A Depression flower garden is also called a coal garden or a crystal garden.
It’s a homemade set of colorful crystals. They’re a lot of fun for kids and grown-ups, and are a hands-on way of learning about crystal formations.
You begin by breaking up several charcoal briquettes and putting them into the bottom of a large glass dish. In a cup, mix three tablespoons of salt and three tablespoons of water.
Stir well. Add to the salt mixture three tablespoons of ammonia and three tablespoons of bluing (found in the laundry section of your grocery store). Stir well. Be very careful not to get your face too close or spill this on your clothes as you prepare it. If any gets on your skin, wash thoroughly.
When your mixture is ready, carefully pour it over the charcoal briquettes you’ve layered in the bowl. Sprinkle it with some food coloringyour choice of colorsor you can leave it alone and let the natural colors alone make the magic.
Cover the bowl tightly and let it sit for several days, after which you should see crystals forming. If you’d like for them to keep growing, add another round of the chemical mixture of salt, water, ammonia, and bluing, taking care not to pour the liquid directly onto the crystals that have already formed.
There’s no real chemical reaction taking place in a crystal garden. What’s at work is evaporation. The ammonia speeds up the evaporation of the liquid at the bottom of the bowl.
The charcoal is a conduit for the salt and bluing particles (an iron powder called ferric hexacyanoferrate) to climb up when enough of the liquid has evaporated that they can no longer be supported in the mixture.
Adding more solution to your dish layers more particles on top of the old formations, making unique and intriguing shapes in a variety of colors.