If you ask a building professional about what rising damp is, the typical "scientific" answer you get is "capillary action" - and that's where scientific explanation usually stops.

But what is capillary action? Why it occurs? What drives it? The real scientific explanation only starts here.

Recent Scientific Breakthroughs

Capillary action is the combined effect of several molecular mechanisms that drive the movement of water upwards inside wall capillaries. These include a combination of electrokinetic phenomena, pressure induced flows as well as other potential drivers.

Electrokinetics is a specialized branch of electrochemistry or surface chemistry that studies the motion of fluids and particles under the effect of an electric field, and includes phenomena such as electroosmosis (the movement of fluids under the influence of an electric field), and electrophoresis (the movement of particles in a liquid under the influence of an electric field).

This field has undergone explosive development during the past 10 years, as a better understanding of molecular phenomena near different surfaces can open the door to brand new technologies and materials in the fields of medicine, biochemistry, nanotechnology, engineering, solar cells, batteries etc. Due to their immense growth potential, these fields have spent countless billions on research, resulting in some significant breakthroughs in recent years.

An important field of research is microfluidics, which studies the behavior, control and manipulation of various liquids (water or other solutions) in very small (micro- or nanoscale) channels - making these findings particularly relevant to a better understanding of capillary phenomena inside damp walls.

Electroosmosis - New Discoveries

The study of electroosmosis dates back to as early as the 1960s, but due to the complexity of the phenomena the mathematical modeling was falling behind and was not able to describe more complex aspects of electroosmosis.

The electroosmotic pumping effect achieved with high DC voltages (typically several thousands of volts) has been known and studied for quite some time. The effect of AC or pulsed voltages onto charged capillaries has not been studied until recently, as the phenomenon was significantly more complex. However recent studies have confirmed, that small AC voltages can create in small capillaries pumping pressures of hundreds of atmospheres (bars), resulting in a significant pumping effect.

Electroosmotic flow in a capillary

One of the major recent breakthroughs of this field was the discovery of the induced charge electroosmosis phenomena - the fact that small external fields can generate (induce) an electroosmotic flow, resulting in an electroosmotic pumping effect along the capillary walls. 

Here is a short interview with Prof. Martin Z. Bazant from MIT, a leading authority and researcher of these phenomena explaining the background and findings of his recently discovered induced charge electroosmosis phenomenon.

Here is a summary in plain English of the most important concepts:

  • Electrokinetic phenomena study the motion of particles and fluids in response to an electric field. This area has advanced significantly during the past 10 years.

  • While bulk liquid is neutral, near the capillary walls the existence of surface charges creates an imbalance of positive and negative charges, resulting in an electrically charged layer along the capillary walls called the electrical double layer.

  • Electroosmosis in real life is a very complex phenomenon. We try to understand and describe the movement of a fluid carrying irregularly shaped particles (referred to as "broken symmetries") in irregularly shaped capillaries with variable surface charges. These are a lot of variables that create a very complex set of phenomena.

  • Various early mathematical models have done a lot of simplifications (e.g. assuming perfect sphere particles moving in perfect cylindrical capillaries), and these were not able to describe the significantly more complex real life phenomena.

  • Science can not always explain real life phenomena, the theoretical description can significantly lag behind. E.g. the discovery of electrophoresis - the movement of charged particles under the influence of an electric field. The phenomenon has been discovered in 1808; yet for a 100 years it could not be explained scientifically. The theoretical description and explanation only arrived 100 years later in 1908.

  • Low-frequency AC or pulsed fields create electroosmotic flows resulting in the movement of water along the capillary walls. Irregular particles can also move sideways or even spin under the influence of an AC field.

Rising Damp IS an Electronic Phenomenon

Based on the latest research we can conclude that capillary action in a porous wall fabric is an electronic phenomenon primarily driven by external fields, where the induced voltage in the electrical double layer area of an electrically conducting liquid (salty water), results in an electroosmotic flow and a pumping effect of water along the wall capillaries.

This discovery opens the door to new technologies in handling rising damp, which by altering the surrounding electric or magnetic fields can decrease, nullify or reverse the capillary effect.