Coating manufacturers in Europe and the United States attach great importance to the volume solids of coatings rather than mass solids. Volume solids can determine a series of construction parameters and commercial data of engineering quotations, such as wet film, dry film, theoretical spreading rate, coating sting, unit price per square meter, etc.
Coating volume solids are defined as the volume ratio of the non-volatile components in the coating to the liquid coating. Traditionally, this data is calculated according to the paint formulation, but because other factors, such as the shape of the pigment, residual solvent or shrinkage of the paint film, are not considered, the calculated value is quite different from the actual value. In addition, for different types of coatings, the effects of these factors are also correspondingly different. The volume solid content listed in the product description is measured under laboratory conditions according to ISO 3233 or ASTM D 2697 method, and the value measured by this method is usually slightly higher than the theoretically calculated value.
Most paint manufacturers use a very practical method to estimate the volume solids of a paint. This method is to measure the thickness of the paint film before and after drying, and calculate the volume solids according to the following formula:
