Studies on dialysis of aqueous shellac solution have been carried out for ascertaining selectivity between normal and dewaxed shellac and determining the optimum dialysis time for formation of shellac hydrosol. The escape behaviour shows that half-escape time for both the shellac is same and they may be used for hydrosol preparation. Optimum dialysis time has been ascertained by computation of time with resin concentration, pH and volume of the diffusate.