Key concepts
Food science

Have you ever wondered how butter is made? How does that creamy spread come from something as liquid as cow's milk? Making butter by hand can be hard work, but it can be easily made at home! In this activity you'll not only get to find out how butter is made, but also how temperature affects the butter-making process. And then you may enjoy the fruits (or rather, toppings) of your labors!

Butter is an ancient prepared food, having been made by people at least 4,000 years ago. Some of the earliest known recipes for making butter call for the use of a container made from animal skin. The skin would be sewed together tightly, leaving a small opening through which to add fatty milk or cream. The vessel would then be suspended, such as from wooden poles, and swung until butter formed. For the last century, however, most butter has been produced in factories.

One traditional butter-making process begins with making cream. When whole milk sits out, tiny fat molecules float to the top, forming a layer of cream that can be skimmed and collected. To make butter, the cream is agitated (stirred up) so that the fat molecules get shaken out of position and clump together. Eventually, after enough agitation, the fat molecules clump so much that butter forms. When this happens, the fat molecules have clearly separated from the liquid in the cream, and this liquid can be removed and made into buttermilk.

• Measuring cup
• One cup of heavy whipping cream
• Cup or glass
• Clean a one-quart glass jar with lid and a tight seal. A canning jar with a lid, seal and ring works best. A different size jar could be used but the amount of heavy whipping cream should be adjusted accordingly.
• Helper (optional)
• Stopwatch or clock
• Bowl
• Cold water
• Small plastic bags

• Pour one-half cup of heavy whipping cream into a cup or glass. Let it sit out at room temperature for about five hours.

• After the one half cup of heavy whipping cream has sat out for five hours, pour it into a clean one quart glass jar. Put the lid on the jar and screw it on tightly.
• For the next step, you may want to get a helper ready to trade off on shaking the jar. It will take several minutes of vigorous shaking to make butter from the cream!
• When you start shaking the jar, start the stopwatch or note what time it is. How does the heavy whipping cream change as you shake the jar? As the cream thickens (within a couple of minutes of when you start shaking), keep shaking the jar!
• Shake the jar until butter forms. This could take between five to 20 minutes. Once you have shaken the jar enough, the liquid will suddenly separate from the butter. The butter will be a pale yellow lump, and the liquid will be milky. You'll probably hear the lump hitting the sides of the jar as you shake it. When the butter and liquid separate, stop shaking the jar and stop the stopwatch.
How long did it take the butter to form when using room-temperature cream? How does the butter and liquid in the jar look?
• Carefully pour the liquid out of the jar. You can store the liquid and use it as buttermilk for other recipes.
• Remove the lump of butter from the jar and place it in a bowl of cold water. Gently knead the butter to remove any extra liquid. Use your fingers to drain the liquid from the bowl. Rinse the butter two more times in this way. (If the liquid is not removed, the butter will go rancid faster.)
• Transfer the butter into a small plastic bag and store it.
• Clean the jar, its lid and the bowl.
• Repeat the entire butter-making process as you just did but this time use one half cup of cold heavy whipping cream straight from the refrigerator (instead of room-temperature heavy whipping cream). Try to shake the jar similarly. How long did it take the butter to form when using the colder cream? How does the butter and liquid in the jar look?
Overall, how long did it take butter to form using the warmer heavy whipping cream compared with the colder cream? Does it look like the temperature affects how quickly the cream turns into butter?
Extra: Repeat this activity a few more times. Do you get similar results each time you use refrigerated heavy whipping cream and each time you use room-temperature cream, or is there variation in your results?
Extra: Weigh the amount of heavy whipping cream that you start with and then weigh the amount of butter that you end with. How much of the cream turned into butter?
Extra: In this activity you investigated how temperature affects turning heavy whipping cream into butter but you did not quantify the temperatures you used. You could repeat this activity, but this time use a thermometer to measure the temperature of the cream when you put it into the glass jar. You could even try some different temperatures of cream and see how that affects the process. How do different temperatures of cream affect the butter-making process?

Observations and results
Did it take a much longer amount of time to make butter using the chilled heavy whipping cream compared with using the room-temperature heavy whipping cream? Aside from this difference, did both butters seem similar?

As you shook each jar, you should have seen and heard the cream initially slosh around, and then gradually the sloshing slowed as the cream thickened. Eventually, after several seconds (but less than two minutes), it should have become so thick that it didn't move much as you shook the jar. At this point the cream had likely turned into whipped cream. After you shook the jar for about five to 20 minutes total, the cream should have abruptly turned into butter. This likely happened much quicker for the room-temperature cream than for the colder cream. (For example, the room-temperature cream may have become butter after five to six minutes, whereas the refrigerated cream took 13 to 15 minutes of shaking.) As the cream is shaken, the fat molecules get out of position and clump together, eventually clumping so much that butter forms. At this point the fat molecules have clearly separated from the liquid in the cream. When molecules are heated, they move faster because they have more energy. Consequently, the molecules in the room-temperature cream moved faster than the ones in the chilled cream, allowing the room-temperature fat molecules to clump together faster, thereby forming butter faster.

You may enjoy some delicious, homemade butter. Be sure to keep it refrigerated and consume it before it becomes rancid.

More to explore
How do you make butter?, from WebExhibits—Butter through the Ages
Making Butter, from Michael Chu at Cooking for Engineers
Rate of Reaction, from Rader's
Shaking for Butter, from Science Buddies

This activity brought to you in partnership with Science Buddies