Copydex in the UK is an off-white rubber based glue.  It does not
change colour with stirring, and merely becomes translucent after
setting.

For small components, (e.g. thin speaking pneumatics) application
to the wood only is usually sufficient, followed by immediate mating.
For larger items, (e.g. heavy bellows cloth), fairly generous appli-
cation to the cloth as well as normal application to the wood, with
a slight delay before matching, seems to give good airtight results.
Hot weather reduces the glue's thinness and working time considerably,
and only small amounts of glue should be poured out for use.

Roger Waring
The Pianola Workshop
Solihull
England