Class A or Brush Grade Sealant - A thin viscosity (150-500 Poise) sealant designed for brush application. Most U.S. specifications designate this grade as Class A
(typically the thickness of cold chocolate syrup)
Class B or Extrusion Grade Sealant - Higher viscosity sealants (8,000-16,000 Poise), designed for application by extrusion via a pneumatic SemcoŽ gun. This grade usually is used for forming fillets and sealing on vertical surfaces where low slump/sag is required. Most specifications will designate these as Class B Sealants.
(typically the thickness of peanut butter)
Class C or Roller Grade Sealant - Medium viscosity sealant (1000-4000 Poise) designed for application by a roller or combed tooth spreader. This grade is most often specified for fay surface sealing. Often referred to as Class C, or Fay Surface sealants.
(typically the thickness of sour cream)