The precision of this test method is based on an interlaboratory study of ASTM C1519 - 04 Standard Practice for Evaluating Durability of Building Construction Sealants by Laboratory Accelerated Weathering Procedures, conducted in 2009. A total of three laboratories participated in this study, recording observations of the total loss of bond in adhesion and cohesion, cracking, crazing, chalking, and discoloration. Observations were recorded on a scale from 0-5, with 0 indicating no observed change, and 5 indicating excessive change. Observations on triplicate specimens of four different sealant materials (were made regularly every 4 weeks beginning with the 4 week weathering / movement cycle, continuing through the 48 week weathering / movement cycle, and then less frequently afterwards. One of the three participating laboratories stopped reporting all observations after Week 28, and another laboratory stopped reporting data after Week 32. Details of every rating reported in this study can be found in ASTM Research Report No. C24-1057.