Later Improvements As the 18th Century progressed, the construction of sash windows improved. The most important development was that glazing bars became steadily thinner as the century progressed. Later in the 18th Century, larger panes of glass became available and the extremely elegant glazing bars, that we admire so much today, became general. In more expensive work, these bars were sometimes constructed of iron or brass, often painted to appear like wood.
Window construction improved also, and by the end of the 18th Century the basic construction, that is familiar today, has been developed. By the 1750′s sash pulleys in more expensive work were set into iron frames with a solid brass face-plate. The grooves in which the lower sash moved were not painted – a practice that went on to the 1830′s. It was a sensible idea, because the sashes would not jam or stick. In some areas the outer channel of the pulley style is still left unpainted.
Later in the Century, cast-iron and brass sash pulleys superseded the earlier types, and a multitude of other developments in sash-pulley design burgeoned throughout the 19th Century – illustrating the care, thought and invention, that went into the improvement of sash windows.
Although early sash windows were mainly constructed of oak, imported Baltic softwoods became widely used for sash windows. However oak and, later, mahogany, continued to be used up until recent times. In most work, oak was used for window sills, the rest of the window being constructed of soft wood, which remained the common practice from the mid-18th Century until the Second World War.
Among the numerous types of 18th Century sash windows, the tripartite or Venetian was an imposing example. It often consisted of a central sash with two side lights, one pane wide. The side lights were often fixed, with the sash cord running over their heads from the central sash into the weight boxes. A less common type was made so that all three sashes could operate, with wider mullions for the weight boxes.
Throughout the late 18th and early 19th Centuries, sash windows were used in the most complicated situations, often built to appear as casements in Gothic and Tudor Revivals. These revived designs often involved elaborate construction with moulded mullions and even concealed pulleys and weights.
In the early 19th Century, the use of margin lights became very popular and, combined with cast-iron balconies, created a delicate and extremely elegant feature now termed “Regency”, although this style continued into the 1840′s.
Throughout the ensuing three decades, sash windows was employed in Italinate villas and terraces springing up in fasionable areas, and in Victorian Gothic villas, with much plate-glass on the principal elevations.