ðeɪ ɑːɹ ðə pɹˈɑːdʌkt ʌv kˈɛmɪkəl ɹɪˈækʃənz, fˈɪzɪkəl ɪfˈɛkts, ænd kəntˌæmᵻnˈeɪʃən ðæt əkˈɜːz dˈʊɹɹɪŋ ðə mˈɛltɪŋ ænd pˈoːɹɪŋ pɹˈɑːsɛs.
They are the product of chemical reactions, physical effects, and contamination that occurs during the melting and pouring process.