Why doesn't white tattoo ink show up on my skin?

I'm a caucasian male who has a small (2" x 3") tattoo on my arm. Much of the tattoo is white. When the artist first applied the tattoo she went over the white portion three times. After a 2 week healing period, the white ink was virtually invisible. She reapplied the white portion two days ago and it's only barely visible. Do I need to have it reapplied AGAIN??