Grow ‘em big!

Obtain marvelous crystals at home!

2 days



  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
  • Observe safety precautions when working with boiling water.
General safety rules
  • Do not allow chemicals to come into contact with the eyes or mouth.
  • Keep young children, animals and those not wearing eye protection away from the experimental area.
  • Store this experimental set out of reach of children under 12 years of age.
  • Clean all equipment after use.
  • Make sure that all containers are fully closed and properly stored after use.
  • Ensure that all empty containers are disposed of properly.
  • Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
  • Do not replace foodstuffs in original container. Dispose of immediately.
General first aid information
  • In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
  • If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
  • In case of inhalation: Remove person to fresh air.
  • In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
  • In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
  • In case of injury always seek medical advice.
Advice for supervising adults
  • The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
  • This experimental set is for use only by children over 12 years.
  • Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
  • The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
  • The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
  • Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.

FAQ and troubleshooting

The CuSO4 isn’t dissolving. What should I do?

Copper sulfate may not dissolve completely in these conditions, so just pour the solution into a Petri dish, leaving the insoluble precipitate behind.

The copper sulfate didn’t dissolve completely, and when I poured the solution into the Petri dish, I poured the sediment out with it. What should I do?

In this case, transfer the solution back into the disposable cup and rinse the Petri dish with water. Carefully pour the solution back into the Petri dish, this time without the sediment.

The crystals are growing very slowly or aren’t growing at all.

Wait just a little longer — you’ll get your beautiful crystals in the end! Crystals take longer to grow in isolated places, but they’ll eventually grow much larger and will have fewer defects.

My crystals turned out small and rather unimpressive.

This can happen if some dust gets into the solution or the forming crystals are exposed to a temperature change.

But all is not lost! Wait until the crystals are completely formed. Dissolve the same crystals in 20 mL of boiling water and pour the solution back into the Petri dish. Try to shelter the solution from dust and changes in temperature.

How can I preserve my crystals?

If you want to keep your crystals nice, coat them with a colorless nail polish. After the nail polish dries, store the crystals in a closed container.

Step-by-step instructions

Dissolve some crushed crystals in hot water.


Pour the solution into a Petri dish to let it dry.


As the water evaporates, crystals start to form and grow larger, until all the liquid water is gone.



Please refer to local regulations when disposing of chemicals. Dispose of other solid waste with household garbage. Pour leftover solutions down the sink. Wash with an excess of water.

Scientific description

The crystals you obtained are virtually identical to a naturally-occurring mineral called "chalcanthite," which is also a form of copper sulfate CuSO4. It's not exactly common in nature, and you may have already guessed why: copper sulfate is readily soluble in water, and there are not many places on Earth both rich in copper and constantly dry enough for the crystals to stay intact.

To preserve the water-soluble crystals, mineral collectors keep them sheltered from high humidity. You can do this too! Or you can simply coat your crystals with a transparent varnish to prevent water damage.

By the way, copper sulfate is not the only substance that can form crystals in the experiment conditions. Follow the same steps with K3[Fe(CN)6—and watch as blood-red crystals grow in the Petri dish!