ᐅ Found any harmful substances in your home?

Hello everyone,

I was just working on a suspended ceiling in my mother’s house using a sanding machine because a window wasn’t opening properly and was rubbing against the ceiling. After sanding off the paint, I noticed a brown underlying material, somewhat like cardboard, which forms small balls or fibers when sanded. I’ve attached a photo – does anyone know what this is and if it’s safe?

Thanks for your help!!
Sebastian

It looks like the packaging of a drywall sheet. Try poking the tip of a utility knife in and see if it’s white behind the brown layer. Also, tap on the surface—does it sound solid like stone or more like 1.25cm (0.5 inch) compressed gypsum? ;-)