How do I clean black wallpaper from old radiator oil?

Have you tried a vinegar / water solution?

The soot is very oily. You need a degreasing cleaner. TSP, trisodium phosphate or Krud Kutter.

Marisa, I could not find information exactly on this subject, but this video was in among the ones of removing dirt from your type of heating. I hope this works for you, if it doesn't, come back and we will try something else.

https://www.youtube.com/watch?v=edXGsrMvNsA

Use degreaser and do not rub it you'll push it into wallpaper fibers dab it/blot it

Hi Marisa, have you tried pretreating it with a diluted light grease cutter like simple green , dab it off, then use a steamer and dab to remove the oil, don't wipe as you may remove the paper

The black is oil based and Krud Kutter will cut it. Buy original concentrate. Put in a spray bottle and add water. Spray, wait a minute, wipe off. No smell.

Oil-based stains are not going to come out of paper.

Soap would cut the oil on a non-absorbent surface.

I would try an orange-oil based cleaner, or other grease-cutting cleaners.

But honestly, it sounds like a too tough problem.

I would start looking for a glass shop that will sell me a large piece of factory frosted tempered glass (or a pre-made frosted shower door replacement panel).

I would use mirror clips & fasten it to the wall behind the radiator.

Before that I’d use tinted stain-blocking primer on the area where the glass paneling will go.

I can’t think of another non-combustible paneling product that will take the serious cleaning required, sorry.