Abstract: A method is described for stabilizing the viscosity of a liquid epoxy-anhydride system which is a blend of a liquid epoxy resin, a liquid anhydride curing agent and a quaternary ammonium salt promoter for an epoxy-anhydride reaction. This system is especially useful in the manufacture of tubing, piping and other geometric structures. The method employs at least one of the following modifications:(1) adding a minor amount of a solid epoxy resin to the liquid epoxy resin;(2) adding to the liquid anhydride a minor amount of solid anhydride of high reactivity;(3) adding to the epoxy-anhydride system a solid resinous particulate material in finely ground form which is capable of reacting with the epoxy resin and acid anhydride, and is soluble in the epoxy-anhydride system at temperatures below the gelation temperature; and(4) adding a metallo-organic compound which lowers the initiation temperature or accelerates the epoxy-anhydride reaction.