The cementing is done with a brushable mixture of linseed oil, white spirit and whiting, with colour to make it black. This is brushed under the leads to seal the window. It also -with appropriate amounts of brushing - blackens the leads and solder to give a counterpoint to the glass.
It now needs to rest for a while. During this time it is important to continually clean the piece to avoid any cement "drips" or other movement of the cement while it cures.
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