Technical manuals are tough.
They are waterproofed to an extent, so while soaking gets them wet, it doesn’t get them, um, soaking. I had to keep spraying this down with water, and go very heavy on the fixatif.
You can see the resistance in this ^ shot. A time or two I had to resort to glue.
So, tech manuals, tough to soak, and a pain in the ass to shape, but worth it, I think.