In principle, the color of an oil is not an absolute quality characteristic. After all, almost any desired shade can be produced with the smallest quantities (less than 1 liter of pre-dissolved dye per 20,000 liters of oil) of the corresponding coloring agent. From pink to bilious green - almost anything is possible. Depending on the intended use, the consumer also expects a certain color shade. Golden yellow for transmission and hydraulic oils, red for ATFs, oils for medical equipment or food processing machinery should be as light as possible. Oils in air filters, on the other hand, are often colored blue.
In the case of an uncolored oil, the coloration depends on the origin, i.e. the well, the degree of refining and the intensity of bleaching of the base oil. However, due to the addition of additives, which in higher concentrations can look up to black, even water-light base oils often become considerably darker.
Nevertheless, the change in color of an oil filling can also provide important information about aging, e.g. oxidation, or about any impurities in an oil. Or quite simply: if the color of a sample deviates from that of the previous sample in the trend, there may be incorrect filling or overheating.
For certain oils, the assignment of a color number is done by a laboratory technician. The color impressions must be basically comparable, i.e. what is light for one laboratory technician may not be evaluated as dark by the other. The oil is classified with the foils of a color chart according to ASTM or DIN ISO, compared and classified into one of the eight color numbers. The color intensity is marked as "color" according to DIN ISO 2049. For support, dyed plastic filter templates are compared with the oil to be analyzed, decanted into a 15 mm thick cuvette. If the color impression between a filter and the oil in the cuvette appears to match, the oil is assigned the corresponding color number by the observer. However, this method of classification depends on the subjective impressions of the observer and often also on the surrounding light conditions.
In order to obtain a clear and comparable color number quickly and without having to decant the oil into a cuvette, OELCHECK is breaking new ground with the WaveCheck 300.
The color number measuring instrument was specially developed for determining the color numbers of oils. In close cooperation between the Institut für Mikrotechnik Mainz GmbH (IMM) and OELCHECK, the instrument was designed for the typical geometry of used oil analysis sample bottles with a standard diameter of 40±1 mm. The sample bottle is placed in the WaveCheck as it is delivered. After approx. 5 s, the color number can be read off or transferred to the database. The blank value for the empty plastic bottle is taken into account in the determination. It is no longer necessary to decant the oil into a cuvette or to clean or dispose of the cuvettes. Time and costs are reduced accordingly. The color number is determined with reproducible accuracy in steps of 0.5 according to DIN ISO 2049.