Can you turn a liquid into a solid by shaking a jar? Yes — and you can eat the result! This experiment turns heavy whipping cream into real butter in about 10–15 minutes, with nothing but a jar and your arms.
What you need
- 1/2 cup (120 ml) of heavy whipping cream — must be cold from the fridge
- A clean glass jar with a tight lid (a 500 ml mason jar works great)
- A pinch of salt (optional, for salted butter)
- A marble or clean coin (optional — speeds things up)
- A colander or strainer and a bowl
- Some bread for tasting!
Steps
- Pour the cold cream into the jar. Add the marble if using. Seal the lid tightly.
- Shake hard — up and down, side to side. Keep going!
- After about 2–3 minutes the cream will turn into whipped cream (thick and fluffy). Keep shaking.
- After 5–10 more minutes you’ll suddenly hear a sloshing sound — a lump of pale yellow butter has formed, swimming in a white liquid.
- Pour the contents through the strainer. The liquid is buttermilk (tasty in pancakes!).
- Rinse the butter lump under cold water, kneading it until the water runs clear.
- Add a pinch of salt if you like, spread on bread, and eat.
What’s happening?
Heavy cream is an emulsion — tiny droplets of fat suspended in water. The fat droplets are coated in proteins that keep them apart from each other, like each droplet having its own bubble wrap.
When you shake the jar, you’re slamming those fat droplets together over and over. Eventually the protein coating breaks, and the fat droplets start clumping together. This is called breaking the emulsion.
Once enough fat clumps together it forms a solid network — butter. The remaining liquid (buttermilk) contains the water, proteins, and a sugar called lactose that couldn’t join the fat.
This is a physical change, not a chemical one. The fat molecules themselves don’t change — they just reorganise from a suspension into a solid. You haven’t made any new substances.
Key vocabulary
- Emulsion — a mixture of two liquids that don’t normally mix (like fat and water), where one is broken into tiny droplets inside the other
- Phase change — a substance moving from one physical state to another (solid, liquid, gas) without changing its chemical identity
- Lipid (fat) — molecules made mostly of carbon and hydrogen; they don’t dissolve in water
- Buttermilk — the liquid left behind when butter forms; slightly tangy and great for baking
- Physical change — a change in shape, state, or arrangement, but not in chemical identity
Math connections
You started with 120 ml of cream. Butter is roughly 80% fat — the rest was water and proteins that left in the buttermilk.
- If you got about 60 g of butter, how much of that is fat? → 60 × 0.8 = 48 g
- The buttermilk you strained off had the other 20% of solids plus the water. Can you estimate how many ml of buttermilk you collected? (Hint: 120 ml of cream minus the butter volume.)