What is solids content?
Solids content is the proportion of solid matter that remains in a liquid building product after the solvent or water has evaporated. It is expressed as volume per cent (vol%) or weight per cent (wt%) and is a key indicator of the quality and coverage of paints, lacquers, adhesives and coatings.
How is it measured?
Solids content is determined in the laboratory by drying a measured amount of product to constant weight. What remains is the dry matter: binder, pigment and any fillers. The difference between wet and dry weight is the evaporated fraction.
The higher the solids content, the more material is left on the surface after drying. This generally means a thicker dry film per coat and therefore better coverage and protection.
Application
- Paint and lacquer — determines the dry film thickness and the consumption per square metre
- Coatings — used to calculate corrosion or wear protection
- Adhesives and sealants — indicates final strength and shrinkage on drying
- Bitumen and roofing — determines the final film thickness on the roof
- Mortars and thin-bed finishes — affects adhesion of thin layers
Points of attention
- Volume solids are usually more meaningful than weight solids for calculating dry film thickness
- Water-based paints often have lower solids content than solvent-based ones
- High solids content does not automatically mean better paint — the composition of the solids matters
- Thinning reduces the solids content; over-thinning leads to insufficient coverage
Related terms
- Binder
- Bitumen
- Coating
- Acrylic
- Conserving
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