Ice cream science: Make a cool treat to beat the summer heat

It’s getting to that time of year when it’s so hot and yucky outside that everything cold is better.

It’s also a time for telling kids about how, when you were their age, if you wanted ice cream you had to turn a crank until your arms fell off (presumably while walking uphill to school both ways and fighting off bears…).


Here in the Houston Museum of Natural Science education department, we have tried making ice cream in a variety of ways to see what is easiest for kids, and not all ways are equal. (Pro tip: Those special ice cream-making balls they sell for kids freeze shut, and then kids are sad. Not recommended.) Our favorite way, at the end of this post, is fairly cheap and easy and fun for kids, but before we get to the instructions, let’s talk about some science.

To make ice cream, you will of course need ice. The ice is simply to lower the temperature of the cream to the freezing point, but if you just used ice alone and let it sit, you’d end up with a solid block of cream – more like an ice cube – and it would take longer to freeze. What makes ice cream special is salt and stirring.


Water freezes at 32° F, but sprinkling salt on the ice lowers the freezing/melting point of water. How, you say? In order for liquid water to freeze to solid ice, all of the water molecules have to slow down enough to connect to each other and form solid crystals. When this happens, the water loses kinetic energy due to the decrease in movement of those molecules. Because temperature is a measurement of kinetic energy, this results in a lower temperature.

The presence of salt interferes with this process. The water molecules can’t attract each other as easily because they are also attracted to the sodium and chloride ions from the salt. Mixing the salt, ice, and water together results in a temperature below the freezing point of water, which helps the cream freeze faster. The shaking or stirring helps cool the cream evenly and efficiently. In ice cream, this lower freezing point turns the fats into solids, but the water content to be almost frozen.


What about the milk, then? It is much easier to make ice cream with creamer, heavy whipping cream, or half-and-half than to use skim milk because of the higher fat content in cream. You can make ice cream with skim milk, but it is really, really, really hard to do by hand, AND you have already committed to making ice cream, so I feel like you have acknowledged the inherent risk of fat consumption that comes with making a frozen confectionery delight. Just use the full-fat stuff, and let’s all move on.

What does the fat do, anyway? Primarily the higher fat content allows for a richer, creamier texture and a more delicious flavor in your finished product. The reason for this is that when you are cooling and mixing the cream, you are also introducing air molecules to the liquid. The bits of fat in the cream add a little structure to the ice cream and trap these air molecules in the solution as it forms. This, plus the lower freezing temperature, enables you to be able to scoop the ice cream fairly easily because it allows for there to be a bit of unfrozen water in the ice cream, which stops the ice cream from becoming a solid block of ice.


If you have ever had ice cream that has grown ice crystals and gotten a bit of freezer burn, those ice crystals appeared because the unfrozen water in the ice cream had a chance to migrate a little bit when the ice cream was warmed slightly on the ride home or when it was left on a counter a little too long and then frozen again. There are things called stabilizers added to your ice cream to prevent this from happening. Most ice creams today have one of five stabilizers added to them: carob bean gum* (a type of bean from Africa), carrageenan (a type of algae), guar gum (a type of legume from India), sodium alginate (made from seaweed) or carboxymethyl cellulose (sounds scary but it’s plant-based). Often, if you read the label, you will see more than one of these in your ice cream to keep it smooth and delicious.


* Carob beans, or locust beans, are cool. They are from exotic African trees and each bean is so similar that at one point they were used as a unit of measurement for gold and silver. We still use this measurement today, but the name has changed over time to Karat.

So now that you have had a little lecture about the science of ice cream, let’s get to the delicious lab work.


Activity: ICE CREAM!!!!


Individual serving containers of coffee creamer


Small waterproof container or quality sealable plastic sack big enough for about two or three cups of chipped ice

Salt, any variety

A dish towel to insulate your hands

Optional: Inexhaustible energy of small child-based labor



  1. Find some liquid coffee creamers in individual pots.
  2. Put ice in your water proof container, filling it about a third of the way. Smaller chunks of ice work better because there is more surface area, but any ice will do.
  3. Layer your salt on your ice. Several solid sprinkles will do, but if you are nervous about the quantity, add some extra just in case. It won’t hurt anything.
  4. Put your sealed creamer cup(s) in your container and then put more ice in, filling it about 2/3 of the way.
  5. Layer on more salt.
  6. Finish filling the container with ice.
  7. Start shaking your container. Make sure it is well sealed and that you have a firm grip on it. No one wants to be injured in an ice cream-related accident. There is no way to spin that so it sounds cool. Also, this is an excellent job for kids to help with. Put on a nice, long song or two and let them wiggle till they drop. About ten minutes will do it, but you will know when you are getting close because a frost will form on the outside of your container. If you don’t feel frost forming after a couple of minutes, add more salt. To speed this process up, start with creamer pods that have been stored in the fridge. This way, your creamer will start at about 50° F, and you won’t have to work so hard.
  8. After about 10 minutes of shake, shake, shaking your ice cream, dig your creamer cup out of the ice and wipe it off.
  9. Ta dah! You are done. Unless you want to make this tablespoon of delicious homemade ice cream into a sundae and add chocolate and banana or some jelly for more flavor.


