no way lah, my maid also used sponge with 'green area' to clean the milk bottles steamer lah, it turns to black color from silver. She broke 2 plates after coming for around 1-mth. I think it may because of their working style - 粗心大意. Most of them don't treasure what they have lah. Until one day you ask your maid to wash clothes by hands, then she knows how important of the machine!