To produce accurate replicas of intra- and extraoral tissues, the impression materials should be:Sufficiently fluid to adapt to the oral tissues. Viscous enough to be contained in a tray. Able to transform (set) into a rubbery or rigid solid in the mouth in a reasonable time (less than 7 min).  Resistant to distortion or tearing when removed from the mouth. Dimensionally stable long enough to allow one or more casts to be poured.  Biocompatible.  Cost-effective in terms of time as well as the expense of the associated processing equipment.Key Concept: The impression material should be resistant to distortion or tearing when removed from the mouth. Reference: Phillips’ science of dental materials / Kenneth J. Anusavice, Chiayi Shen, H. Ralph Rawls.—12th ed.Page no 152