When the distance between particles is getting smaller, the liquid (water) has no place to go and have to go up. That means capillarity increase as particle sizes decreases.

Capillary action occurs when the adhesion to the walls is stronger than the cohesive forces between the liquid molecules. The height to which capillary action will take water in a uniform circular tube (picture to right) is limited by surface tension and, of course, gravity.

Capillary rise is the height to which the water rises within the tube, and decreases as the width of the tube increases. Thus, the narrower the tube, the water will rise to a greater height.

Capillary Action Formula The rise of a column of liquid within a narrow capillary tube is also because of the surface tension. The formula for capillary rise (h) = 2T/[rρg].

Weight of the liquid in the tube is supported by adhesive force. When the diameter of the tube decreases, the weight of the liquid it can contain also decreases. The adhesive force with the tube is greater than the cohesive force of the liquid. Capillary rise increases with the decrease in the diameter.

The capillary rise is inversely proportional to the tube radius. It can be also applied to the case where the liquid level in the tube decreases below the outer liquid surface; this situation happens when θ=90°.

In short, the capillary action is due to the pressure of cohesion and adhesion which cause the liquid to work against gravity. Here again the cohesive forces per unit mass are higher when the surface area to volume ratio is higher. This happens for capillary tubes of smaller diameter.

The rise of water in a thin tube inserted in water is caused by forces of attraction between the molecules of water and the glass walls and among the molecules of water themselves. The narrower the bore of the capillary tube, the higher the water rises.

The meniscus is the curve caused by surface tension in the upper surface of a liquid. Conversely, a concave meniscus occurs when the molecules of the liquid are attracted to those of the container, causing the surface of the liquid to cave upwards. This can be seen in a glass of water.

Capillary action and root pressure can support a column of water some two to three meters high, but taller trees–all trees, in fact, at maturity–obviously require more force.

so if we increase the temperature, the density of most of liquid decreases this causes the decrease in surface tension and as well as capillary rise. Another thing increase in temperature leads to expand the material of capillary, this also decrease capillary rise.

Increase capillary action: Increase temperature, decrease capillary tube diameter, perform any number of actions to decrease surface tension, etc…! Decrease capillary action: The opposite of the steps you would take to increase, also, increasing the density of the liquid you’re working with.

Cotton does exibit a capillary like effect although I don’t believe it is technically the same mechanism. Synthetic materials (nylon, etc) would not work as well. Other natural fibers would work (wool has even better wicking abilities) but are much more expensive. I think muslin is your top choice.

Cotton is a commonly recommended wicking material, but some warn that natural materials, like cotton, may rot or contract fungus easily. Wicking materials less likely to encounter this problem include nylon and acrylic.

Wicking beds are great for ensuring your tomato plants have a steady supply of water over the summer months, but they can be problematic in heavy rain as the roots can stay too wet. If you haven’t planted with manure then top-dress with some slow-release organic fertiliser.

Lettuces love to be kept moist and are ideal to grow in a wicking bed. Mulch the bed, with about 50-70mm of organic mulch, such as straw. Water the bed well, to start the wicking-action.