Fusion and fix of images is an important process in digital printing. A base toner is mainly composed of a polymeric binder and a pigment with and without an internal lubricant for fuser roll. Necessary step in fusion of toner after particles melt is coalescence of particles. A review of models of coalescence of particles finds that rate of calescence is dependent on toner particle size, its viscoelastcity and its surface tension. Rolling contact analysis can be used to calculate temperature and shear rate during roll fusing. Temperature and strain rate dependent toner viscoelasticity (viscosity and compliance/modulus) is affected by important variables such as entanglement molecular weight and morphology of a binder polymer. Compared to fusion of toner image, fixing of an image takes place continually as the toner temperature drops. Eventually, adhesion and fixing of the toner image to a substrate is tested at ambient temperature where shear and flexural stresses dominate. Unlike fusion, the effect of molecular weight and morphology of a binder toner is different on image fix because of their effect on brittle - ductile transition and toughness (modulus) of a toner.