Patience is tough for kids, especially in today’s world of instant gratification. In this experiment, your kids will put a string in some colored salt water and watch and wait for crystals to grow. The crystals aren’t huge and spectacular, but your child can see them and a magnifying glass makes them easier to inspect.
All you’ll need is a clear container or containers, water, salt, food coloring and string. We used both kitchen twine and jute twine to see what would happen. The white kitchen twine worked best.
First, have your child put a few drops of food coloring in the container(s) that you are using. Then, have them cut a piece of string about six inches long. It doesn’t have to be exact. Help your child tie a knot or two at each end of the string.
Boil some water (a cup or two) and, when it is boiling, start adding salt to the water. Add a tablespoon at a time, stirring the mixture to dissolve the salt. Do this until no more salt will dissolve (you’ll see salt and it won’t go away no matter how much or how long you stir.) At this point, you can let the mixture cool a little so it’s not dangerously hot.
When cool, pour an eighth cup or so of the salt solution you’ve made into the container(s) containing food coloring. Let your child mix it and then have them place one end of the string into the colored salt solution. They may have to swish it around to get it to soak up the salt water since the string will want to float. Leave the other end of the string hanging over the edge of the container.
As the water evaporates, the salt that the string has absorbed will remain in the fibers on the string and form new, larger crystals on the string. Have your child check the string every day and, if they want to, record the results in their science notebooks. It may take several days before the water evaporates and the salt crystals form – it took ours five days to evaporate. Try not to let the end of the string that hangs over the edge of the jar or glass touch the counter, or the salt water will be wicked onto the countertop. As I said before, a magnifying glass is a fantastic way to look at the crystals that form on the string. Ask your child what shape the crystal are-cubes, spikes? What do they see? If they’re interested, have them draw the crystals and record their observations.
There are great books on crystals and gems at the library. Check them out!