The mechanical behavior of a one-part, chemically-curing silicone sealant is defined by its primary variables: stress; strain; time; and temperature; using a model specimen. The material proved to be temperature independent in the region important for sealants, with some deviation from the rule near the crystallization temperature under high strain. The remaining three variables describe behavior in a three-dimensional co-ordinate system. Projection of the break points in the logarithm of strain vs logarithm of time plane is the link between laboratory testing and outdoor performance. By extrapolating the regression line of the break points to six months, extensibility of the material can be predicted. A testing procedure suitable for standards is proposed that links laboratory testing with outdoor performance. -- CCI