A method for monitoring a knock control and a device for knock control of an internal combustion engine are provided, in which digital knock data are obtained for the knock control in that the acquisition of data of a knock sensor, converted from analog to digital, is started at a start angle of the internal combustion engine and ended at an end angle. These methods comprise introducing a hydrogen peroxide-acetyl precursor solution to water, mixing, and then adding an aqueous source of a alkali metal or earth alkali metal hydroxide. By splitting the liner into two separate plates, a thermal break is provided between the two. In this way, color information color bands may be obtained without the need an infrared filter and infrared information is retained for use in other applications if desired.