 Color changing heat transfer
Hello,
I am hoping someone can help me out with this. My brother recently came to me with a shirt that had (what appears to have been) a heat transfer that when you went out into the sunlight a ghost background image appears. The design looks like a regular black artist sketch when worn indoors but when it is exposed to sunlight a red background image appears. Does anyone know what type of process or transfer is used to get this effect?
Thanks,
PCG | 
