Plastic - Clot Activator - Chemistry, Serology, Immunology, Blood Bank - Routine blood donor screening, diagnostic testing for ID - Invert 4-5 times - 60 mns to clot. Chemistry - SST (Serum Separator Tube) - Serum specimens for diagnostic testing for ID, routine testing - Inver 6-8 times - 30 mns to clot. 5. Green, Light Green, Green/Gray. Chemistry - NaH or LiH - Used for STAT chemistry order - plasma testing in chemistry - invert 6-8 times.