The glass used in windows can help historians learn a lot about a building, especially in terms of its character, appearance and even its age. Modern glass is smooth and pretty much the same from window to window, older glass is not completely transparent and it tends to have a slight green hue visible as well as having a slightly rippled effect.
Very old glass was called cylinder, broad or muss glass and it was produced before 1674. It has a distorted and rippled effect and would often have air bubbles and other imperfections visible. Post 1674 we started to see crown glass being used which was blown into a bubble, pierced and spun. Once the glass was cooled it was cut into panes that could be used for windows. Whilst clearer than earlier types of glass it still had imperfections and a slight ripple in it.
In the 1830s plate glass became popular and the production of glass became industrialised. This reduced the cost of glass as well as increasing its quality, although there still remained a very slight distortion it was much improved compared to crown glass. This remained the most popular type of window glass until the early 1900’s when Belgian Emile Fourcault invented something called drawn glass, this further automated the process of making glass and it was pulled up over rollers into an area where the glass was cooled.
In 1959 we see float glass making an appearance which is still the technique used today. This process produces smooth, even and featureless glass, pretty much like your windows in your own home.
Whilst the methods used have steadily changed for the production of window glass, their style has been very much dictated by the architectural style of the period. This impacts the size, shape and number of windows seen in buildings of all types throughout the ages.
In today’s market, like many others we are overwhelmed with choice and so often one of the most important decisions to make with regards to choosing windows, is to ensure that they match both the exterior and interior of the property. We also have to consider security and noise pollution when making a final decision. Whether for a brand new office block or to replace existing windows in a 16th century cottage.