An apparatus and a method are disclosed for performing a light-absorption measurement of a specified amount of sample. A method for performing a light-absorption measurement of a specified amount of sample includes placing the sample on the surface of an apparatus including the surface and a light reflector, the light reflector being mechanically coupled with the surface and separated from the surface by a separation distance, changing the separation distance, while the light reflector remains mechanically coupled with the surface, to a first separation distance, and performing a first light-absorption measurement of the sample via the apparatus, while the separation distance is equal to the first separation distance, and while the sample is subject to pressure force.