AN EMBODIMENT OF THE PRESENT INVENTION PROVIDES A METHOD FOR IMPROVING THE TENSILE STRENGTH OF FOUNDRY CORES AND MOLDS. MORE PARTICULARLY, AN EMBODIMENT OF THE PRESENT INVENTION PROVIDES AN IMPROVED BINDER FOR FOUNDRY CORES AND MOLDS THAT INCLUDE A FLUORIDE BEARING ACID IN COMBINATION WITH AN INORGANIC SILICON COMPOUND. ALTERNATELY, THE IMPROVED BINDER MAY INCLUDE A FLUORIDE BEARING ACID IN COMBINATION WITH A BORON COMPOUND. IN A PREFERRED EMBODIMENT, A MODIFIED PART 1 BINDER COMPONENT INCLUDES A COMBINATION OF HYDROFLUORIC ACID AND AN INORGANIC SILICON COMPOUND.