um ▁AD . ▁F rit ▁was ▁a ▁significant ▁ing red ient . ▁A ▁reci pe ▁for ▁“ f rit ware ” ▁d ating ▁to ▁c . ▁ 1 3 0 0 ▁AD ▁written ▁by ▁Ab u ’ l ▁Q as im ▁reports ▁that ▁the ▁ratio ▁of ▁quart z ▁to ▁“ f rit - glass ” ▁to ▁white ▁cl ay ▁is ▁ 1 0 : 1 : 1 . ▁This ▁type ▁of ▁pot tery ▁has ▁also ▁been ▁referred ▁to ▁as ▁“ stone ware " ▁and ▁“ f ai ence ” ▁among ▁other ▁names . ▁A ▁nin th - century ▁cor pus ▁of ▁“ proto - stone ware ” ▁from ▁Bag hd ad ▁has ▁“ re lict ▁glass ▁fragments ” ▁in ▁its ▁fabric . ▁The ▁glass ▁is ▁alk ali - lime - le ad - sil ica ▁and , ▁when ▁the ▁paste ▁was ▁fired ▁or ▁co o led , ▁woll ast on ite ▁and ▁di op side ▁cry st als ▁formed ▁within ▁the ▁glass ▁fragments . ▁The ▁lack ▁of ▁“ in clus ions ▁of ▁cr ushed ▁pot tery ” ▁suggests ▁these ▁fragments ▁did ▁not ▁come ▁from ▁a ▁gla ze . ▁The ▁reason ▁for ▁their ▁addition ▁would ▁be ▁to ▁act ▁as ▁a ▁flux , ▁and ▁so ▁“ ac cel er ate ▁vit r ification ▁at ▁a ▁relatively ▁low ▁firing ▁temperature , ▁and ▁thus ▁increase ▁the ▁hard ness ▁and ▁density ▁of ▁the ▁[ cer am ic ] ▁body .” ▁ ▁Middle ▁( 1 2 0 0 – 1 4 0 0 ) ▁ ▁By ▁this ▁period ▁the