Tom qab siv sijhawm ntev, cov khoom cua sov yuav dub.
Lub hauv paus ntawm nws txoj kev kho blackening yog ua kom lub ntsej muag huv thiab huv. Yog hais tias muaj impurities rau ntawm nws nto, nws yuav tsis conducive rau blackening kev kho mob.
Thawj qhov uas yuav tsum tau ua yog kom tshem tawm cov organic teeb meem, uas yog, hu ua degreasing kev kho mob. Degreasing yog ib qho yooj yim ua. Hais txog lub degreasing, txhua yam koj xav tau yog degreasing kua.
Tom qab c alkali ntxuav, cov txheej txheem hauv qab no yog acid-ntxuav. Tsis tsuas yog alkaline organic teeb meem ntawm qhov chaw, tab sis kuj acidic organic teeb meem. Yog li kev ntxuav cov kua qaub kuj tseem tsim nyog. Lub acidity yuav tsum yog tus nqi ph ntawm 3, thiab lub sijhawm ua haujlwm tsis tas yuav tsum yog li 10 feeb.
Cov kauj ruam kawg yog kom qhuav lub rhaub. Kev ziab yog tshem tawm cov dej lo rau saum npoo .Thaum kawg, nws yog oiling.
Tom qab kev kho mob saum toj no, nws yuav txhim kho qhov hnav tsis kam ntawm lub tshuab hluav taws xob ntawm lub tshuab hluav taws xob, txhim kho qhov nyuaj ntawm qhov chaw, thiab yuav tsis cuam tshuam rau cov khoom hauv.
