To a small dish, add baking soda.

Pour lemon juice over baking soda. It will begin to foam immediately.

Mix with a spoon to form a thick paste.

Use immediately on your tub, tiles and sinks by applying a thin layer all over with a sponge, gently scrubbing any tough or extra-dirty spots. Let cleaner sit for 10 minutes, then rinse well with warm water until any gritty residue is gone.