Identifying and removing distemper
If it’s an old house you may find distemper which is an old form of paint made from whiting and glue. This will appear slightly soft and if you wipe your hand over it may be dusty or powdery.
This is useless for accepting new decoration. It must either be removed or sealed.
To remove it you can use the same method as for stripping paper.
Sealing distemper and dusty surfaces
If this proves impossible or some residue is left behind, then a coat of oily sealer or stabilising solution is the answer.
This is rather liquidy but applied like paint either by roller (messy) or large brush. It percolates into the distemper binding it together and holding it firmly onto the surface.
Failure to deal with distemper will lead either to new paint flaking off, or to the new paper failing to adhere properly.