The effects of bead fusion in the pattern on foam degradation and on casting formation have been studied. Injection molded ASTM D638 tensile specimens have been used to develop a microscopic technique to quantify the extent of bead fusion in the pattern. The tensile properties of the polymer have been correlated with the measured degree of bead fusion. A variety of experiments have been conducted to highlight the effects of fusion on foam degradation. The flow behavior of a molten aluminum alloy has been studied in patterns with various levels of fusion. The results indicate that the degree of fusion has a significant effect on bead collapse and viscous residue formation in the polymer. The mold fill times generally increase with increasing bead fusion in the pattern. The temperature at the metal front drops more rapidly as the bead fusion increases. (C) 2003 Kluwer Academic Publishers.