It's a solvent called Xylene. It's used to make acrylic sealer, to dilute it, re-emulisfy it and clean it off.
Your seal supplier should be able to supply it, they will call it xylene, thinners or solvent
The exeption to this is of course resiblock (superior I think) as thats polyurathane and cant be cleaned off/re-emulsified with solvent