Make Potato Oobleck in 6 Steps

In this non-Newtonian science experiment, watch potato separate into water and a starch goo that turns solid when squeezed.

 

Materials you'll need

• 5–6 potatoes
• knife and cutting board (with adult help)
• blender
• large mixing bowl
• warm water
• spoon or spatula
• fine mesh strainer
• clear glass bowl

 

Step-by-step tutorial

Step 1: Wash 5–6 potatoes and, with adult help, chop them into chunks. You can leave the skins on.

Step 2: Blend the chunks until they turn into a thick, shredded pulp, then scoop the pulp into a large mixing bowl.

Step 3: Pour warm water over the pulp and stir it around. Use warm water, not hot, or the starch will turn into paste instead of loose grains. Watch the water turn cloudy and brown as starch washes out of the potato.

Step 4: Set a fine mesh strainer over a clear glass bowl and pour the potato mixture through it. The cloudy liquid goes into the bowl and the chunky pulp stays behind in the strainer.

Step 5: Let the liquid sit for 10 minutes without touching it. A white layer will slowly build up on the bottom of the bowl.

Step 6: Carefully tip the bowl and pour off the brown liquid on top, leaving the white layer behind. Scoop up the goo and squeeze it in your hand, then open your fingers and let it drip.

Learn more

Every potato cell is stuffed with tiny grains of starch. Blending smashes those cells open so the grains float loose in the water, and the strainer then holds back the chunky fiber while letting the starch through. Starch grains are denser than water, so after ten minutes of sitting still they sink and settle into a white layer at the bottom of the bowl. Pour off the water on top and what's left is a non-Newtonian fluid, a mix that acts like a liquid one second and a solid the next. Squeeze it fast and the grains push against each other into a lump you can hold. Open your hand and they slide apart again and it drips right through your fingers.

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