A pair of terms that appear repeatedly in information about absorbent products are "hydrophilic" and "hydrophobic." Although these words may look bookish at first, they’re really easy to tell apart and understand if you look at the parts.

"Hydro" is Greek for "water." You see it in all kinds of words having to do with water such as "hydraulics", "hydroplane", "hydrant", etc.

"Philia" is Greek for "love." It appears as part of words like "philanthropy" (love of people), "philosophy" (love of wisdom), and even "philately" (love of postage = stamp collecting). "Phobos" is Greek for "fear." Any number of "phobias" are well-known, such as acrophobia (fear of heights), claustrophobia (fear of closed spaces), and ailurophobia (fear of cats).

With this explanation as a memory aid it’s easy to recall that "hydrophilic" or water-loving absorbents are absorbents that readily absorb water and water-based liquids; "hydrophobic" or water-fearing absorbents are absorbents that repel water, but absorb oils – in fact they sometimes are also called "oleophilic," which means "oil-loving."

Hydrophilic absorbents are often called "general-purpose" absorbents, as they will absorb almost all liquids. Technically a hydrophilic molecule or portion of a molecule is typically charge-polarized and capable of hydrogen bonding, enabling it to dissolve more readily in water than in oil or other hydrophobic solvents.

Hydrophilic absorbent materials resist no liquids: they soak up water-based and petroleum-based liquids alike. These are, therefore, useful as Universal / Chemical absorbents or HazMat absorbents.

Hydrophobic substances tend to be non-polar and thus prefer other neutral molecules and non-polar solvents. Water on the surfaces of hydrophobic substances will exhibit a high contact angle; that is to say, the water will bead up rather than spreading out and soaking in.

Hydrophobic materials are used for oil removal from water, the management of oil spills, and chemical separation processes to remove non-polar from polar compounds.

Because of the typical difference in polarity, hydrophilic and hydrophobic molecules are also known as polar molecules and nonpolar molecules, respectively.

As a further aid in identification, most oil-only absorbents that repel water and only absorb oil and other hydrocarbon products have a white color that makes it easy to see when they're saturated. They are available in a variety of forms besides loose, including oil absorbent pads, rolls, mats, socks, pillows, booms, bags, and even pompoms, and are especially valuable in locations with a high oil-spill potential, such as machine shops, garages, and refineries, and in waterside locations such as marinas, dockyards, and marine terminals.

The general-purpose hydrophilic absorbents come in a variety of colors and at least as many formats as do the oil-only products.

Knowing just a bit about Greek will help you keep them as separated in your mind as water is from a hydrophobic surface.