Capillary Action

capillary-action-experimentOur SGS PSI General Manager, Cynthia Rancourt, spends her days making sure our world-class independent testing labs run smoothly and deliver excellent results for our clients. One thing you should know about Cynthia is that she has another very important role in life: Grandmother. She goes by “Grandy” and has a lot of “little scientists” that hold her in high esteem. This year, she purchased KiwiCo Kit subscriptions for them, to encourage their curiosity and pursuit of knowledge, specifically in STEAM fields. While they are only between 4 and 6 years old, she strongly believes that it’s never too early to get their young minds primed for lifelong learning!

The most recent experiment was about “capillary action” and how, thanks to this scientific phenomenon, liquids can ‘defy gravity’ by moving up. More specifically, it was a lesson in how plants use capillary action to absorb water and nutrients from soil.

The kit provided three dyes: red, orange, and yellow. The orange color was made by mixing the yellow and the red dye. When the experiment was initiated it was immediately clear that the yellow dye moved at the quickest rate, followed by the orange, with the red lagging behind. Watching a flower change color was super fun, and led to an important question: why did the dye move at different rates?

Capillary action is the movement of liquid–and all the things contained in it–through a porous material. Principles of adsorption and surface tension come into play. The liquid will move up into the capillary–or porous material — and carry soluble components, in this case dye molecules, until the force of gravity is too much to overcome. You experience this when you use a paper towel to dab up spilled liquid. If you were to dip just the edge of the paper towel into the puddle, you would notice the liquid climb up.

This phenomenon makes many natural processes possible. Plants absorb nutrients and water around their structure using capillary action; our eyes’ tear ducts constantly replace fluid by a similar mechanism.

So why did the colors move at different speeds? Each different color in the KiwiCo Kit differed in its affinity toward the porous substrate  which affected the dye’s ability to travel upward at the same rate as the water. The yellow dye, for example, had the lowest affinity to the porous substrate, so it rose with the water farther up than the rest of the dyes.

We put this science into action across a number of our labs and within a variety of technical capabilities. Gas Chromatography and liquid chromatography rely on the principle of the differences in affinity of molecules to the solid stationary phase of the chromatography column and to the liquid mobile phase, to separate mixtures of volatile or soluble molecules.

We’re so happy that companies like KiwiCo exist. Preparing the next generations of young minds is so important to us and is something we’re committed to at SGS Polymer Solutions.