Products and spraying
Thinning ratio: thinner volume and volume solids after thinning
- where
- thinner to add (L)
- paint to be thinned (L)
- parts of thinner in the ratio
- parts of paint in the ratio
- thinner as a percentage of the paint (%)
- volume of thinned paint (L)
- volume solids after thinning (%)
- volume solids as supplied (%)
Explain this equation
Converts a data sheet thinning ratio such as 1 part water to 10 parts paint into the litres of thinner to add to your tin, and shows how far it dilutes the solids.
V is the paint you are thinning. p and q are the two numbers in the ratio, thinner first and paint second. Vt is the thinner to add, th the same thing as a percentage, Vm the total mix and VSt the volume solids left in it.
The thinner scales directly with the paint: p parts for every q parts of paint. The solids line spreads the original solids over 100 + th parts of mix instead of 100.
Sense check: 10 litres at 1:10 needs 1 litre of water, making 11 litres, and a 49% solids paint drops to about 44.5%. At 1:5 the thinning is 20%.
Watch out: keep the ratio the right way round and the same for every batch on a wall, or sheen and colour will differ.
Turns a data sheet thinning ratio such as "1 part water to 10 parts paint" into litres, and shows how much it dilutes the solids.
Enter your values to see the result.
Good to know
Dulux Trade data sheets give typical limits: Diamond Matt up to 1 part water to 10 parts paint for sealing new surfaces or for airless; Weathershield Smooth up to 1:10 for normal use and 1:5 for airless or sealing. Use the same ratio throughout a wall so cut-in and rolled areas match. The thinned solids figure feeds the wet film calculator: thinned paint must go on wetter to give the same dry film.
Common mistake
Mixing the ratio the wrong way round (1 part paint to 10 parts water) or measuring by eye from a full tin, so successive batches differ in sheen and colour.
Limits
Volumes assumed to add; thinner assumed fully volatile. Never exceed the data sheet's maximum thinning, and only use the thinner it names.
Sources
- Dulux Trade Diamond Matt product data sheet (volume solids 49% white; minimum application temperature 8 °C per BS 6150; recoat 4–6 h; VOC max 1 g/L against 30 g/L limit, cat. A/a; thin up to 1 part water to 10 parts paint)
- Dulux Trade Weathershield Smooth Masonry Paint data sheet (volume solids 38% white; do not apply below 7 °C or above 80% RH; recoat 2–4 h; VOC max 10 g/L against 40 g/L limit, cat. A/c; airless thinning up to 1 part water to 5 parts paint)
- Hempel technical guideline: Mixing and thinning (volume solids after thinning = VS × 100 / (100 + % thinner); worked example 56% VS, 15% thinner, 75 µm DFT)
Results are calculations from the published methods and figures shown, and depend on the data you enter. Coverage depends on the product, surface and application. Always follow the paint and wallcovering manufacturers’ data sheets and BS 6150 / BS 8000-12. Check prices and VAT with your own records and HMRC.