What materials will leak through wallpaper and ruin the wall?

Question:I have horse-hair plaster walls (circa the early 1800s) with cheap wallpaper covering them. I would like to mural OVER the wallpaper with glue, acrylics, pen, sharpies, etc. I'm just a little worried about damaging the wall underneath. Think anything might ruin the wall itself? (not discolor, that doesn't matter, just actual erosion or something)

Thanks

Answers:
I too own a historic home with horse hair plaster walls. Really, it sounds like what you want to do would be fine. The BIGGEST culprit for ruining our type of walls would be urine (cat, in particular). If you think of that example, watch your acidic compounds. Also, as far as art supplies go, watch using linseed or other oils. Be careful as well to not useany vibrating tools (ex. a sander, or saw) against the wall. Both could create cracks which can lead to serious repair.


Have fun, stay safe!!