Salts/damp spots coming through plasterboard

[cooket3]

I live in an old house with stone walls. My plaseterer dot and dabbed the plasterboard on the wall. For some time I thought they were dam spots. I have put my fire on and dehumidifier and doesnt help that much. I now think that the salts/minerals are being absorbed from the stone through the dot and dab to the plaster board as the plasterboard is not dam and looks like its reacting with something.

Obviously they do not look good. Is there a paint that will stop this coming through? I know there is hammerite etc for outside, however I was wondering if there is anything more friendlier to use indoors

Thank You

 

[endecotp]

Can you post photos?

Is it possible that these are cold spots, due to the dabs conducting heat, and you are getting condensation there?

 

[bobasd]

sounds like penetratin damp comin through the dabs of adhesive - a very common thing esp. in stone walls.
salts in the penetratin damp will attract condensation sometimes so you might have penetratin damp an condensation.

no paint or so called damp proofin liquid will permanently stop what youve got

are the walls rendered on the outside?