Grow salt crystals at home

• Table salt 
• Hot water (not boiling) 
• A clean glass or jar 
• A spoon 
• Cotton string or wool 
• A pencil or a clean lolly stick 
• A paper clip or small weight (optional) 
• Food colouring (optional)

• Ask an adult for help with hot water. 
• Do not drink the salt solution. 
• Wash your hands after the experiment. 
• Keep away from small children and pets.

1) Make a salt solution

• Carefully fill your glass halfway with hot water.
• Slowly stir in the salt (add only one spoonful at a time).
• Keep adding salt until no more will dissolve. Some salt should remain at the bottom. This is known as a saturated solution.

Fun Fact:

A saturated solution contains the maximum amount of dissolved salt that the water can hold.

Optional 2) Prepare your crystal seed

• Tie one end of the string around a pencil.
• Let the string hang into the middle of the glass without touching the sides or bottom.
• If needed, tie a paper clip to the end to keep it straight.

Fun fact: 

This step is not necessary, as crystal growth can begin on the walls of the glass. This is known as heterogeneous nucleation, where crystals start to form on a surface or interface rather than appearing spontaneously within the solution.  However, this step will aid crystal growth. 

3) Wait

• Place your jar somewhere it won't be disturbed.
•  Wait and watch your crystals grow. 

You may start seeing crystals within a day, but larger crystals usually take several days.

4) Observe your crystal

• Look closely every day.

Can you answer these questions?

• What day did crystals first appear? 
• Where did you notice crystal growth first?
• How large did the crystals grow? 
• Did they all have the same shape? 

Try changing just one thing each time.

• Warm room vs cool room 
• Thin string vs thick string 
• Different amounts of salt 
• Add food colouring 
• Cover the jar loosely vs leave it open
• Try growing sugar crystals 

Note down all your observations! 

Which experiment grows the biggest crystal?

Salt is made of tiny particles that are far too small to see. When salt is added to water, these particles separate into charged particles called ions. The water molecules surround the ions and help keep them dissolved and spread throughout the solution.

As the water slowly evaporates, the amount of water in the solution decreases, but the dissolved salt remains. This causes the salt concentration to increase. Eventually, the solution becomes supersaturated, meaning it contains more dissolved salt than it can remain stable.

At this point, the dissolved salt ions begin to come together. Small groups of ions may form, creating tiny starting points for crystal growth. This process is called nucleation. In this experiment, nucleation may occur on the walls or bottom of the glass. When crystals begin forming on a surface, this is known as heterogeneous nucleation.

Once a stable crystal has formed, more salt ions can attach to its surface. The ions arrange themselves in a regular, repeating pattern called a crystal lattice. This ordered structure gives salt crystals their characteristic cubic shape.

As more ions attach to the crystal, it gradually grows larger. This process is called crystal growth. The overall process of forming and growing crystals is known as crystallisation.

The speed and shape of crystal growth can be affected by factors such as temperature, evaporation rate, salt concentration, and whether the solution is disturbed. This is why crystals grown under different conditions may look different.

Scientists study processes such as nucleation and crystal growth to understand and control the properties of crystals. This is important in areas including pharmaceuticals, agriculture, batteries and advanced materials.

Growing crystals at home is just the beginning.

At CrystoGen, we develop software that helps scientists understand how crystals grow before they even enter the lab. Our simulations support research across pharmaceuticals, advanced materials, batteries and many other industries.

Every crystal starts small... and so does every scientist.

We'd love to see and share what you've grown, so send pictures of your crystals to us at team@crystogen.org!