All of my house is plastered with old lime plaster, some of it directly onto brickwork, but mostly dry lined onto laths. There are lots of places where the plaster has been damaged by water ingress and the result has been hygroscopic salts. I can't seem to find a way to stop the salts, even though there is no more water ingress. I've heard there is a way of neutralising the plaster. I've tried a poultice of chalk, but this hasn't worked. Any ideas?