Nta
1 Zoo heev txo tus kheej tawg tus nqi ntawm iav.Los ntawm kev ua kom NIS nthuav dav ntawm cov iav tempered hauv cov txheej txheem cua sov so, tau daws qhov teeb meem ntawm tus kheej tawg.
2 Kev ruaj ntseg zoo heev.Piv nrog rau cov iav tempered ib txwm, qhov spontaneour breakage ntawm tshav kub soaked iav tau poob rau ib ncig ntawm 3‰.
3 Superior zog kev ua tau zoo.Lub khob sov so yog 3 ~ 5 zaug muaj zog dua li cov iav qub ntawm tib lub thickness.
4 Tus nqi rau cov iav sov so yog siab dua iav tempered.