italiana. Before the pits are dug, outcroppings must be cut from the tower mat-slab since they would otherwise extend into the plane of the new garage and Rectory. Holes are being drilled into the mat-slab so that a concrete wire-saw can be inserted to cut the slab flush with the face of the tower. Once the slab section is removed, workers begin to dig the pits.
The pits or shafts are generally 3 three-feet by five-feet and range from eight and a half to slightly more than sixty-one feet deep. Interestingly, they are dug by hand. A worker slowly digs his way down a “reinforced” shaft and fills a bucket with excavated earth which is then pulled to the surface by rope and pulley. The reinforcement consists of lagging boards placed around the perimeter of the excavation to prevent dirt walls of the pit from collapsing into the hole as the worker removes the soil. It usually takes a day to remove four feet of soil. Once the pit reaches its maximum depth, concrete will be forced into the shaft. When completed, the underpinning pits support the weight of the bell tower and transfer the load — the weight of the tower — down to the earth below. The pits retain the soil under the church and provide a sturdy and safe support for the Campanile.
The intricacies and oddities of a construction project often raise questions from the casual observer. Some of you have asked about the box-like coverings on the platform. Those structures cover columns, utility penetrations, vents, and elevator pits that await construction of future buildings. Otherwise, the surface of the platform is virtually complete. Others of you have asked about the larger concrete block structures that now rest on the platform. Those structures provide sheltered emergency exit stairways from the highway below. These exits will be inside later-constructed buildings.
A third question concerns the concrete tub-like structures on the northeast and northwest corners of 200 Massachusetts Avenue. Fondly called the “birdbaths” by the crew, they are part of the air intake and exhaust systems for the restaurants and other tenants that will occupy the building. In non-glass curtain-wall buildings, internal air is removed through ducts leading to penetrations in the building wall. That can’t be done with a glass curtain-wall so other means must be devised. In this case, one birdbath is used for air intake and the other for exhaust. Outside air will enter one of the hollowed-out birdbaths and be spread throughout the building via ducts in the ceilings and walls. Other ducts will send the internal air to the other hollowed-out structure where it will escape through a grill at the top. Because the grills on both units sit outside the curtain wall, water can collect in the tub-like birdbath. That water will escape through drains set in the bottom of the unit and eventually flow into the sewer.
Inside the building, work continues on many facets of the construction. Several elevator doors have been installed and bathroom mock-ups are now in place. Electrical conduit, plumbing lines, and ductwork run throughout the building. I will write more about that in a later Construction Note. But for now, it is the windows rising on the building at 200 Massachusetts Avenue that catch our eye.
Windows are seemingly everywhere in modern life. The double-hung sash and casement windows of our homes, the storefronts that enliven our commercial corridors, and stunning and soaring design windows like those that billow out like blue-green sails from the National Association of Realtors on New Jersey Avenue add to our comfort, beckon us outward or inward, and play with our senses of sight and touch. Similar soaring windows will soon encase the first of two, and ultimately five, glass curtain-wall buildings of the Capitol Crossing project. Before we left for the summer, just over twenty windows had been installed on the building. Today, eight hundred and seventy-eight windows adorn the sides of 200 Massachusetts Avenue. They are being installed at a rate of one hundred and forty-eight per week. By mid-October all of the upper-floor windows will be in place.
The world’s love affair with windows and light is relatively new. Technological advances in the 19th century permitted architects to increase the use and size of glass windows in buildings in England and Germany, leading ultimately to buildings that are seemingly made of windows today. But the ancient world, at the mercy of weather and disease, stench, war, and spirits, eschewed the use of windows altogether. Visible and invisible enemies hovered everywhere, sometimes taking lives often without warning or explanation. Early men and women sought to seal themselves off from strangers and strange vapors rather than invite them in. The prophet Jeremiah, for example, warned that “death has come into our windows and entered our palaces.” One Middle Eastern legend tells that Baal, the Canaanite god of fertility, objected to windows in his palace. After his arrogant designers ignored his warnings, Mot, the god of sterility, entered the palace “doing great harm.”
Today it is impossible to separate discussions of windows from a discussion of glass. But that was not always the case. Glass, the dominant feature of the Capitol Crossing buildings, is defined by the Oxford English Dictionary as “a hard, brittle substance, typically transparent or translucent, made by fusing sand with soda ash and lime [under heats as high as 1,550 degrees centigrade] and [then] cooling [it] rapidly.” But hard science falls short of describing the human experience of glass. Antonio Neri, a 17th century Florentine priest called glass the “fruit of the art of fire.” He went on to say that “Glass is more gentle, graceful, and noble than any other metal and its use more delightful, polite, and sightly than any other material.”
