Hello Andrew,
I didn't know they made t-shirt with Kapton
Seriously I am always amazed with the constrast control you have with your pictures ! The effect of Pyrocat-HD ?
@Raphael Pyrocat-HD is indeed a special developer, and I suspect it played a role... But, shooting at EI 50 and placing the shadows high on the scale is probably what did it. Probably D-23 1+3 would have done just as well, I think. Cheers!