When all is not fine with your melamine
MELAMINE or melmoware is a thermosetting plastic. This is hard and smooth and keeps its shape well. It could be broken by hard blows. It is strong, lightweight and hard, but can be scratched or broken or cracked. It resists acids and alkalis, and most food stains but can be stained. It also stands fairly warm temperatures, but absorbs heat and softens if it gets too hot so cannot be used in microwave ovens. It's used for dinnerware, mixing bowls, laminated counter tops, and other items.
Dishes that have chips,
cracks, and scratches can be cleaned, but burn marks cannot be removed.
The absolute safest way to clean them is just plain warm water. As you
can imagine, that doesn't always clean the dishes thoroughly. There
really is no "finish" applied to melamine dinnerware; the
sheen on factory-new dishes is a result of the extreme pressure and heat
applied during the molding process.
Another safe and effective method for cleaning melamine is a mixture of liquid dish soap and warm water with a soft cloth. For removing grime in the "corners", use a soft toothbrush. Start brushing away the dirt. The stuff in the raised lettering on the bottom is tough to get out, and requires some patience and maybe a stiffer toothbrush. Never wipe off excessive dirt or dust with a dry rag. This will scratch the dishes. Rinse with warm water and use the soap, then wipe lightly. Dishes with caked-on dust can be successfully cleaned with just a warm water rinse and soap.
Don’t leave a mark
The residue from price stickers, scotch tape, masking tape, etc, is best removed from melamine with mineral spirits or paint thinner. Thinners and mineral spirits aren't great, but work well if that's all you've got. Just don't get sloppy; put some on a paper towel or a soft cloth and rub lightly. Soap and rinse immediately afterwards.
Grease pencil and magic markers are a huge problem, especially if they've been on the dishes for a long time. Clean as soon as possible, as it appears the longer it's been on the dishes, the more of a chance the grease and marker will permeate the finish, leaving a "ghost". It's more of a problem on the whites, yellows, pastels, etc. than on dark colours. Mild doses of bleach can be used for removing markers and grime, but don't leave it on too long as it will discolour dishes quickly. Anything that'll eat the label off it's own container (bleach) is something to watch closely, and guard against. Try putting it on the dishes, let it set for just a minute or so, then start brushing lightly with a soft toothbrush. Usually this is enough to loosen any dirt or grime and dissolve any markers.
What to avoid
There are other precautions to be aware of when using bleach; i.e., use gloves if you have sensitive skin, remove jewellery to avoid oxidation, and wear old clothes for splashing accidents. Be sure to rinse the dishes well after either of these treatments.
While cleaning melamine tableware is not tough, once it gets discoloured with frequent use and washing, it loses its appeal. Since scratches and burn marks cannot be removed from it, perhaps the best solution is to throw out the damaged pieces.
— Chetna Banerjee