What makes glass special and different from other materials is its crystal structure at the molecular level. Due to the intense heat applied and the extremely rapid cooling during the glassmaking process, its molecular structure freezes when glass is neither liquid nor solid, leaving it to be suspended somewhere in between. Heat it again, and it reverts to a viscous liquid. Though most glass is man-made, it also occurs naturally during volcanic eruptions or when highly-charged lightning strikes sand. Most commonly, natural glass is found as obsidian, a glass created by volcanos via the same intense heat and rapid cooling principles.
No one knows who invented glass, but some legends and early historians attribute its discovery to Phoenician sailors. Although some shapeless lumps of glass have been found in Mesopotamia dating from 2500 B.C.E., the oldest known reference to man-made glass comes from the Historia Naturalis written by Pliny the Elder sometime around the year 77 B.C.E. Pliny wrote that “there is a story that once a ship belonging to some traders in natural soda put in here and that they scattered along the shore to prepare a meal. Since, however, no stones suitable for supporting their cauldrons were forthcoming, they rested them on lumps of soda from their cargo. When these became heated and completely mingled with the sand on the beach a strange translucent liquid flowed forth in streams; and this, it is said, was the origin of glass.” Historians believe that Pliny wrote this while on the coast below Mount Carmel in what is now Israel near the city of Haifa. The region just inland has been a major center of raw glass production throughout history, with both written and archaeological evidence supporting its importance.
Pliny’s origin fable hints at many important aspects of early glass production and offers an explanation of innovation as a happy accident. Charming though this tale may be, it is considered a bit simplistic today. Archaeologists have shown that glass existed before the Phoenicians appeared to dominate trade throughout the Mediterranean world.
To understand new materials, particularly pyro-altered ones like glass, it is helpful to trace their evolution by looking at predecessor materials and the technologies that were used to produce them. Anyone who visits a museum is likely to have seen early glassious artifacts — that is, items whose crystal structure attains glass-like properties during the cooling process — without realizing they are looking at a form of glass. Walking through an exhibit of ancient Egyptian artifacts, one will likely see many small, brightly-colored deity statues and amulets made of a material called faience. This non-translucent material lacks the attributes we ascribe to glass today, but chemically speaking, it is not so different. It is made from sand, soda, and lime paste which are then fired to create a smooth and shiny surface caused by the glassious crystal structure formed at a molecular level. That crystal structure, however, forms only on the surface of the material, not all the way through. Early Egyptian craftsmen lacked the requisite firing temperatures and methods to make glass as we know it, but the technology they used to make faience formed the basis for its later inception.
The earliest man-made glass artifacts were beads used for Egyptian royal jewelry. The first glass vessels also appeared in Egypt, likely due to its sophisticated faience industry and access to the needed material. The earliest surviving piece of glassware from Egypt bears the name of Pharaoh Thutmose III who ruled from 1504 to 1450 B.C.E. Historians believe that Thutmose captured glass makers on one of his military campaigns to Mesopotamia and brought them to Egypt to make true glass — hence his name appears on the earliest known piece. Archaeologists have also found the ruins of a glassmaking factory in an Egyptian industrial complex dating from the reign of Rameses the Great. The eastern Nile delta site, known as Qantir-Piramesses, flourished in the 13th century B.C.E. as the northern capital of the pharaohs.
The earliest type of soda used in the production of glass is a naturally-occurring substance called natron that is widely available from dried lake beds in Egypt and in parts of the Near East. It is likely the kind of the soda mentioned by Pliny. The technology began by simply combining the natron with lime and sand to create a translucent blue viscous substance which was then poured onto overturned ceramic bowls, thus creating a glass vessel. This new material was widely coveted for a variety of reasons and its use spread throughout the Mediterranean world. The Phoenician opened up access to natron, allowing glass production to spread to all of their trading regions. New techniques, such as glass blowing, allowed for the fabrication of more complex objects, while the addition of minerals allowed for decorative coloration.
