Window Moulds

The sash and case window design dates back to the late 16th Century. The oldest examples still standing in Britain are in Ham House in London, dated 1670.

The sash window became increasingly popular in Georgian and Victorian properties. 

Original sash and case windows were small in size and glazed with blown Crown glass, this style of glass was hand blown and extremely expensive and timely to manufacture. As such, sash and case windows were designed with more timber and much smaller glass panes in a 6 over 6 or 8 over 8 astragal design.

Original astragals started off quite thick, around 35mm with small panes of crown glass. When the Window Tax of 1696 was introduced sash and case windows gradually became larger in size to cut down on the number of windows in the property. This led the timber astragals becoming increasingly thinner, around 16mm, to allow more glass and light into the more popular Georgian style of properties being built across Britain. Eventually, the Glass Tax of 1746 was introduced which taxed a property based on the number of panes.

The introduction of Plate glass manufacturing during the 1770s made glass a lot cheaper and quicker to produce. As a result of this, we saw a decline in sash windows with astragals, many were simply cut out the original sash, to make way for large single-pane windows.

The removal of The Window and Glass Tax of 1696 ended in 1845 which led to a revival of astragals in sash windows.

The glass wasn’t the only component of a sash window which led to their development. Architects began to experiment with astragal design, horns and window moulds.

From the early 1600s through to the early Victorian era there was perhaps only a handful of Joinery manufacturers in each city and possibly only one or two in smaller towns. Therefore, many of the sash and case windows were manufactured by the same companies. Windows which were built during a specific period in history contain the same window mould, as cutters were very expensive and often reused.

In Edinburgh for example, there is an Old Town mould, New Town mould, Lambs Tongue and Ovolo. These moulds represent different areas of the City, built during different periods throughout history.

In some cases, an Architect would request a bespoke mould to be commissioned for the windows of a grand property.

Hermitage Windows will always retain the original window mould of a property when manufacturing new sashes. If we can’t find one in our extensive archive, our workshop craftsmen will take detailed dimensions and templates and run our own cutters.

The preservation of fine details within historic buildings is something that Hermitage Windows takes great pride in and sits at the heart of our company.