What we commonly refer to as "capillarity" or "capillary effect" is nothing else but the combined effect of various forces acting in the electrical double layer area. One of the most important phenomena are electrokinetic forces or phenomena.
In liquids, electrokinetic phenomena are associated with the thin electrical double layer and occur at nanometer level at the solid-liquid boundary (e.g. a porous wall surface and water, or water and salt crystals).
Electrokinetic phenomena (electro = electric, kinetic = motion) study fluid flow or particle motion under the influence of a voltage or electric field or vice-versa: electrical effects generated by moving liquid or particles driven by pressure, concentration or gravity.
Some electrokinetic phenomena describe the movement of a fluid (water) inside fixed porous materials (walls) under the influence of various external forces. Others describe the movement of suspended particles (salts) in surrounding liquids (water) under the influence of various forces.
The chart below summarizes the most important electrokinetic phenomena, grouped in a logical sequence.
Although there is no need to go in more details about these phenomena, what you need to know:
- They do exist
- They all play a part in the existence of rising damp
- They interact with each other in a complex way
The bottom line: a number of complex molecular phenomena contribute to the existence of rising damp.
For anyone who is interested, here is a brief description of them.
Liquid movement inside porous building materials
- Osmosis (also known as capillary osmosis or diffusion osmosis) [concentration > movement]: the motion of liquid in a porous material (osmotic flow) under the influence of chemical concentration differences (e.g. different areas of salinity)
- Electro osmosis [electric potential > movement]: the motion of liquid (electro-osmotic flow) in a porous material under the influence of an electric potential/field. The opposite of streaming potential.
- Streaming potential [movement > electric potential]: electrical potential generated by fluid moving through a porous material. The opposite of electro-osmosis.
Solid particles moving (floating) inside a liquid
- Diffusionphoresis [concentration > movement]: the motion of particles under influence of chemical concentration differences
- Electrophoresis [electric potential > movement]: the motion of particles under the influence of an electric potential or field.
- Sedimentation potential [movement > electric potential]: an electric potential generated by particles moving under the influence of gravity.