I've used my heavy-duty steamer to remove wallpaper from every room of my house without much trouble. The steam method always left behind clean, smooth, plaster, ready for painting.
However, in my kitchen, the plaster walls and ceiling were covered in canvas or linen that was also painted over. It was bubbled and peeling, not to mention total paint failure. I was able to grab this fabric and peel it from the walls without too much effort and no damage to the plaster. Extremely messy as the paint turned to dust and chips flew everywhere when the fabric was pulled.
From the known history of my house, I am guessing this fabric was applied sometime before the mid 1970's, but that only narrows it down to ~70 years.
Now it's time to repair the plaster and prep the walls for paint. The problem is the brown/tan (dark orange?) glue residue left behind and the very rough surface it created. I don't know what it is but it does not want to dissolve as easily as wallpaper paste. I've hit it with the steamer, I've tried scrubbing, vinegar (bad idea - hurts lime in plaster), nothing seems to work on this stuff. After a huge amount of labor on a small area, I can start to see some small blotches of white plaster showing through, but it's far from ready.
It's very dry, crumbly, and the wall surface feels like sandpaper. Brown/tan in color, but has a burnt orange appearance that might be an optical illusion. When wet, it does not feel slimy like wallpaper paste. Scrubbing with a wet sponge and stiff plastic bristle brush, produces a residue and smooths the surface a bit, but it's barely making a dent in this stuff. Wet heat from the steamer seams to have no more of an effect than the scrub brush... I was really expecting it to dissolve and wipe away like wallpaper glue.
What's making this project seem even more daunting is that the ceiling was also covered in this mess.

What kind of glue could this be? Is there a test so I can determine what this stuff is? Once determined, maybe then a plan of attack can be figured out. There is also a lot of woodwork in its original shellac or varnish, so I prefer to avoid using paint stripping chemicals if possible.
Thank you for any help and suggestions.