By Eric Fowler
Years ago, after shelling out a few bucks for another bag of ice while on a fishing trip in the Sandhills, a friend of mine gave me some sage advice that has stuck with me: “I can make that stuff for next to nothing.”
Since my bloodlines include some frugal genes, I’ve been making block ice in the freezer using various sizes of plastic containers ever since, and smashing it into bits with a hammer when I need cubes.
I also have some nerd genes in me, so I’ve often questioned the science behind ice, coolers and keeping stuff in them cold. There are plenty of tips online, but are they fact or old wives’ tales? Having forgotten most of what I learned about thermodynamics in high school and college physics classes, I asked an expert on the subject: Dr. Christian Binek, a physics professor at the University of Nebraska – Lincoln.
Block or Cube?
You used to be able to buy blocks wherever ice was sold, but I can’t tell you the last time I’ve seen it for sale. It seems to last longer, but does it?
Indeed it does, Binek says, due to the increased surface area of cubed ice compared to a block weighing just as much. There is a misconception about cooling. It’s not that cold goes into something. Rather, it is that heat flows. This flow of heat is called the current entity, and the temperature difference between what you are keeping cool and the ice determines the magnitude of the current.
“If you have smaller cubes of ice, or crushed ice, then you significantly increase the surface area it can flow through, and then the heat transport is just more efficient, or faster,” Binek says.
This is the type of science Binek studies at the Voelte-Keegan Nanoscience Research Center where he works. They look at things on a nanoscale, where the number of atoms on the surface of a particle can be greater than the atoms within it. Ice melts quickly at that scale.
All that said, block ice isn’t always the best way to go. “Let’s say you put your beer in the cooler, but the beer was not initially cold. Crushed ice would be an advantage because it will cool it faster,” Binek said. “But if your beer was cold and your goal is to keep it cold longer, then it might be a good idea to go with a solid block.”
To Drain or Not to Drain?
So what about the water that begins to pool in the bottom of the cooler as the ice melts? I’ve read or heard both sides of the cooler soup story.
“Water, as you say in the language of thermodynamics, has a high heat capacity,” Binek says, adding that property is what makes it an ideal fire extinguisher.
Water can also take on three forms, depending on the temperature: solid, liquid and vapor. During the transition between those phases, the temperature does not change.
“Let’s say you have ice, and that ice is pretty much at 0 degrees Celsius, or 32 degrees Fahrenheit. Then you feed in heat, and the ice starts to melt. Until the last piece of ice is gone the temperature hasn’t changed a bit, not at all. It always stays at 32 Fahrenheit.
“Basically, if you drain it out, you waste that potential to keep stuff cool.”
So leave the water unless you have a ready source of ice. A cooler holding a sandwich or other food, however, is another story. “It’s just nasty to have water floating around and making things soggy,” Binek says.
Dead Air?
Another popular theory is that filling the airspace in a cooler increases ice retention. In reality, air is the second-best insulator there is, trailing only a vacuum, Binek says. It is actually what makes the insulation we use in our homes, and coolers, work, not the materials those insulations are made with. “Air has little material, so it has a tendency not to transfer heat very well,” Binek says.
“Now, what makes air bad for your cooler is simply when you open and close your cooler and the air escapes, or a large fraction of it will, and you exchange the cold air with air from the outside. That, of course, is bad because you bring in heat.”
Filling pockets to limit that exchange has value, Binek said, as does keeping the cooler closed. “Practically speaking, what’s the good of the cooler if you cannot open it?”
Super Coolers?
High-dollar, thick-walled coolers, some seeming to weigh as much as the beverages you could fill them with, have been the rage for some time now. Are they worth it? That depends, Binek said.
“Let’s say you go fishing in a more remote area, and you are off the grid and off access to ice or whatever for multiple days. Then, it is a very valid investment,” he said. “You can keep your beer literally passively cold for multiple days, up to a week, if you have a very expensive cooler. But if you’re just sitting at a lake for a couple of hours, then it’s overkill.”
For now, Binek, a native of Germany, keeps his trips to the lake simple, his small, standard-issue cooler filled with cubed ice and a few beers he can sip while waiting for a catfish to bite.
“Contrary to a far-reaching myth, Germans do not drink warm beer,” he said. “And honestly, I have the impression that if you don’t have a beer, they just don’t want to bite. I don’t know why that is. Maybe you are more relaxed then, and somehow it goes through the rod and through the bobber. Or maybe it’s the hops that gives you more patience, because fishing can have something to do with patience.”
Either way, he doesn’t need a super cooler. “My beer is usually gone before it has a chance to get warm.”
Ice and Coolers
Here are some tips for making ice and making it last longer.
- When making block ice, know that thin plastic containers can crack as water freezes and expands. But don’t use your wife’s best Rubbermaid to make block ice, as it can damage the inner coating.
- Throw what’s left of your block ice back in the freezer when you get back from a trip to use on the next one.
- If you will be far from an ice vendor and have cargo space, fill a quality cooler with block ice you can transfer to other coolers as needed.
- Keep your cooler out of the sun and your ice will last much longer.
- Precool everything in the refrigerator before you put them in the cooler. Freeze some of your water bottles and use them as ice. They will be partly thawed by the time you need them.
- If you store your cooler in a hot garage, bring it inside the day before your trip and it won’t eat some of your ice when you fill it.
- Coolers are just as good at carrying empty bottles and cans home as they are at carrying full ones to the lake. Leave no trace.