I have three hutches with broken stoppers inside. (just the disc and rubber) What can I safely use to dissolve the gasket enough to get the whole thing out? PB Blaster? Acid?
VM&P Naptha (lighter fluid) usually dissolves rubber fairly easily. Acid would be a no-no if you want to save the wire bail, and it still probably won't affect the rubber.
Not sure how long it would take to actually dissolve the rubber, but if you can position the bottle so that the gasket is soaking in the naptha, or just fill the bottle if you have enough, it should soften the gasket enough so that you can just pull it out of the bottle. You can buy naptha by the gallon at most hardware/home improvement stores.