how to raise a tatoo

I have a large tatoo on my back, and an artist friend of mine wants to take a body cast of my back/buttocks/legs for an exhibition. We need to temporarily raise the tattooed area of my skin to get a good cast of that, but can this be done - the cast sets in minutes, but is raising the skin dangerous for the tattoo? Some people have said that heat can raise the scar tissue, but is their any other methods which do not encroach or damage? I don't know if it is possible and if anyone could offer any advice it would be much appreciated :-)