Pick what we build next

Balloon hovercraft led the vote, and it's coming in 3 weeks, since it takes a bit to build. For the weekend of Oct 17 we're building polarized stress play: transparent objects between two polarizers.

• Challenge 1

  Cartesian diver

  Sink a diver without touching it

  Squeeze a closed bottle and watch an eyedropper dive and float. Pressure + buoyancy.

  5 votes15%

• Challenge 2

  Instant ice

  Freeze water by pouring it

  Supercooled bottle water turns to ice the moment it hits ice or you slap it. Phase change drama.

  5 votes15%

• Challenge 3

  Milk fireworks

  Make colors explode on milk

  Food coloring dots on milk, then a soap drop — colors race as surface tension collapses.

  5 votes15%

• Challenge 4

  Most votes

  Balloon hovercraft

  Ride a CD on air

  Balloon + old CD + bottle cap = a hovercraft that glides on a cushion of air.

  9 votes26%

• Challenge 5

  Walking-water rainbow

  Make water climb between cups

  Paper towels bridge colored cups; water walks and mixes into a rainbow. Capillary action.

  5 votes15%

• Challenge 6

  Candle in a glass

  Make a candle pull water up

  Light a candle under a jar over a dish of water; when the flame goes out, water climbs. Air, pressure, and cooling — the classic kids demo.

  5 votes15%