Quick curing, 2 pound density foam used for flotation, insulating and filling. Must be mixed 1:1 equal parts. Foam expansion rate is approximately 25:1. Calculate the size of the cavity to be filled to determine the amount of foam needed.. Cavity Size Foam Required. 1 quart (57.75 cu. in.) 1.3 fl. oz.. 1 gallon (231 cu. in.) 5.2 fl. oz.. 7.48 gallons (1 cu. ft.) 38.2 fl. oz.