Years ago there was a product on the market (advertised in FineScale Modeler) called "glue zapper". It was made by the DMC company, Hammond, LA. A few drops on assembled plastic models (built with normal plastic cement like testors), and the pieces would pop apart. I had some and it worked on models over 20 years old. The company's phone number was long ago disconnected - does anyone out there know where I could find some, or if some other company is producing it?