A crystal garden is a simple, fun experiment that you can do at home with a few basic ingredients. Most experiments use liquid bluing, also known as laundry bluing or simply bluing, but if you don’t have any, you can still create your crystals. You can either substitute the liquid bluing or carry out another type of crystal experiment.
TL;DR (Too Long; Didn't Read)
The easiest way to make a crystal garden is with liquid bluing, but if you don't have any, you can use powdered bluing or make your own Prussian blue suspension.
Liquid Bluing in Crystal Experiments
The reason people use liquid bluing in crystal experiments is to make the crystal bloom into broccoli-like shapes like trees in a real garden, rather than chunks or plates. Bluing solution consists mainly of ferric ferrocyanide (commonly known as Prussian blue) and water. The Prussian blue doesn’t dissolve in the water, so it remains suspended in the liquid. This is a colloidal suspension.
At the start of a crystal garden experiment, you mix liquid bluing with salt, water and ammonia to create a watery blue sludge. Pour it over small pieces of porous material, like sponges and clay pot pieces, in a plastic container. Leave the container overnight, and by the next day, crystals should form. You keep the "garden" growing by adding more salt and more of the sludge mixture. As the water and ammonia evaporates away, the collodial particles provide seeds for the salt to produce crystals, creating the broccoli shapes.
Alternatives to Liquid Bluing
If you don't have commercial liquid bluing, you can substitute powdered bluing, if you mix it with distilled water in a 1-to-1 ratio. Combine three cups of baking soda with 1/2 tsp of Prussian blue pigment powder from art stores to make your own powdered bluing. Alternatively, you can create a Prussian blue suspension from saturated solutions of iron (III) chloride and potassium ferrocyanide. Mix 3.7 grams of iron (III) chloride with five milliliters of distilled water in one beaker. Mix 1.39 grams of potassium ferrocyanide with 5 milliliters of water in a second beaker. Pour the potassium ferrocyanide solution into the beaker with the iron (III) chloride solution and stir with a glass rod.
Crystal Experiments Without Bluing
You can carry out fun crystal experiments without liquid bluing or Prussian blue suspension. Add a spoonful of Epsom salts to a cup of warm distilled water and stir until dissolved. Continue until the solution is saturated (i.e. no more salts will dissolve). Let all the undissolved salt settle on the bottom of the container then slowly pour off the solution into a bowl, stopping before you get to the undissolved salt. Put the bowl in the refrigerator for three hours and you will see crystals beginning to form. You can also do crystal experiments with table salt, alum, washing soda and borax.
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Claire is a writer and editor with 18 years' experience. She writes about science and health for a range of digital publications, including Reader's Digest, HealthCentral, Vice and Zocdoc.