Glass production declined in Egypt around 1070 B.C.E. as the kingdom collapsed; but it reappeared in western Asia and in the Mediterranean world between 900 and 300 B.C.E. In the early days of the Roman Empire, glass objects were luxury items because they were made slowly and could not be produced in large quantities. Artisans had limited techniques and so a simple bottle could take days to make. Around 50 B.C.E., the Romans had learned (probably from the Greeks and most likely from Crete) how to gather molten glass on the end of a pipe and inflate it. Free blowing was complicated and could not be used for mass production. Later, a mold-blowing technique evolved where a glass blower would simply stick the end of the pipe holding the molten glass into a two-part ceramic mold. Not only could an artisan now blow a perfect vessel, but he could do it repeatedly using the same mold. The designs were usually carved into the mold in the negative so that they appeared in relief on the glass vessel. Many of these molds were intricately shaped. The blue cup above is mold-made, likely inexpensive, and possibly sold to tourists or to thirsty spectators in the Coliseum. The urn above is far more complex. It is much more difficult for an artisan to maintain control of a clearer color. He would have had to use different elements to counteract the natural blue-green hue resulting from the chemical composition of natron. Furthermore the handles were clearly cast on after the bowl was formed, demonstrating extra stages of work. You can see a demonstration of mold technique at https://www.khanacademy.org/partner-content/getty-museum/antiquities/ancient-glassmaking/v/glassmaking-technique-roman-mold-blown-glass
The Romans, ever the entrepreneurs, developed a thriving glass industry on an industrial scale, commercially producing and distributing glass objects widely throughout the Empire. The raw materials came from various parts of the Empire and glass items were produced in Rome as well as in production centers in Israel and the Levant and probably in Egypt. By 50 A.D., glass had become a cheap commodity in the Roman Empire because the mold-blown technique was far less labor-intensive than previous methods of production. Though little evidence exists of actual primary production sites, archaeologists know that large multi-ton blocks were being made in tank furnaces in the Near East and likely in Egypt using a process that took weeks. The final product was then broken into ingots and shipped throughout the empire. Interestingly, there is next to no archaeological evidence of Roman glass production sites in the region where Pliny wrote the Historia Naturalis at the time he wrote it. But evidence does exist at later time periods. Archaeologists believe that these later larger glassworks were merely built over earlier ones. In 1964, a huge block, originally perceived to be imperfect stone, was found in Bet She’arim, near the place where Pliny wrote. The nine-ton block looks like stone but its crystal structure reveals it to be glass that was apparently cooled too slowly. More recently, in 2016, archaeologists discovered the oldest glassmaking furnace dating from the late Roman period. It was found at Jalame, at the foot of Mount Carmel, Haifa, giving further support to Pliny’s assessment of the area. You can view a video of the site at http://www.ucl.ac.uk/archaeology/calendar/articles/2015-16-news/20160523
Despite the lack of evidence of primary production sites, a great deal of evidence exists of secondary production sites throughout the lands of the Roman Empire. These secondary production sites involved glass recycling where cullet (broken bits of glass) was collected in bulk and remelted into new slabs. These sites have been found from Slovenia to England, with an impressive example being discovered in London just two years ago. Many sites have also been found in Germany. It is now safe to assume that glass production could be found anywhere within the Roman Empire; Rome itself, however, had one of the most dynamic and flourishing glass industries. Roman artisans created a variety of objects and developed the first known glass windows. Because of the ubiquitous nature of the Roman glassmaking industry, glass items are some of the most abundant Roman artifacts found in the world today.
The glass industry didn’t completely disappear with the collapse of the Roman Empire. Because sites were scattered throughout the Empire, remnants of the industry continued to exist. Glassmaking continued to flourish in the Near and Middle East, in the Byzantine Empire, and later in the Islamic world. Due to the dispersal of technology, it even continued to evolve in Europe during the period following the fall of the Empire. The most significant technological development — the creation of wood-ash glass — occurred in Northern Europe and in the British Isles. This process uses ash from wood or bracken as the alkali component of glass instead of natron or other sodas. As a result, Europe could obtain the raw materials for glass production independently from the previous Near Eastern supply monopoly. Glass production did decline, however, because the wealth of the Roman Empire was not duplicated in the small kingdoms that arose after the Roman collapse. Nonetheless, fine examples of glass drinking horns from Germany and other parts of Europe survive today.
As the economies of the European kingdoms improved in the later Middle Ages, glassmaking advanced in Germany, Bohemia, Switzerland, and especially in Venice where cristallo glass flourished.
The first documented record of Venetian glass dates from 982 A.D. and names Dominicus Phiolarius as a master phial and bottle maker; but several centuries would pass before the Venetian monopoly developed. As the political and economic influence of Venice increased, so did its glassmaking importance. By 1291, glass factories were flourishing on the island of Murano, across the lagoon from Venice. The glassmaking industry was sent there to protect the Doge’s city from fires ignited by the furnaces. By the middle of the 15th century, Angelo Barovier was producing what was to become known as vetro cristallo or cristallo veneziano.
