Windows

Glass was extremely expensive in the 1400 to 1600 era, and was not affordable for the vast majority of the common population. Windows were basically just openings in the building, with shutters or animal skin drapes. Timber mullions were set on diagonals to act as wind dampers to help keep strong draughts down. On higher-status houses stone surrounds were used, which may have had iron frame opening casements fitted later. The cross-sectional shape of mullions can be used to help date windows.

The repair of early glass is specialised work, and the care needed to undertake this type of work should not be underestimated in financial or project planning considerations. Breakage is highly probable, and the value of the glass can sometimes mean that frames have to be sacrificed. Also, there are many types of period glass within the categories of crown and cylinder glass. Modern replica glass is manufactured to mimic the appearance of period glass, but replication tends to defy mass production techniques and it may not be appropriate or aesthetically pleasing.

The decision when to undertake a full repair of a glazed unit is a question of balance. Cracks in small panes of glass may not affect the overall integrity of the window. If by repairing one small pane the remaining panes become vulnerable, this might not be an appropriate remedy. The economics of full repair may not become viable until several panes require attention. Conversely, if one or two panes of the window have been smashed, complete removal may be inevitable to save the remaining glass. Emergency boarding may have to remain over glass for some considerable time before appropriate work can be implemented, and the occupier's expectations concerning the speed of repair will need to be addressed.

The lead cames that hold small panes together are often attached to metal rods to reinforce them. If these become detached, the glass may become prone to bowing or breaking. The task of reconnecting the two components together is relatively straightforward and is a cost effective preventative measure. Small panes in lead cames are easier to repair, but it is still quite a delicate operation.

Replacing glass

The glass market was dominated by the skills of the French, Germans and Belgians. The main forms of manufactured glass were crown glass and flat cylinder glass. Crown glass was available throughout 1700s, cylinder glass from 1730s. Both forms were expensive for the day, and glass was not readily available in large sheets. Cylinder glass was by far the most common type.

If the glass is historically important, it may be necessary to remove glass from a frame and reuse it. Great care is needed for this task and it is best undertaken away from site. Even with the utmost care, panes can crack and allowance must be made for such eventualities.

It is often assumed that all historic windows were always glazed with crown glass. However, both crown glass and the cheaper cylinder glass were available. The glass tax influenced which type had prominence, and it is apparent that this balance was tilted in favour of cylinder glass when the tax was repealed in 1845, as the use of crown glass ceased almost immediately. British-made crown glass was commonly available from around 1680, with the more practical and lighter cylinder glass being introduced around 1730. Therefore a requirement to replace in crown glass can be reasonably challenged.