Get the inside scoop on sock fillers to understand which liquids each sock can absorb.

Editor’s note: Welcome to the fifth post in our series on Absorbent Training. We hope you find the series to be helpful in explaining the basics of absorbents.

From the outside, one absorbent sock looks pretty much like the rest: it’s a tube filled with something and tied on both ends. We make PIG Socks with a tough, absorbent polypropylene skin that draws liquid into the filler and keeps the sock intact when it’s saturated so it doesn’t fall apart when you pick it up.

Socks come in gray, blue, white, and pink. The color will tell you what family the sock belongs to, but like meeting someone new — what makes them special is on the inside. That’s why matching the best filler to your application can often save you time and money.

Here’s the inside story on the most common sock fillers.

Corn Cob

Our PIG Original Absorbent Sock is filled with select ground corncob. The super-sponginess of this filler makes it a good choice for quickly soaking up oils, coolants, solvents and water. It’s also lighter and much more absorbent than clay, so it’s more efficient and easier to use. Corncob is cellulose, which means:

  • it will make an excellent candidate for fuels blending and incineration
  • it is biodegradable
  • it is not the best choice for absorbing corrosives (acids, bases or oxidizers)

Cob-filled socks are the least expensive way to soak up leaks and drips from machinery, or water from doorways and windowsills. They are good at diking liquids, which makes them a good choice for containing spills during routine maintenance.


If you need to stop a spill fast, vermiculite-filled PIG Blue Socks are the way to go. Vermiculite, which is an earthen mineral, has a consistency that is similar to sand and is very absorbent and fast wicking. This lets the sock form a good dike to quickly stop spills from spreading. That’s why we put PIG Blue Socks in all of our universal spill kits.

An added benefit of vermiculite is that it chemically inert. That means that it doesn’t react with most liquids. It’s also non-biodegradable, which is a requirement for sorbents that will be placed in hazardous waste landfills.

Recycled Newsprint

Socks aren’t always used for big, dramatic spill responses. Sometimes, they just wallow around the bases of machinery, casually soaking up oily leaks and drips. And the recycled newsprint filler in the PIG Super Sock is perfect for the job. Like corncob, recycled newsprint is cellulose – so it’s very absorbent, biodegradable and great for fuels blending.

Recycled newsprint is bulkier than corncob and vermiculite – pound for pound, it soaks up almost twice as much as the other two. It doesn’t hug the floor well enough to form a strong dike like corncob or vermiculite, so it’s not the best choice for spill response.


Polypropylene-filled socks are most commonly used for special applications like hazmat spill response or soaking up oil and not water.

PIG Hazmat Chemical Socks are made of 100% treated polypropylene and have exceptional chemical resistance. They’re the first choice for spill responders who need to contain and clean up hazardous spills without the added danger of having the absorbent react with whatever has been spilled.

PIG Skimmer Socks are filled with untreated polypropylene, so they’ll absorb oil, gasoline, and other petroleum products while repelling water. This makes them great oil absorbents for spills that happen outdoors on both land and water. Because they’re polypropylene, they’re also chemically resistant – which is handy if you’re skimming oils from the tops of acid or caustic baths.

Polypropylene can be treated to absorb water-based liquids, but as sock filler it’s the most expensive option. That means it may be hard to rationalize the added cost if you’re just soaking up an oil leak in the shop. Even though polypropylene socks hug the ground better than those filled with newsprint, you’ll still get a stronger dike with vermiculite. So it’s best to save polypropylene socks for those applications where you really need them.

So take a look around. Make sure the socks you’re using are the right ones for the job because just like people, it’s what’s inside that counts.