Turbidity is a reduction in the transparency of a substance caused by the presence of insoluble substances. This characteristic of the medium is not a clearly defined physical quantity, but refers to a clearly defined standard. For example, in the brewing industry, turbidity is measured in unit of EBU (English European Brewery Convention). The measurement of turbidity can be carried out by different methods: from historical (when the scale with letters of different sizes was put for a cuvette with a sample, the smallest letter that could still be read was a measure of the turbidity of the substance) to modern, more accurate methods, such as measuring of turbidity using three angle light scattering. : at 900 (to detect the presence of small particles), 250 (to detect large particles), and transmission 00 (to compensate the color of the sample). Turbidity analysis is used to determine the quality of products in various industries to check the efficiency of filtration processes.