My husband made butter in a baby food jar as a child and it must have made a strong impression, because he’s been saying we should do this for YEARS. (I think even before we had kids.) Well, we finally did it and I can attest that it was just as easy and satisfying (and delicious) as he said it would be. All you need is a small leak-proof container, like a baby food jar, some heavy whipping cream, and a bit of endurance.
This butter-making project was actually way more fascinating than I thought it would be. When we started shaking our little container of cream, first it started to get a little frothy, which wasn’t very surprising. However, before we knew it, the jar which was initially only half-filled with liquid cream was now nearly entirely filled with whipped cream. After shaking it a little more, the whipped cream turned into a somewhat unappetizing chunky substance. After a couple more minutes of shaking, we had a ball of solid butter bouncing around inside a jar of liquid buttermilk.
How does it work? First I’ll give you a quick and dirty, extra simple rundown on the process in case you have curious young kiddos. For those of you more technically-inclined or with older kids, I’ll follow up with a little more rigorous, terminology-filled explanation of the science of butter.
To explain it simply, I would tell a child that the cream that we started with is actually a mixture of tiny little bits of fat (way too tiny to see) inside a watery solution (you could just say water, but there is technically also some other stuff like sugar mixed in). When we shake up the cream, the little tiny pieces of fat get broken up. Since fat and water don’t mix well, the fat would rather be close to air than water, so little tiny air pockets form and are held together by the fat particles. Since the cream is now mixed with air, the whipped cream takes up more space (volume) than the liquid we started with. If we keep shaking up the container, eventually the air pockets pop and the little bits of fat find each other, leading to a big lump of butter surrounded by the watery solution we call buttermilk.
If you’re even more curious or your child is older, you could also use this project as a way to explain colloids. Scientists are a little persnickety about their jargon, but solutions, colloids, and suspensions are all very similar in that they are all types of mixtures between two things. If the dispersed substance is extremely small to the point that it is dissolved in the medium (like sugar in water), we call this a solution. Solutions are frequently clear. If the dispersed substance is relatively large and will eventually separate into different layers if left alone (like sand in water), we call it a suspension. If the particle size is somewhere in the middle (1 to 1000 nanometers if you want to be precise) we call this a colloid. Colloids are frequently opaque (like milk or cream) and it is not easy to filter out the dispersed substance from the medium (also called the continuous phase).
In this activity, the heavy whipping cream, the whipped cream, the butter, and even the buttermilk are all considered colloids. An emulsion is a type of colloid that is a mixture of two or more liquids that don’t normally mix. The heavy whipping cream and the buttermilk are both emulsions in which the dispersed phase is milk fat and the continuous phase is a water-based solution. The fat content in the buttermilk is much lower than that of the heavy cream. The butter is also an emulsion, but in this case the milk fat is the continuous phase with small amounts of water dispersed throughout. The whipped cream is a special type of colloid called a foam, since in this case, the dispersed medium is air. If you would like a more thorough, molecular approach to the science of butter, I highly recommend this article called Cream Science: On Whipping, Butter, and Beyond by seriouseats.com.
Recommended Age Range: Preschool, Kindergarten, Elementary, Middle School, High School
Time Required: ~15 minutes
Difficulty: Easy (though a little tiring)
Cost: A couple dollars for the heavy cream, though we didn’t use it all.
- heavy whipping cream (enough to fill your jar halfway)
- salt (optional – It might not last long without salt, but ours didn’t last long anyway, because we ate it.)
Supplies & Tools:
- baby food jar (or other small leak-proof container)
- Fill container halfway with heavy whipping cream.
- Shake! (We’ve found it can take anywhere from 5 to 15 minutes depending on the vigorousness and endurance of the shaker, but you’ll know when you’re done, because the butter and buttermilk will separate leaving a lump of butter in your jar.)
- Pour out the buttermilk (or save to use in pancakes!)
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