Note: If you are thinking to yourself, “That seems like a lot of work for a tablespoon of ice cream,” well… it is. But it’s also science. So there.

If you get the liquid creamer that comes in a larger container at the grocery store, you can increase the volume of your creamer and make MORE ice cream. If you choose to do this, you will need to find a small waterproof (and I would suggest plastic) container to pour the creamer into and then a slightly larger waterproof container for all the ice and the salt. It’s the same procedure, just with a larger amount of the ingredients!



The Things I Made at Summer Camp

Xplorations Summer Camp has been an integral part of summer at the Houston Museum of Natural Science for decades, and it was a large part of my childhood too. Over the years, I took all sorts of camps covering subjects like butterflies, cultures in the Americas and roller coasters. I made so many things at camp that I could probably have an entire exhibit called “Things I Made at Camp!” However, like fossils and artifacts, not all of my camp collection has survived to the present day. I wanted to see which items survived the decade since their creation, so I went on an excavation in my childhood home to uncover some of the lost artifacts.

First stop, my childhood bedroom. Among the stuffed animals and children’s books, I find many remnants of my childhood. Papers from school, photos from birthday parties, but no sign of Xplorations Summer Camp. Then, in the distance, I spot a woven basket. The woven basket (ca. June 1997) was made in a camp covering the cultures in the Americas. While I toiled weaving the reeds in and out, we talked about how many cultures wove baskets to hold food and water. To be honest, this woven basket is not my best work. It could certainly not hold water, and there aren’t many foods that can fit inside. In fact, it has a very distinct lean. It looks like it shares some characteristics with a cornucopia.

20150530_162901Onwards! As I search through my desk, I find the remnants of my emergency kit (ca. 2001) made in Survivor Camp. The original kit was encased in a convenient fanny pack, but the fanny pack has since vanished. All that remains is an emergency blanket, glow stick, and some matches in a waterproof container. If need be, I can survive a cold, dark evening with only these three supplies and the skills I remember from camp. I do miss the fanny pack though. Now that was survival and convenience all in one.


My search continues. I have combed through all of the things in my room, and in a last-ditch effort I turn my search to the closet. Attached to my navy JanSport backpack, I find a handmade bead animal (ca. 1999). I was an after-camp kid, so I got the chance to make some fun crafts like bead animals after we finished the normal camp day. This particular bead animal was very special because of the rare sparkle blue pony beads that were used for the eyes. In the after camp world, those beads were a prized commodity.


Eventually, I realize that my search has run cold. There are no more camp crafts to be found. I remember how some of them have been lost. In a medieval camp, I made potpourri and planned to give it to my dad for Father’s Day. Unfortunately, I was a clumsy kid and dropped the glass jar of potpourri on the floor. It did not make it home from camp. I’m sure a number of other camp crafts were dropped in puddles, broken in backpacks, or simply left behind. For all of those lost camp crafts, there are a number of memories that stay with me. As summer camp 2015 commences, I like to think that new campers will make some memorable camp crafts too! Let’s hope that they all make it home!


Editor’s note: HMNS is in its first week of Xplorations Summer Camp right now! Registration is open to children ages 6 to 12. Camp runs Monday through Friday from 10 a.m. to 3 p.m., and care is available before camp from 8 to 10 a.m. and after camp from 3 to 5:30 p.m. for an additional fee. Live near Sugar Land? Register for camp at our sister location, HMNS Sugar Land. Be a part of the tradition at HMNS Xplorations Summer Camp, and like Kelsey, let your child learn and build lasting memories at the museum.

School’s (almost) out for summer: Time to xplore with our Xplorations Summer Camps!

Summer Camp is here again!  As we busily prepare, buying all the weird odds and ends it takes to run camp here (everything from plastic spoons to sheep eyeballs), I thought I would share a bit about camp with you.

Xplorations Summer Camp 14Recently I gave a presentation to fellow HMNS staff members about Xplorations Summer Camp, just a little informal FYI. I was surprised at how many of them stopped me later in the day and said, “I didn’t know that ­­­­­­­­­­­­­­­_________.” 

The No. 1 item they commented on was the sheer size of our summer camps. We have approximately 550 campers per week at HMNS in Hermann Park. This means that, according to the National Center for Education Statistics, we are larger than your average elementary school each week for the eight weeks of camp. 

Because of this, we take safety very seriously … which brings us to the second most surprising camp fact I shared: Staffers were also amazed to learn that all the full-time Youth Education Programs staff regularly has First-Aid, Epi-Pen injection, and Heart Saver/AED training. We have found that parents really like getting their campers back in the afternoon in same condition as when they signed them in in the morning. To that end, we feel like we should be prepared for a whole range of potential problems — everything from a Band-Aid solve-able boo-boo to a zombie apocalypse.

