The Heritage Directory

                                                                                                                                 The Heritage Directory has provided the following articles as an informative guide to aspects of the historic environment. The articles are grouped into the following areas : General & Legal, Architectural History, Interiors, Exteriors, Gardens, Preventative and Remedial and Professionals and Contractors.  


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Glass in Historic Windows

 

reflection in historic glass

Old glass should be retained where possible in historic windows as it adds considerably to the character and history of a building. Where a window has to be completely replaced, the historic glass should be reused and any shortfall made up from new crown or cylinder glass. Modern float glass is flat and mirror like, and lacks the  bubbles, impurities and  textures which gives old glass its character. 

Cylinder Glass ( Muff Glass) 

The earliest type of glass in England was broad glass, which developed into cylinder glass, which was relatively crude. This was made by blowing a  cylinder of glass, cutting it and flattening it out. It was popular until the 18th century. In 1834 the Chance Brothers improved the production of  cylinder glass, which reduce cost and increased sheet size. Tax on glass was removed in 1845 and the  larger sheets resulted in the reduction of the number of panes in sash windows.

Crown Glass 

A superior form of glass, crown glass was successfully produced in England from 1679, having previously been known as Normandy glass. The cost was double that of cylinder glass but by the l8th Century most window glass was crown. The glass was spun out producing a circular plate but produced panes of glass of limited size and therefore windows were divided by glazing bars. 

crown glass fanlight

A crown glass fanlight showing the reams or waves from the glass being spun out.

Plate Glass 

In the 17th century production of plate glass was begun in England but was limited generally to mirrors. Its cost was 6 times the price of other glass in 1734 as it had to be laboriously polished. The most famous example of this expensive glass is the central window at Hampton Court. From 1845, cheap cast plate became popular with the removal of taxes and import of French plate glass. 

20th Century Glass 

The 20th century saw a number of innovations such as rolled plate, machine cylinder, polished plate and flat drawn sheet glass, of which horticultural glass is a variation. In 1959 Pilkington invented float glass with its smooth finish which is the most common form of glass today.

This is a living document, in the sense that it will be updated and added to over time.

All information on this website is for information purposes only. It does not constitute formal, legal or other professional advice and the Directory should not be relied upon as an alternative to formal advice.