▁This ▁important ▁metal ▁is ▁an ▁al loy ▁composed ▁of ▁co pper ▁and ▁tin , ▁in ▁proportion ▁which ▁vary ▁slightly , ▁but ▁may ▁be ▁normally ▁considered ▁as ▁nine ▁parts ▁of ▁co pper ▁to ▁one ▁of ▁tin . ▁Other ▁ing red ients ▁which ▁are ▁occasionally ▁found ▁are ▁more ▁or ▁less ▁accident al . ▁The ▁result ▁is ▁a ▁metal ▁of ▁a ▁rich ▁golden ▁brown ▁colour , ▁capable ▁of ▁being ▁worked ▁by ▁casting ▁— ▁a ▁process ▁little ▁applicable ▁to ▁its ▁component ▁parts , ▁but ▁peculiar ly ▁successful ▁with ▁bronze , ▁the ▁density ▁and ▁hard ness ▁of ▁the ▁metal ▁allowing ▁it ▁to ▁take ▁any ▁impression ▁of ▁a ▁m ould , ▁however ▁del icate . ▁It ▁is ▁thus ▁possible ▁to ▁create ▁orn amental ▁work ▁of ▁various ▁kinds . ▁ ▁The ▁process ▁of ▁casting ▁is ▁known ▁as ▁c ire ▁perd ue , ▁and ▁is ▁the ▁most ▁primitive ▁and ▁most ▁commonly ▁employed ▁through ▁the ▁centuries , ▁having ▁been ▁described ▁by ▁the ▁mon k ▁The oph ilus , ▁and ▁also ▁by ▁Ben ven uto ▁Cell ini . ▁Br ief ly , ▁it ▁is ▁as ▁follows : ▁a ▁core , ▁roughly ▁representing ▁the ▁size ▁and ▁form ▁of ▁the ▁object ▁to ▁be ▁produced , ▁is ▁made ▁of ▁p ounded ▁brick , ▁pl aster ▁or ▁other ▁similar ▁subst ance ▁and ▁thoroughly ▁d ried . ▁Upon ▁this ▁the ▁artist ▁over l ays ▁his ▁w ax , ▁which ▁he ▁models ▁to ▁the ▁degree ▁required ▁in ▁his ▁finished ▁work . ▁Pass ing ▁from ▁the ▁core ▁through ▁the ▁w ax ▁and ▁project ing ▁beyond ▁are ▁metal ▁ro ds .