Cleaning tip of the day: how to clean Lego.Lego is fantastic. However, you might find that the blocks are covered with a layer of dirt that does not go away with simple dusting. Not nice when children are playing with them. The most effective way to remove the dirt is by putting the Lego pieces in a bag and putting it in the washing machine. While the process might be noisy, it is definitely going to clean your pieces well and allow for safer use.