Page 23 - Curriculum Visions Dynamic Book

corrosion: the slow decay of a substance resulting from contact with gases and liquids in the environment. The term is often applied to metals.
 Lead was a common
roofing material for grand buildings because it could readily be moulded into shape. Beginning with St Sofia in Instanbul, the fashion for leaded domes spread across Europe. This picture is of Venice.
Lead is used more sparingly on modern buildings, but it
still has an important function as lead flashing. The soft lead sheet is let into the brick courses and then laid out and moulded over the top edge of a window. This provides an easily laid, long- lasting and waterproof seal for the top of the window.
Leaded glass
In the past it was only possible
to make small panes of glass.
As a result, some means of joining them together had to be found. This is why many old windows were made of panes of glass held together with strips of lead.
Lead is soft and was easily moulded around the panes.
Lead also melts at temperatures far below that of glass and so could be melted to run into the window frames and seal the glass.
(Modern frames use diamond leading which is simply stuck on to the outside of the pane for decoration. It serves no other purpose.)
 Traditional diamond leaded windows as used in the original Maryland State House complex, Maryland, USA.
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