In 2000, the author and his team reported on the effects of the heat supply and the nip pressure from an aspect on energy supply to toner in Japan. [1] They found in typical roll fusers that influence of nip width enhancement, only by hardness reduction for back-up roll elastic layer without increasing pressing load, to fixing strength is very little. It provided that fixing strength contour in coordinates of heat supply and pressure. As a result, the contour diagram could derive design concepts and procedures for basic specifications in roll fusers.The prior study described above contains some outstanding issues, especially for the mechanism solving, which should be examined. The thermal energy represented by the heat supply was discussed in it. However, absorbed or latent heat should be examined and aspects from rheology should also be provided, for comparing pressing work. In the present report, the prior study is reviewed and further considerations are provided for the issues.