Tam sim no, lub hoobkas muaj cov khoom siv raw txaus, tag nrho cov uas yog los ntawm cov chaw tsim khoom hauv tsev. Tom qab txhua pob ntawm cov khoom siv raw tuaj txog, peb lub tuam txhab yuav ntsuas tag nrho cov khoom, hardness, hardness, tensile dag, thiab loj.
Thaum tsim nyog, lawv yuav muab tso rau hauv cov khoom siv khoom siv khoom siv.