Disclosed are a tool and method for identifying the relative strength of subsurface intervals through which a borehole has been drilled. The second tube portion communicates with the first tube portion through the main body. The method includes preparing an aqueous solution containing one or more polymer; and introducing the aqueous solution as droplets into a solvent capable of dissolving water by 1 mass % or more and less than 50 mass % to form the polymer into dispersed particles in the mixture of the aqueous solution and the solvent in the mixture of the aqueous solution and the solvent. The invention is based on two facts. The apparatus further comprises a control unit for controlling the first and second light-emitting elements to alternately emit light for deciding a print medium material based on a reflection amount of light received by the light-receiving element and establishing print conditions adapted to the print media.