What is the black powdery substance between the inner and outer walls of a thermos bottle?
I collect and recycle scrap metal such as brass,copper, aluminum and stainless steel. I am in the process of taking apart a thermos bottle witch has a steel outer wall and a stainless steel inner wall. I cannot recycle either material if they are not separated. .While cutting them apart a black powder like substance began spilling out, there is quite a lot of it, and Im not sure if this is a harmfull material or not and I need to know so that I can disopse of it properly.