Lead Repair and Replacement

 

Copyright © 1996-2012  Geoffrey Wallace Stained Glass

 

The lead matrix that holds all of the separate pieces of glass together is actually very weak but it is just this soft, malleable quality of the metal that protects the glass panes and allows windows such longevity.  The lead works in harmony with the much more rigid leadlight cement, that is worked under the flanges of the lead calme and around the edges of each pane of glass, to form a framework that is both supportive and forgiving.  The lead works as a fail safe component that will distort, buckle. bend or split hopefully before any damage is done to the glass.

The two examples to the left are the result of building movement which has caused the window opening to spread, stretching the stained glass panel as a result.  As the window was originally set in hard, unforgiving portland cement mortar, the panel was unable to pop free of the glazing channel which caused localised stretching and splitting of the fabric.  The main body of the window though is still quite sound and solid.

Stretching of the lead calme

Splitting of the panel.

Most damage to the lead structure of a window is very localised and rarely requires the invasive and expensive total re-leading of the window.  More often just the damaged sections will require repair or replacement  This is also true for buckling or bulging panels because the malleable lead calme can be carefully straightened back to its original flat plane without necessarily replacing any of the original lead calme.

An exception to this rule occurs with lead that was produced in Australia from the mid 1950s up to the early 1970s.  The lead at this time was highly refined almost ‘pure’ lead which has proven to lack the resilience of the older lead alloys which contained trace elements of other metals such as copper, tin and silver.  The failed lead calme below dates from 1970 whereas the window above dates from 1887 with lead remaining in excellent condition.  `                                                                                                                                           

Failed ‘pure’ lead from 1970.