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What’s in a window? Probably muntins if you’re in Kentlands

How Crown and Cylinder glass manufacture shaped Kentlands

Those of us who live in modern industrialized nations tend to think of glass covered windows as a normal part of our home but this is a relatively recent development. The earliest houses had few openings and those only provided essential functions such as an entryway or an outlet for the smoke from a fire. Other gaps in walls or roofs were non-existent in colder climates and limited in moderate ones.

Ancient windows began as simple openings. As civilization progressed they acquired movable or removable covers. These covers were first made of materials similar to those used for the wall or roof but evolved to others, including translucent membranes such as vellum, to allow some light to pass through.

Glass windows came much later.

Glass is an unusual material in that it occurs naturally — the volcanic glass obsidian, for example; as an accidental by-product of human activity — such as smelting metals like copper, tin and lead; and through intentional production. Humans developed the technology to make glass in Mesopotamia about 1500 Before the Common Era (BCE). Early glass manufacturing consisted of two steps: making the glass ingot, which was a high-value trade good; and making final products such as beads, decorative objects and small containers from it.

The technology needed to make clear glass was developed by the Romans in Roman Egypt around the year 100 of the Common Era (CE). Small, thick glass windows began to appear but they had very poor optical properties because they were effectively blown glass jars that had been flattened out.

The first manufacture of plate glass appears to date to approximately 1620 CE. While a variety of techniques were developed, two appear to have dominated plate glass production until the industrial age: Crown Glass and Cylinder Glass.

Crown Glass combined glass blowing with spinning the hot glass on a punty so that centrifugal forces would transform the initial blob of glass into a circular plate with a central lump or “crown.”  The resulting disks could be up to six feet in diameter and combined good optical properties with a variety of imperfections. These defects included differing thickness across the disk with the thinnest glass at the edge and a large imperfection, called the crown or “bullseye” at the center.

Cylinder Glass was produced using glass blowing techniques. First, a quantity of softened glass would be blown into an empty glass sausage shape, often using a pit for maximum length. Next, the two ends of the sausage would be removed to create a hollow cylinder, the cylinder cut lengthwise, and the glass reheated so that it could relax into a relatively large flat sheet.

Manual production made Crown and Cylinder glass expensive, limited its size, made each finished piece unique and resulted in a variety of imperfections. These limitations, and the round Crown Glass disk, led people to cut the glass into smaller but carefully laid out shapes to build larger windows using lead to join separate complex shapes or muntins to hold square, rectangular or even diamond-shaped ones. It also allowed using the more valuable glass with few imperfections in high-value items and the panes or lights with poor optical qualities in lower value ones such as windows that distorted one’s view.

The industrial revolution revolutionized glass manufacture but much of the glass for windows was still produced by manual techniques well into the Nineteenth Century so muntins were common in the windows in homes built before, approximately 1850 in the areas such as Georgetown and Old Town Alexandria.

According to the Washington Post, “[Andres] Duany and [Elizabeth] Plater-Zyberk advocated neotraditional planning — a precursor to New Urbanism — based on functionally and aesthetically viable physical patterns derived from 18th- and 19th-century European and American urban settlements such as Savannah, Charleston, Alexandria and Georgetown.

According to Mike Watkins, Kentlands’ original Community Architect, Kentlands’ early designers and builders were free to choose house designs because that freedom was an underlying principle of the original Kentlands code, c.a., 1990. They often chose architectural styles – Federal and Queen Anne for example – as their inspiration, historicist designs that fit Kentlands’ streets and alleys and were in keeping with the nearby historical neighborhoods. These early builders were the ones who decided to include muntins in many, but not all, of Kentlands’ house designs as a tour of the neighborhood clearly shows. For example, the Kentlands Mansion does not have muntins.

Muntins are, however, one of the common design features that gives our neighborhood its consistent, and “established” appearance so they were added to the Kentlands Code during a revision that took place after Watkins stepped down as Community Architect and are now required for new and replacement windows.

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