Kev tsim khoom, lub fatory them sepcial xim rau ib puag ncig prodtaction thiab siv lub zog tshiab.Siv "ntsuab ntiaj teb" raws li kev qhia ntau lawm.
Cov khoom tseem ceeb yog Lead Nitrate, Zinc Sulphate, Sodium Metabisulphite, thiab Sodium Persulphate.
Peb Lub Chaw Haujlwm
