Repair a leaking leadlight window
Leadlight windows are more mobile than full glass panes and can often develop a leak if the putty seal cracks out. They are easy to fix.
Before starting, look carefully at the window to understand how it is constructed. Leadlights are made using H-shaped lead cames which, in
cross-section, look like this.
Each glass section has been cut to shape, then the lead pieces fitted along the
edges (see the two photos below). The corners, where lead meets lead, have been soldered. Finally the whole leadlight window has been puttied using whiting, black oxide, linseed oil and turps.
The easiest way to do repairs to a leadlight is to take the window off its
hinges and work on it in a horizontal position. If this is not possible, choose
a dry day to do your repairs.
For repairs to an established window, buy only a small amount of whiting (fine grade calcium carbonate powder, sometimes called chalk dust). 1 kg will be ample. This can be purchased from hardware stores or glass suppliers. Buy, also, the smallest quantity possible of black oxide. The oxide will turn your putty
dark grey. Without oxide the putty will turn out a beige colour, so check the
window you are about to repair to determine which colour you need.
If you want dark grey or black putty, halve the whiting into two containers.
Into one container of whiting add a heaped teaspoon of black oxide and mix them
together. This container now represents your dry putty powder. If you are wanting beige putty you do not need to halve the whiting.
Make up a small bottle of one part raw linseed oil and one part mineral turpentine.
Spoon a couple of tablespoons of putty powder (whiting or whiting with oxide)
into a container. Make a well in the centre and pour in a little of the oil/turps mix. Stir together. You are aiming for a consistency of peanut butter. If the mix is too dry, add a little more liquid. If it is too wet, add more dry powder.
Check the window for any areas that might be devoid of putty or not filled
properly. Horizontals will often hold water that has run down the window and
gradually develop leaks. The top edges and inside edges of diamond shapes are
also prone to develop leaks over time. If you need to work on an area around
stippled or rough glass, apply masking tape along the edges of the glass, next
to the lead, so putty does not lodge in the stipples or rough areas. (Usually
the smooth side of rough glass faces the exterior of the building.)
Force the putty into any gaps between the glass and lead with your finger. Make your way right round the window into areas that need it (photo below).
Now use a soft toothbrush to apply whiting along the edges of the came, to clean
up the glass.
Take care not to scrape out the putty you have just applied (see below left).
This has a dual purpose of drying the putty out a little on the edge of the came
and cleaning the glass. Whiting can be applied more readily to a horizontal
surface (below right).
Once you have cleaned all the edges, apply more whiting to the glass panels with a soft hearth brush, cleaning with circular motion. This can be a dusty process, so wear a dust mask.
The whiting will soak up the oil and leave the glass clean. It will also help clean any putty on the lead cames. Be vigilant as you do this process because dried putty will be very hard to clean off at a later date. Applying whiting to the painted window frame with the toothbrush will also help clean up.
Now, using a small blade flat screwdriver or a nail, pick out any extra putty that might be lodged in the corners of the glass sections. Apply more whiting if necessary to do a final clean, and pick it out of the corners too. Your window should now look complete and clean.
If you have been working with the leadlight in situ, don't forget to clean up the window sill ..... and the plants underneath, or you will not be popular with the head gardener! Brush the whiting away and clean up with water.