Our number one goal is to keep our campers safe!  A close second is to have fun while learning.

And because we are always learning new things around here, I learned how to make this infographic with some of the other numbers and statistics our staff found interesting about Xplorations Summer Camp. 

Summer Camp InfographicIf you haven’t signed up your little scientists, you’d better do it quickly.  Spots are vanishing before our eyes! 

Camp is an excellent, hands-on way to introduce kids to topics in science. They learn, have fun and are able to explore themes and careers that can help them change the world. Perfect for kids age 6-12, sign up for Xplorations Summer Camps today! Click here to see our full catalog of age-specific camps.

Educator How-To: Mimicking weather with convection currents

There has been a lot of strange weather this spring. Temperatures in North Dakota reached -60°F — which is about the same temperature at the surface of Mars, and about 50°F colder than the North Pole on the same day. 

Meanwhile, in Australia, temperatures reached over 120°F! California is at its driest point since they started keeping records in 1849. And just recently, a bout of deadly tornadoes tore through the Midwest.

The rapid changes happening on the surface of the Earth, like hurricanes and tornadoes, and the slower changes happening under the Earth’s surface, like earthquakes and volcanoes, are as awe-inspiring as they can be terrifying.  Understanding the dynamic Earth helps us prepare for the worst that Mother Nature has to offer.

On that note, here’s a simple but really cool experiment you can do to get you started on the path to meteorology mastery. With a few simple items, you, too, can create a convection current.

Activity: Convection Currents

-Large, clear container with a depth of at least two inches (a Pyrex loaf pan would work)
-Red and blue food coloring
-Ice cube tray and access to a freezer
-Electric kettle, stove or microwave to boil water
-Styrofoam cup to hold very hot water


  1. Dye water blue using food coloring (make it pretty dark). Then freeze in an ice cube tray. When you have your ice cubes made, move on to the remaining steps.
  2. Begin to heat water in an electric kettle. You’ll use it later on.
  3. Fill a clear container with tap water, and then set it on the table to settle. The water should be as still as possible, so try not to jostle the table.
  4. Carefully place a blue ice cube at one edge of the clear container. The blue ice makes it easier to see what happens to the cold water melting off of the cube. You should notice where the cold blue water goes in the clear container.  View the container from the side — your eyes should be about the same height as the water.
  5. Repeat this process again to make sure it isn’t a fluke! (It’s not…)
  6. The cold water tends to sink down. (It is denser — heavier for its size — than the room temperature water). So what do you expect warm water to do if we added some to the bowl? Let’s find out.
  7. Add several drops of red food coloring to the bottom of the plastic or Styrofoam cup. Pour approximately half a cup of heated water into the cup. Lower the cup close to the surface of the water near one edge of your demo tank, and pour a small amount of the hot red water into the tank. Try to pour it so it runs down the side of the container and try to disturb the water as little as possible.
  8. Does the red water do what you expected?

What’s Going On Here?

So how does this relate to the weather? Well, it’s all about convection!

Convection is the action of warm air rising and cold air sinking. You are using water to model some things that also happen in the atmosphere because sometimes air moves in similar ways to water. You probably guessed that the blue water represents a cold air mass and the red water represents the warm, unstable air mass.

A thunderstorm is caused by unstable air and convection plays an important part. A body of warm air is forced to rise by an approaching cold front. Other things can cause warm air to rise, like a mountain slope. In this experiment, the cold water sinks while the warmer red water rises, or stays higher than the blue.

Can’t get enough of the science of weather and natural disasters?  We’ve got four things to quench your thirst for all things weather!

1. In a new special exhibit open this summer, Nature Unleashed: Inside Natural Disasters, you will come face-to-face with the inside of a tornado, create your own volcano and earthquake, and witness the aftermath of several historical disasters. You’ll see why these events happen and how we study to better predict them.

2. On the lower level of the Museum, you can step in front of the camera and join KHOU Channel 11 News Meteorologist Chita Johnson for a severe weather update — with you as the weather reporter! It’s lights, camera, action! as you become the star of the show on a replica of the Channel 11 weather set!

3. Are you ready for nature’s fury? Force 5 in the Planetarium is your chance to survive three Category 5 storms — a hurricane, a tornado and a solar eruption — without any rain, wind or dangerous radiation. Discover the causes of weather catastrophes and venture into the middle of the action when nature goes Force 5!

4. For the smaller scientist in your family, check out Calamity Camp for 6 and 7 year olds and Nature Unleashed for 8 and 9 year olds. In Calamity Camp, you will tame a twister, battle a blizzard, hunt a hurricane and much more as you explore and experiment to discover nature’s awe-inspiring fury. Nature Unleashed is an exciting interactive journey to the center of the Earth, where we’ll explore earthquakes, volcanoes, tsunamis and more!

No matter how you explore weather at HMNS this summer, you’ll be blown away!