ress es ▁from ▁Boston ▁Category : Act ress es ▁from ▁Gre ater ▁Los ▁Angeles ▁Category : V ir gin ia ▁Te ch ▁al umn i ▁Category : Univers ity ▁of ▁Massachusetts ▁Am her st ▁al umn i ▁Category : Activ ists ▁from ▁California <0x0A> </s> ▁An ▁orth op edic ▁cast , ▁or ▁simply ▁cast , ▁is ▁a ▁shell , ▁frequently ▁made ▁from ▁pl aster ▁or ▁fi berg lass , ▁that ▁enc ases ▁a ▁lim b ▁( or , ▁in ▁some ▁cases , ▁large ▁port ions ▁of ▁the ▁body ) ▁to ▁stabil ize ▁and ▁hold ▁an atom ical ▁structures — most ▁often ▁a ▁broken ▁b one ▁( or ▁b ones ), ▁in ▁place ▁until ▁he aling ▁is ▁confirmed . ▁ ▁It ▁is ▁similar ▁in ▁function ▁to ▁a ▁spl int . ▁ ▁Pl aster ▁band ages ▁consist ▁of ▁a ▁cot ton ▁band age ▁that ▁has ▁been ▁combined ▁with ▁pl aster ▁of ▁par is , ▁which ▁hard ens ▁after ▁it ▁has ▁been ▁made ▁wet . ▁Pl aster ▁of ▁Paris ▁is ▁calc ined ▁gy psum ▁( ro asted ▁gy psum ), ▁ground ▁to ▁a ▁fine ▁pow der ▁by ▁mill ing . ▁When ▁water ▁is ▁added , ▁the ▁more ▁sol ub le ▁form ▁of ▁calci um ▁sul f ate ▁returns ▁to ▁the ▁relatively ▁ins ol ub le ▁form , ▁and ▁heat ▁is ▁produced . ▁▁ 2 ▁( Ca SO 4 · ½ ▁H 2 O ) ▁+ ▁ 3 ▁H 2 O ▁→ ▁ 2 ▁( Ca SO 4 . 2 H 2 O ) ▁+ ▁He at