there is disclosed a process for preparing novel tacking agents for glass fiber insulation . the tacking agent solution is prepared by adding a condensed phosphate to an aqueous solution of aluminum orthophosphate to provide a homogeneous solution having an al : p molar ratio of less than 1 , preferably 1 : 3 and wherein the amount of condensed phosphate comprises from about 25 to about 75 percent of the total phosphate in the solution . the tacking agent is applied to glass fiber in the preparation of insulating articles and then heated to convert the tacking agent into a non - hygroscopic , water insoluble , amorphous , condensed aluminum phosphate polymer . the tacking agent resiliently tacks the glass fibers together so as to provide regain of shape after deformation of the fibers as by compression .