This guidance will help you to reglaze a window, refitting plain or leaded glass in a period house.
If the window is leaded glass, if you try to remove the glass, you will probably find that the outer lead, around the window, will have perished. It will therefore be fragile and you will have to replace it. Please read our advice on this.
When replacing a pane, wear thick gloves. Chip out the glass, and the putty. Paint stripper or household bleach can be used to soften the putty; apply it and then cover with clingfilm until the putty has softened.
Use pliers to remove the 'sprigs', the little nails holding the glass in.
Measure the opening, and subtract 3mm from the height and width. Try to get horticultural glass which has the imperfections similar to those of the original glass.
Getting the putty in requires a bit of a knack. Get a lump in your hand and work it until it has lost any oily sheen (it makes your skin beautifully soft!) and has formed a ball. Place it in the palm of your hand and using fingers and thumb force it out and into place in the frame. Then work forward, pushing it into place in the direction pointed at by your fingers/thumb – don’t drag back as this simply pulls it out.
Place the glass into the window and press all round it. Tap the sprigs into the wood; protect the glass from the hammer with a piece of thick card. Prepare more putty and press this around the edge. With a wet knife press the putty into place. Fill it proud; with the wet knife you can slice off the surplus.
Ideally do not paint the putty until one month has elapsed, overlapping onto the glass by 1mm or so. If painting has to be done quickly, wait till a skin has formed on the putty - several hours.