I love these little cards and they keep the kids busy for a long time scratching and scratching to get all of the black stuff off and reveal the picture underneath.
I thought these would be messy and we'd have black stuff all over but it really wasn't that bad. If the weathers nice, You can always do it outside if you're worried about any little residue.
For the price this is a really nice set and provides a lot of play value for small kids.