Calcium chloride crystals are easy to grow. The clear crystals are thin, six-sided shards that sparkle brightly.
All you need is calcium chloride and water:
- Calcium chloride (CaCl2)
- Water (H2O)
Calcium chloride is commonly used as road salt to remove ice, in moisture control products such as DampRid, and in pure form as a common chemical. In some products, it is mixed with other salts, so it’s a good idea to check the ingredient list. It’s typically seen as crushed crystals or as a white powder.
Grow Calcium Chloride Crystals
Growing calcium chloride crystals is basically the same as growing table salt crystals. In general, the solubility of any salt greatly depends on temperature. So, it’s important to dissolve the salt in boiling water, not just hot tap water.
- Heat water to a full boil.
- Stir in calcium chloride until no more dissolves. To make certain the solution is saturated, it’s fine to add enough calcium chloride that there is a bit of undissolved material at the bottom of the container.
- Let the solution cool enough that it’s safe to handle. Filter the liquid by passing it through a coffee filter or paper towel. This should keep any floating contaminants and undissolved salt out of the growing container.
- Place the container in a location where it won’t be disturbed. If you like, you can set a coffee filter or paper towel over the container to keep out dust. The amount of time needed for the crystals to grow depends on the rate of cooling and evaporation and whether or not you started with a saturated solution. Slower cooling and evaporation tends to produce larger crystals, but may take a few days. Quick cooling (by refrigerating the liquid) produces many thin needles within an hour or two.
Tips for Success
Usually you can remove crystals from their growing solution to examine and keep them. While it’s fine to take calcium chloride out of solution, be aware it is hygroscopic. This means the crystals will absorb water from the air and degrade.
While calcium chloride crystals are naturally colorless, you can experiment with colored crystals. Adding food coloring or dye to the solution probably won’t color the crystals. However, if you add dye to the solution and pour it into one half of an egg shell (with the inner membrane removed), the calcium carbonate of the shell will absorb the color. You’ll end up with a geode effect.
The “lazy” way to grow calcium chloride crystals is to hang a container of DampRid in your car. The temperature and humidity fluctuations will eventually produce crystals spontaneously!
- This project involves boiling water, so adult supervision is required.
- Calcium chloride is a powerful desiccant. Contact with the salt can irritate skin by removing moisture. Ingesting dry calcium chloride can cause burns in the mouth and esophagus. When the solution is dissolved in water, it’s not toxic, but drinking it can cause hypercalcemia. Basically, don’t handle the salt or the crystals and don’t drink the liquid. If skin contact does occur, rinse the affected area with water immediately.
Calcium Chloride Fun Facts
- Calcium chloride is one of the ingredients in Magic Rocks. Solid calcium chloride in water glass (sodium silicate solution) grows a type of chemical garden. NASA scientists explored the growth of these crystals on the International Space Station.
- Calcium chloride is a common food additive. It is used as road salt because it is safer for plants than sodium chloride and works at a lower temperature. It’s added to swimming pools to increase water hardness, to aquariums to increase calcium concentration, and in the manufacture of sports drinks, cheese, pickles, sliced apples, beer, and even bottled water.
- In medicine, calcium chloride is used to treat hydrofluoric acid burns, counteract hyperkalemia, and treat cardiac arrest.
- In veterinary medicine, a solution of calcium chloride can be used to sterilize male farm animals.