What is the difference between weight and volume solids of my roof coating?
Weight solids is a measure of the “weight percent” of the roof coating in the can. It is an arithmetic computation, of a simple laboratory test, where a sample of the coating is accurately weighed and placed in an oven and the solvent (water or organic solvent) is allowed to evaporate. The sample is reweighed. The weight of the dried sample is divided by the weight of the wet sample and described as a percentage. Hence if a 10.0 gram sample of wet coating is dried in an oven and reweighed if the dry weight is 5.0 grams, the coating is 50% weight solids. This provides some indicator about the amount of quality in the can. Since coatings are purchased by volume ($/gallon), and since water is very cheap, it can be possible to charge a low price for a coating merely by adding water. The specification for weight solids will aid the purchaser in determining how much value there is in the can.
