Make a salt sculpture

Make a salt sculpture

Be creative in the science kitchen

Make a salt sculpture...

We've showed you how to make a soap sculpture. Now, we'll show you how to make a salt sculpture!

What you need:

  • Around 1/4 cup table salt
  • Around 1 cup water
  • Cotton string
  • Small cup or jar - one that won't melt when hot liquid is poured into it
  • Saucepan
  • Food colouring - the colour is up to you!
  • Newspaper

How to:

Ask an adult for help with boiling water.

  1. Cut the string into pieces around 10cm long. Tie them together at one end.
  2. Boil the water in the saucepan. Add the salt and a couple of drops of food colouring. Stir until the salt dissolves.
  3. Continue adding salt and stirring until no more salt will dissolve.
  4. Pour the salt solution into the cup or jar.
  5. Put the knotted end of your strings into the solution. Arrange the ends of the strings evenly so they dangle over the edge of the container.
  6. Leave the container somewhere it won't be disturbed. Put newspaper underneath to catch any drips from the strings.
  7. In a couple of days you should start seeing crystals forming. If you keep adding salt solution once the original solution has evaporated below the knot you can grow really long salt crystals.

Try growing different sizes of crystals by using different lengths and widths of string. You could use different food colourings and make a rainbow salt crystal.

Take a look at this time-lapse video of salt crystals forming. In the video, no string is used. The crystals form on the rim of the container.

How does it work?

When you add salt to water, the crystals dissolve and form a salt solution. When as much salt is dissolved in a solution as possible, the solution is saturated. The saturation point is different at different temperatures. At higher temperatures, more salt can be added to the solution.

When you heated the water, you could add lots of salt - the saturation point is high. When the salt water begins to cool, there solution is supersaturated. There is more salt in the solution than is normally possible at low temperatures. Salt molecules begin to crystallise out of the solution back into a solid.