Consolidation of degrading craft foam

I have an interesting case of some very old Television stop motion models suffering from a bad case of foam degradation and need to find a way to seal/consolidate it. It is craft foam but many decades old and seriously degrading.  A slight knock to the plinth they are attached to will dislodge chunks of it.

Initially I plan to very carefully clean off the loose parts and the dust but long term, they need stabilising.

I know there are products on the market that can do this but am totally unaware as to how they may affect them chemically over time.

Although stuck to the plinth, the figures are still movable and their hands are a soft putty like substance but they hold their shape.

Any or all advise would be gratefully received.

Rachel Davis

BBC Archives Conservator