Wet and dry film thickness

From the previous two posts, we saw how to calculate wet film thickness from the recommended spread rate. The relationship between wet film thickness and dry film thickness is dependant on a formulation parameter known as Volume Solids. This value, given as a percentage, is usually found on the Technical Data Sheet of the product. A Volume Solids of 40% means that when the paint dries
40% remains on the surface forming the dry paint film. So if the wet paint film thickness was 125 microns and the Volume Solids of the paint applied was 40%, then the dry film thickness will be 50 microns (125 x 40/100).
Two coats, applied at 8 square metres per litre, of a paint formulated at 40% Volume Solids, gives a dry film thickness of 100 microns.
Applying a product at the manufacturer's recommended spread rate ensures that the correct dry film thickness results and the performance of the coating is maximised. Thinning the coating by addition of water or solvent, or spreading the coating too far, only results in a thinner dry film - and the life expectancy of the system is reduced.