▁is ▁given ▁a ▁profile ▁corresponding ▁to ▁the ▁inside ▁shape ▁of ▁the ▁finished ▁bell , ▁and ▁d ried ▁with ▁gentle ▁heat . ▁Graph ite ▁and ▁wh iting ▁are ▁applied ▁to ▁form ▁the ▁final , ▁smooth ▁surface . ▁ ▁The ▁outside ▁of ▁the ▁m ould ▁is ▁made ▁within ▁a ▁per for ated ▁cast ▁iron ▁case , ▁larger ▁than ▁the ▁finished ▁bell , ▁containing ▁the ▁lo am ▁mixture ▁which ▁is ▁sh aped , ▁d ried ▁and ▁smooth ed ▁in ▁the ▁same ▁way ▁as ▁the ▁core . ▁The ▁case ▁is ▁invert ed ▁( mouth ▁down ), ▁lower ed ▁over ▁the ▁core ▁and ▁cl amp ed ▁to ▁the ▁base ▁plate . ▁The ▁cl amp ed ▁m ould ▁is ▁supported , ▁usually ▁by ▁being ▁buried ▁in ▁a ▁casting ▁pit ▁to ▁bear ▁the ▁weight ▁of ▁metal ▁and ▁to ▁allow ▁even ▁cool ing . ▁ ▁Histor ically , ▁before ▁rail ▁or ▁road ▁transport ▁of ▁large ▁b ells ▁was ▁possible , ▁a ▁" bell ▁pit " ▁was ▁often ▁d ug ▁in ▁the ▁grounds ▁of ▁the ▁building ▁where ▁the ▁bell ▁was ▁to ▁be ▁installed . ▁Mol ten ▁bell ▁metal ▁is ▁pou red ▁into ▁the ▁m ould ▁through ▁a ▁box ▁l ined ▁with ▁found ry ▁sand . ▁The ▁founder ▁would ▁bring ▁his ▁casting ▁tools ▁to ▁the ▁site , ▁and ▁a ▁furn ace ▁would ▁be ▁built ▁next ▁to ▁the ▁pit . ▁ ▁Bell ▁tun ing ▁ ▁Lar ge ▁b ells ▁are ▁generally ▁around ▁ 8 0 % ▁co pper ▁and ▁ 2 0 % ▁tin ▁( bell ▁metal ), ▁which ▁has ▁been ▁found ▁empir ically