An aqueous coating fluid is described comprising gelatin at a concentration of at least 1 wt % and a colloidal particle dispersed material phase at a volume fraction of at least 0.01, wherein at least 20% of the gelatin comprises a gelatin prepared from hydrolysis of ossein using sodium or potassium hydroxide. The present invention enables increasing the concentrations of a coating fluid containing gelatin and dispersed sub-micron colloidal materials, reducing the size of the sub-micron colloidal materials in such a coating fluid, and/or including higher molecular weight gelatin in such a coating fluid without detrimentally increasing the viscosity of such fluids. The invention further enables reducing the viscosity of an aqueous coating fluid containing gelatin and dispersed insoluble colloidal material, without needing to reduce the concentration of gelatin or colloidal materials, increase the size of the sub-micron colloidal materials, and/or reduce the molecular weight of the gelatin. Each such advantage may be achieved either individually, or in combinations to varying extents, without the need to fundamentally change the composition of the materials in the coating fluid.