Rising damp is where ground water rises up a masonry wall due to the rise of liquid water through the capillaries of the masonry.
The signs of this rising damp are a tide mark of water about one metre up the wall and salts emerging from the wall onto the surface.
This is termed efflorescence. The salts cause the surface of the wall to break up due to crystallization and this changes with time.
The only method to permanently fix rising damp is to install a new damp course at the base of the wall.
An innovation in fixing or curing rising damp is the use of a silicone cream which is high in concentration of active silanes to penetrate the diameter of the wall producing a water repellent layer as the new damp course.