Welcome to PopSci’s at-home science projects series. On weekdays at noon, we’ll be posting new projects that use ingredients you can buy at the grocery store. Show us how it went by tagging your project on social media using #popsciprojects.

When a gray whale swims from Alaska to Mexico in December to start a family, it doesn’t stop for a single meal or snack. Instead, it survives off the foot-thick layer of fat it gains after eating oily krill all summer long. The cache lasts for months, giving the 90,000-pound creature the energy it needs to make the long trek and keep a stable body temperature the entire way.

Lots of animals have fat reserves deep in their bodies, but marine mammals (with the exception of sea otters and polar bears) keep theirs right under the skin to insulate them against ice-cold waters. The tissue, known as blubber, isn’t too different from the shortening you use in pie crusts and cookies. In fact, you can go ahead and experience blubber’s warming powers for yourself by dipping a finger, or two, or 10 into the creamy ingredient. The whole process takes about five minutes, but you’ll probably double that time just trying to scrub the stuff off your hands. Still, the satisfaction for you and the seal pups (read: kids) will be worth it.


  • Time: 10-15 minutes
  • Difficulty: easy

What you’ll need:

Bowl, ice-cube tray, and Crisco shortening
Setup for this project is a cinch. Purbita Saha
  • Vegetable shortening
  • A big bowl you can submerge your hands in
  • A spoon
  • Two trays filled with ice cubes
  • Paper towels
  • Timer


1. Fill your bowl halfway with water and dump in the ice cubes. You’ll want the surface to be pretty icy for that true Arctic feel.

2. Have everyone plunge their hands in to test the temperature. Time how long you can stay submerged for. The water will already be chilly, so you might find it tough to last longer than a few seconds.

3. Cover everyone’s hands in shortening. Use a spoon and spread it evenly so you can really feel the fat’s insulating effect.

4. Take a second plunge into the ice bath. Again, time how long you can stay underwater. You should be able to last 30 seconds or more before the pain and numbness set in.

5. Wipe off the clumps of shortening with a paper towel. This will save you some time when you rinse your hands and also prevent you from clogging up your drain. The shortening will get pretty greasy once you start rubbing it, so apply a generous amount of soap before sudsing up under warm or hot water. A bit of dry sugar can help cut the grease, too.

Spreading shortening on hands
Just like blubber, you’ll want to spread and coat the shortening evenly. Purbita Saha

How it works

Blubber, like shortening, consists of large fat molecules that are hard for heat to pass through (meaning they have low thermal conductivity). So, it traps a lot of the warmth the body produces, similar to a thermos, says Shawn Johnson, vice president of veterinary science and medicine at the Marine Mammal Center in Sausalito, California. If a whale or sea lion dives down to deeper, colder waters, its metabolism will respond by burning more energy to raise its internal temperature. Blubber ensures that all that hard work isn’t lost through simple physical processes like heat transfer.

Fat isn’t the only way animals stay toasty in the ocean. Sea otters and fur seals, for example, catch air between their hairs to create an insulating bubble above the surface of their skin, says Dani Crain, a PhD candidate studying marine mammal anatomy at Baylor University. This is why sea otters are constantly grooming themselves: They’re circulating air through their incredibly dense pelts.

Blubber has many other undersea uses, too. It helps marine mammals retain their shape, whether it be the smooth torpedo likeness of a dolphin or the absolute roundness of a seal. It also provides protection against shark bites, Johnson says, and could have some self-healing properties. And as described with the gray whale, it serves as a rainy-day fund for calories, though we don’t recommend waiting out the pandemic on a shortening-only diet.