Capillary action

Capillary action (sometimes called capillarity, capillary motion, capillary rise, capillary effect, or wicking) is the process of a <a href="/facts/Liquid/t9GkLWzt">liquid</a> flowing in a narrow space without the assistance of external forces like <a href="/facts/Gravitation/bqAN7DdQ">gravity</a>.
The effect can be seen in the drawing up of liquids between the hairs of a paint-brush, in a thin tube such as a <a href="/facts/Drinking_straw/NpPqhNdP">straw</a>, in porous materials such as paper and plaster, in some non-porous materials such as <a href="/facts/Clay/xnwouEkB">clay</a> and liquefied <a href="/facts/Carbon_fiber/6PlL4mB2">carbon fiber</a>, or in a <a href="/facts/Biological_cell/bLM9UQvy">biological cell</a>.
It occurs because of <a href="/facts/Intermolecular_force/xIcFMvL7">intermolecular forces</a> between the liquid and surrounding solid surfaces. If the diameter of the tube is sufficiently small, then the combination of <a href="/facts/Surface_tension/EuluYmSM">surface tension</a> (which is caused by <a href="/facts/Cohesion_(chemistry)/cthgtKKj">cohesion</a> within the liquid) and <a href="/facts/Adhesion/NuVQPk4z">adhesive forces</a> between the liquid and container wall act to propel the liquid.

Capillary action open-in-new

Capillary action