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Glazing compound

Also called putty, glazing putty

The putty that beds a pane in its rabbet and seals it against the weather.

Glazing compound is a soft putty, traditionally whiting and linseed oil. A thin layer goes into the rabbet first, and the pane is pressed into it. That layer is the bedding, or back putty. More putty is then tooled to a neat bevel across the front, from the glass to the edge of the rabbet.

The putty forms a skin and is painted, with the paint lapped a little onto the glass to keep water out of the joint. It hardens and cracks with age, and replacing it is the main upkeep of an old window.

The putty seals but does not hold. Small metal points driven into a wood sash, or spring clips in a steel one, keep the glass in place.

Bottom rail of a steel sash in section, outside at left

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Steel sash, bottom rail in section
Bottom rail of a wood sash in section, outside at left

Hover or tap a part to see what it is called.

Wood sash, bottom rail in section

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