The measurement of the turbidity of liquids can be carried out visually or by instrument, but visual methods can be subjective. This method measures instrumentally the scattering of light by the insoluble matter in a liquid and therefore gives an objective determination of turbidity. Turbidity in liquids is caused by the presence of undissolved matter (i.e. non-settling flocculation, gels or other suspended matter such as particles or droplets). In the case of finely dispersed undissolved matter, the turbidity may be determined by measuring the intensity of the light which is scattered by the particles when a beam of light is passed through the liquid. This International Standard specifies an instrumental method for determining the turbidity of clear liquids. It is applicable to resins and resin solutions, solvents, clear coating materials, monomers and any other liquids where clarity is specified.