▁within ▁ 1 0 ▁to ▁ 3 0   seconds . ▁Depending ▁on ▁the ▁type ▁of ▁b inder ▁it ▁may ▁require ▁further ▁b aking ▁to ▁fully ▁c ure . ▁C ores ▁produced ▁using ▁this ▁method ▁are ▁sometimes ▁referred ▁to ▁as ▁" shell - core " ▁because ▁often , ▁only ▁the ▁outside ▁layer ▁of ▁the ▁core ▁is ▁hard ened ▁when ▁in ▁contact ▁with ▁the ▁hot ▁core box . ▁When ▁the ▁core box ▁is ▁opened ▁and ▁the ▁core ▁removed , ▁the ▁un c ured ▁sand ▁inside ▁the ▁core ▁is ▁dump ed ▁out ▁to ▁be ▁re used . ▁This ▁practice ▁can ▁also ▁be ▁observed ▁in ▁some ▁cold - box ▁cor em aking ▁practices , ▁though ▁cold ▁box ▁shell - core ▁making ▁is ▁much ▁less ▁common . ▁ ▁In ▁a ▁similar ▁ve in , ▁the ▁cold - box ▁process ▁uses ▁a ▁b inder ▁that ▁is ▁hard ened ▁through ▁the ▁use ▁of ▁special ▁g ases . ▁The ▁b inder ▁co ated ▁sand ▁is ▁pack ed ▁into ▁a ▁core ▁box ▁and ▁then ▁se aled ▁so ▁that ▁a ▁cur ing ▁gas ▁can ▁be ▁introduced . ▁These ▁g ases ▁are ▁often ▁to xic ▁( i . e . ▁am ine ▁gas ) ▁or ▁od orous ▁( i . e . ▁SO 2 ), ▁so ▁special ▁handling ▁systems ▁must ▁be ▁used . ▁However , ▁because ▁high ▁temper atures ▁are ▁not ▁required ▁the ▁core ▁box ▁can ▁be ▁made ▁from ▁metal , ▁wood , ▁or ▁pl astic . ▁An ▁added ▁benefit ▁is ▁that ▁h ollow ▁core ▁can ▁be ▁formed ▁if ▁the ▁gas ▁is ▁introduced