Glycerol is a simple organic alcohol compound that is clear, colorless and viscous. Due to these properties it is used to calibrate a photometer to 100% transmittance which is the maximum amount of light that passes through a cuvette containing a sample and detected by a silicon photodetector. For honey and maple the calibration is done at a specific wavelength of light. The wavelength used is based on the appropriate method and represents a complementary color of the sample to be tested.