Most common form of disinfection of alginate impression material is
Spraying 1% sodium hypochlorite
Spraying 5% sodium hypochlorite
Immersing in 1% sodium hypochlorite
Immersing in 5% sodium hypochlorite
The  current  protocol  for  disinfecting  hydrocolloid impressions recommended by the Centers for Disease Control and Prevention is to use household bleach (1-to-10 dilution), iodophors, or synthetic phenols as disinfectants. 
Guide for selection of Appropriate Disinfection Method for Impressions Transported to a Dental Laboratory