Solvents, Diluents,
& Thinners

THINNING OF PAINTS

Q:  When a coating chemist formulates a coating and recommends up to "25% reduction by water" how exactly must the coating be thinned?

A: Someone with a chemistry or science degree would probably interpret this to mean that you take 0.75 gallons of the paint and add 0.25 gallons of water to make up a full gallon.

Painters, on the other hand are not familiar with this principle and will generally start with a one gallon can of paint and add one quart (0.25 gallons) of water to make up a total of 1.25 gallons of paint.  When calculating the VOC content of the mixed coating the two approaches lead to two very different answers.   Therefore, if you know of painters who are given thinning instructions in terms of percentage additions, it would behoove you to find out exactly how the instructions are being interpreted so that your VOC calculations are correct.

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