Hi Man Chiu Hui, Celine here. After using vinegar to wash the dry wok, after half an hour, almost half the wok turns rusty. You can use fine sand paper to polish the rust off. First apply some water onto the sand paper to rub off the rust and use a damp cloth to wipe off the rust. Immediately use kitchen paper towel to wipe dry to prevent rush again. Start to heat up the wok all over again.Tks. That means in future when we heat up the wok, can skip using the vinegar step. Directly go to the heating step after washing the wok with warm water and liquid detergent. Tks. Have A Good Day.