Long long ago I was a tattoo artist. With very careful needle adjustments, color choices, and a steady hand, this is already possible with conventional inks. Simple example: white ink is titanium oxide, basically sunscreen, and breaks down rapidly with exposure to UV. But you are still gonna have scarring and roughening. If you're gonna get ink, be prepared to have it for life. Also, testing on pigs? Like, live pigs?…
A friend's daughter does tattooing, and from the friend I heard that apprentice artists work on pigskin. I had imagined footballs, but no, this is obtained from slaughterhouses or butchers. Anyway, I guess that footballs aren't made of pigskin.
But they are talking about tattoos that fade because they are broken down by a biological process, which makes me giggle picturing Arnold The Pig with "Born 2 Trot" on his hock.