Within the walls of my 1950s era home is a strange type of insulation. At first it looks like blocks of foam rubber but when handled it crumbles into fine dust. I've been wearing a standard mask but don't know what this stuff is. It could be something from the 1970s as well because it appears in parts of the house were apparently renovated then. Thanks in advance
What you have is probably foam insulation that was installed with a hose through a hole in the wall. The foam expands and fills the voids in the wall cavity. Early installations (70's-80's) used a foam that, over time, shrank away from the studs and created loose fitting "blocks". The foam also tended to be easily crumbled when touched.