Cristallo was a pure, bright, completely transparent crystal glass which altered the design and appreciation of stem glassware, goblets, dishes, and bowls across Europe. The clarity of this glass brought its own magic; but it was its chemical makeup that allowed for light and elegant designs. Until that point, such elegance would have been nearly impossible to achieve with any regularity. Venetian glass making proved to be enduring and the fame of the Island of Murano and its glass makers continues until today.
The story of glass thus far concerns the evolution of decorative glass. The luxurious glass artifacts of antiquity were used mainly for jewelry and for religious and household items. They were the possessions of nobles, wealthy merchants, and clerics. During the Renaissance, new techniques of production enabled the use of glass to spread beyond the wealthy. The story of decorative and utilitarian glass continues through and beyond the Renaissance, but for our purposes, its relation to windows becomes more important to western architectural design and construction after the 12th century. I will begin to explore the architectural uses of glass, especially in relation to windows, in a future Construction Note.
Before we leave, it is worth remembering that the art of glass combines a magical substance, hovering mystically between liquid and solid, with the touch and the imagination of the artisans who shape it. It is, as Antonio Neri tells us, the “fruit of the art of fire,“ more “noble than any other metal.” But it is also the alchemy of the glassblower, whose power to transform these natural materials that is both mysterious and impressive. This mystery has captured poets, writers, and minstrels since the time of the Phoenicians. It captures us today as we watch the glass walls of Capitol Crossing climb to one hundred and twenty feet, to dazzle the eye and bring comfort to its inhabitants.
THE GLASS-BLOWER, by Jan Struther.
By the red furnace stands
Apollo mute,
Holding in upraised hands
His iron flute.
Slowly from back and brow
The bright sweat drips;
He sets the clarion now
Light to his lips,
And ever as he blows,
Without a sound,
His molten music flows,
Golden and round.
Wally Mlyniec
SOURCES
Thanks to archaeologist Michael Casimir Mlyniec for sharing his knowledge and his insights about early glassmaking and for his written contributions to this Construction Note. Thanks also to Bob Robidoux, Purchasing Director for Balfour Beatty Construction, for helping me understand some of the more technical aspects of underpinning pits and birdbaths. Finally, thanks to Abby Yochelson, my personal librarian who helps with research and edits all you read and all you will read from me.
Mary Elizabeth Brown, An Italian American Community of Faith — Holy Rosary in Washington D.C., Holy Rosary (2015)
Diane Dolbashian, Antonio Neri, L’Arte Vetraria, 1612, Corning Museum of Glass, http://www.cmog.org/article/antonio-neri-l-arte-vetraria-1612
Antonio Neri, L’Arte Vetraria (The Art of Glass) (1612)
Pliny the Elder, Historia Naturalis (ca 77 B.C.E.)
Rosemarie Trentinella, Department of Greek and Roman Art, The Metropolitan Museum of Art Heilbrunn Timeline of Art History, Roman Mold-Blown Glass, http://www.metmuseum.org/toah/hd/rmold/hd_rmold.htm
Anna Weller, The History of Venetian Glassmaking, http://www.bigbeadlittlebead.com/guides_and_information/history_of_venetian_glass.php
David Whitehouse, Glass, A Short History, Smithsonian Books (2012)
John Noble Wilford, Archaeologists Discover an Ancient Egyptian Glass Factory, New York Times, June 21, 2005, http://www.nytimes.com/2005/06/21/science/archaeologists-discover-an-ancient-egyptian-glass-factory.html
Jan Struther (Joyce Maxtone Graham), THE GLASS-BLOWER, The Glass-Blower and Other Poems, Harcourt Brace; 1st edition (1941)
Caren Yglesias, The Innovative Use of Materials in Architecture and Landscape Architecture, McFarland & Company (2014)
Chloe Zerwick, A Short History of Glass, The Corning Museum of Glass (1980)
Oxford English Dictionary, https://en.oxforddictionaries.com/definition/glass
Corning Museum of Glass, Glass of the Romans, http://www.cmog.org/article/glass-romans
Wikipedia, Department Store Tietz, https://translate.google.com/translate?hl=en&sl=de&u=https://de.wikipedia.org/wiki/Warenhaus_Tietz_(Heinrich-Heine-Allee)&prev=search
Wikipedia, Roman Glass, https://en.wikipedia.org/wiki/Roman_glass
Wikipedia, Oriel Chambers, https://en.wikipedia.org/wiki/Oriel_Chambers
Wikipedia, Natural History (Pliny), https://en.wikipedia.org/wiki/Natural_History_(Pliny)
University College London, Institute of Archaeology, Discovery of Key Roman Glass Making Furnaces, May, 23, 2016, http://www.ucl.ac.uk/archaeology/calendar/articles/2015-16-news/20160523
