In an image forming apparatus that outputs a reference clock, divides the outputted reference clock based on a set multiple, and generates an image clock based on the division, a width of a synchronization signal that indicates dynamic deviation characteristics is detected, and the multiple is set in accordance with the detected width of the synchronization signal. The method involves combining at least two reactants, a peroxygen source and an acyl group donor to form peracetic acid. Under natural condition, the degraded material can be utilized by microorganism to release carbon dioxide and water, and acts as an eco-friendly plastic material.