[олег назаров]

CakeCannot be so warm! it is dangerous to work. 60 degrees was beyond restoration on irreversible processes go!!!

And this was done so: from the front side included lamp IR ( don't remember what they were called but there were several pieces with different wavelengths) at a decent distance of 2-3 meters the rest of the light was off and was shooting ( nothing to heat is not necessary) extract 20-30 minutes.
The whole point is that different materials on different reflect or absorb the invisible rays of the spectrum and this difference is visible on the film.
heat is nothing to do with.