Charcoal crystals uses evaporation to grow the crystals, which will continue to grow for weeks afterward.  You’ll need a piece of very porous material, such as a charcoal briquette, sponge, or similar object to absorb the solution and grow your crystals as the liquid evaporates.  These crystals are NOT for eating, so be sure to keep your growing garden away from young children and pets! This project is exclusively for advanced students, as it more involves toxic chemicals than just salt and sugar.

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The materials you will need for this project:

  • Charcoal Briquettes (or pieces of sponge or brick or porous rock)
  • Distilled Water
  • Uniodized Salt
  • Ammonia (Keep this out of reach of children!)
  • Laundry Bluing
  • Food Coloring (optional)
  • Pie Plate (glass or tin)
  • Measuring Spoons
  • Disposable Cup
  • Popsicle Stick

Download worksheet and exercises

The first thing you’ll need to whip up a batch of solution, then you’ll start growing your garden.  Here’s how you do it:

1. Into a disposable cup, stir together (use a popsicle stick to mix it up, not your good silverware) 1 cup of water, 1 tablespoon of ammonia, 1/2 cup of laundry bluing, and 1/2 cup of salt (non-iodized).

2. Place your charcoal or sponge in a pie tin and pour your solution from step 1 over it.

3. Wait impatiently for a few days to one week.  As the liquid evaporates, the salts are left behind, forming your crystals.

4. Continue to add more solution (to replace the evaporated solution) to keep your crystals growing.  Think of it as ‘watering’ (with your special solution) your crystals, which are growing in your ‘soil’ (sponge).

5. You can dot the sponge with drops of food coloring to grow different colors in your garden.

Questions to Consider…

Why do you think you needed ammonia and ‘laundry bluing’ for this experiment?  What is ‘laundry bluing’, anyway?  Why do the crystals form just on the porous object and not the glass/metal pie plate?   Let us know in the comment field below what you think:


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