[Arran]

Reforming an electrolytic filter capacitor, inside a sealed aluminum can, may or may not work depending on how old they are. I have encountered some "dry" electrolytics, in the twist lock style cans, in sets from the early 40s that were still functional, but I would not trust them, the 1960s maybe. If they are the cardboard cased ones, that look like a toilet roll, with a wax plug in the end, no, those are garbage, they were only meant to last about 5 years from new, the only thing they are good for is a tube for restuffing purposes.
Regards
Arran