18K gold contains less gold, so it is lighter and harder. 24K gold is pure gold, which feels heavy when you get started and has a heavy texture. 18k is very light and does not need demoulding. 18k indicates that the purity of gold in jewelry is 18K. 18K is not weight, but proportion. Theoretically, the gold content of 100% is 24K. In fact, gold with a purity of 100% is impossible. Our country stipulates that gold with a purity of over 99.9% is 24K.