In article ,
"The Medway Handyman" wrote:

Bought a can of Polycell expanding foam for a job the other day - £7 odd in
Focus. Used a small amount. Wanted to use it again over the weekend and
everything is gummed up solid.

I have found (over a couple of years, with more than one can) that the
trick is to wait for everything to solidify, then use appropriate tools
to pick, scrape, push out the solidified foam. I use an old hat pin (!!
dunno where we got it) to push the core out of the main application
nozzle. Because of the smooth surfaces of the applicator there's never
much of a problem in cleaning off solidified foam.

The wife's nail varnish remover is used for cleaning stuff that's still
gunky.

john