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activity: Make a Salt Sculpture

Salt is a crystal that can be nurtured to grow in many different directions and shapes. In 1998, the Exploratorium hosted an exhibition called Turbulent Landscapes, which featured enormous, homegrown salt sculptures by artist Jörg Linzlinger. This activity, created by Jennifer Strick, starts out with a simple approach. But we encourage you to get creative, and see what shapes and colors you can make. Be sure to send in a picture of your creation!

 

CAUTION
Making the salt solution involves heating water to high tempuratures. Kids, please ask an adult to help you with this project.

   
What Do I Need? .

  about 1/4 cup table salt
Did You Know?
There are lots of different kinds of salt found around the world, and some chefs pay a high price for exotic salts like fleur de sel from France, or black lava salt from Hawaii.
  about 1 cup water
  about 3 feet of cotton string
  a small plastic cup or jar that won't melt when hot liquid is poured into it (we used the bottom of a 20-ounce soda bottle, but any container will do)
  a saucepan
food coloring (this is optional; it will color your salt crystals)  
  a tray or plate to hold the cup  
newspapers or paper towels to put under the project  
   
What Do I Do?

 


1.
Cut the string into 6 or 7 pieces, each about 5 inches long, and tie them together at one end so they look like like a string bouquet.

Tip
A sprinkling of salt can take the bitter edge off an acidic tomato or grapefruit.

Share & Discuss
What kinds of shapes could you make with your salt sculptures? Send us a photo!

 

2. To prepare the salt solution, bring the water to a rolling boil in the saucepan. Add the salt and a couple of drops of food coloring (optional). Mix with a spoon to help the salt dissolve. Continue adding salt and mixing until no more salt will dissolve into the water. You should now have a "supersaturated" solution. You might notice a film of salt crystals forming in a layer on the surface of your solution. At this point, turn off the heat and pour the solution into the plastic container.

 

3. Submerge the knotted end of your strings into the solution, and arrange strings evenly so that the ends dangle over and around the rim of your container.

 

4. Leave the container someplace where it's not likely to be disturbed. You might want to put a newspaper or paper towel under it to catch the drippings from the ends of the strings.

 

5. Wait. In a couple of days you should be able to see that your strings have grown fatter from the crystallizing salt. If you continue adding salt solution when it's evaporated below the knot, you should be able to grow long salt stalagmites.

 
 
   
What's Going On? .

When you add salt to water, the crystals dissolve and the salt goes into solution. But you can’t dissolve an infinite amount of salt into a fixed volume of water. When as much salt has been dissolved into a solution as possible, the solution is said to be saturated.

The saturation point is different at different temperatures. The higher the temperature, the more salt that can be held in solution.

When you cook up a batch of salt water, you cook salt, water, and food coloring (if you choose to use it) to an extremely high temperature. At these high temperatures, the salt remains in solution, even though much of the water has boiled away. But when the salt water begins to cool, there is more salt in solution than is normally possible. The solution is said to be supersaturated with salt.

Supersaturation is an unstable state. The salt molecules will begin to crystallize back into a solid at the least provocation. Stirring or jostling of any kind can cause the supersatured salt to begin crystallizing.

 

 

 
What Else Can I Try? .


• You can grow crystals of many sizes and shapes by hanging different lengths of strings at various angles, around or over objects.

• You can make your crystals different colors by adding food coloring. What happens if you mix your first batch one color and then add salt solution of a different color when the first batch has evaporated?

Share your salt sculpture results on our bulletin board!

 
 
 
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