B

The binder phase (e.g., gypsum in gypsum-bonded or phosphates in phosphate-bonded investments) glues the refractory silica particles together, giving the set investment mold its rigidity and mechanical strength without materially affecting the desired thermal expansion [Yan & Takahashi, 1998, PMID 9893498; Zhang et al., 2001, PMID 11915627].