[tsimionescu]

I was using "painting" in the broader sense of "man-made work of mostly bi-dimensional visual art".

I'd also say that I'm pretty sure the mysteriousness of the technique is way overblown. Sure, we don't know exactly what it was, but there are trace pigments on the cloth, and ~600 years of handling and being displayed without much protection, plus being doused in water ~500 years during a fire, will wash off pigments in ways we can't fully predict.