The Pajama Factory Windows

As a photographer, I spend a lot of time looking at different types of light and shadows, so when I found the Pajama Factory in Williamsport, PA, I was attracted to the exceptional quality of the light afforded by the factory’s large windows.

What I didn’t know was how carefully engineered a modern factory of this era was. Manufacturing was coming into full swing with modern methods on a scale that had never been seen before. Where old factories were smaller, darker and less pleasant for workers, factory owners were learning that productivity could be improved significantly by designing workspaces that employed what would one day become known as ergonomics, a term not coined until 1949, a full thirty years after the Pajama Factory was completed.

An important consideration in designing a large work area is, of course, that sufficient light be made available to workers. Electric light was a fairly new thing, but it was expensive and inefficient for the kinds of spaces that needed to be illuminated. Architects found that they could efficiently light large spaces through the use of carefully-engineered window systems. The engineers needed to add as much light as possible and of course, more windows mean more light.

A typical factory built in the late Nineteenth Century was made of brick and timber, with wood-framed windows that were of course much smaller and less-efficient than they now needed to maximize the usefulness of the spaces they wanted.



Around the turn of the Twentieth Century, architects started designing steel framed factory structures with steel-framed windows that would allow for vast, multistory buildings, such as the 300,000 or so square feet of the Pajama Factory. They designed their buildings to have greater and greater percentages of their outer surface covered with windows and these new techniques allowed them to reach better than eighty percent coverage with glass. This required new types of framing for the windows, such as the “Detroit Fenestra” designs that the Pajama Factory has so many of. These were incredibly strong, far stronger than could be made of wood, and far easier to maintain. Double-glazed windows were an option, but often decided against because the cost of heating the factories was said to be “practically nil.” (Sadly, this is no longer true…)

So by the time the newer buildings of the Pajama Factory were built in the years before and just after World War I, architects could design a building as large as they could afford, with glass covering nearly all of the outside. The problem was, if they used regular flat window glass, most of the light would fall right near the window sills, blinding and baking the workers situated there, while the workers towards the center were left in relative darkness. Lighting engineers of the day set about to tackle this problem. Frosted or ground glass, where the shiny surface was sandblasted to make it translucent, simply reduced the amount of light that passed through. This helped near the windows, but the centers of the rooms on the factory floor were still in shadow. It became clear that the answer to the problem was textured glass of some sort. Glass with patterns of raised bumps were tried. They were an improvement, but not good enough. “Maze glass” had a raised pattern molded to the surface and this had excellent dispersion qualities, but not enough reach towards the center of the halls.

The highest efficiency was found using a type known as “prism dispersion” glass. This type is molded to have an interior surface of 90º ridges about 1/32nd of an inch wide, running parallel across the glass’ surface. These “prisms” caught and redirected the light towards the center of the room, creating a pleasant and efficient environment in the center of a building even sixty feet wide. (A bit more space could be added as a center hallway area, as that didn’t need to be as well-lit.)

Factories could now be built as large as they could be lit. This led to the type of structures exemplified by the Pajama Factory—long, long buildings with windows situated to the West and East.

Looking at the windows of the factory, you’l notice that this kind of glass was only used on the upper panes in each sash. There were a few reasons for this decision: one factor was cost—prism dispersion glass was far more expensive than the smooth kind. It also worked best in the upper part of the room, above the workers and their machines and in combination with white-painted ceilings and columns. Lastly, it was found that the workers actually needed to occasionally glance at a distant object outside, to reduce eye strain. This was balanced against the concern by factory owners that workers, “especially women” would spend too much time staring out the windows rather than working. (This was, after all, 1916 in the example I found and people actually said things like that in public.)

After the windows were in place, the machinery had to be laid out in a manner that didn’t interfere with the light dispersion. Long rows of work area were arranged almost perpendicular to the line of windows so the light could efficiently flow. Ideally, workers would not be facing the windows directly, as this caused undue eye strain, as well as distraction. The same publication noted that this technique had been employed for many years in keeping horses in stables, again stated with no implied irony.

It’s interesting to learn how and why these buildings were made the way they were and what a state-of-the-art facility it was. It’s exactly these sorts of details that make the building so appealing for artists and craftsmen even today, so much more so than even a new building.

Almost a hundred years later, many of the original prism dispersion windows remain, though a few have been lost to the ravages of time. Where practical, broken panes have been replaced with matching vintage panes sourced from salvage dealers.

The next time you visit the Pajama Factory, take a look at the windows and enjoy our exceptional light.