The structure-property relationships of C\sb60 dissolved in decahydronaphtalene (decalin) and a petroleum solvent viscous standard (PSVS) were studied. This work was motivated mainly by the interest to improve fullerene dispersion in powder processing and the development of a viscoelastic standard for commercial use. Decalin was selected based on the amount of fullerene it can hold, the toxicity grade, rate of evaporation, and inability to interfere with the test method. The PSVS is a standard for viscous calibration of rheological instruments. Measurements of solubility, density, viscosity and elasticity values were conducted. The results are for samples classified as 0, 25, 50, 75 and 100% of C\sb60 saturation level. Decalin can dissolve 1.9 mg/ml of C\sb60 while the PSVS only dissolves 0.15 mg/ml. The viscosity behavior shown by both solvents was Newtonian, with a small increase in viscosity as a function of fullerene concentration. The elastic portion of the solvents did not change with fullerene concentration.