Kids should ask an adult for help handling the hot water. Distilled water gives the best results, but tap water should work fine. [1] X Trustworthy Source Science Buddies Expert-sourced database of science projects, explanations, and educational material Go to source As you heat the water, its molecules will speed up.
Table salt takes a few days to grow. “Iodized” salt won’t work as well, but will still form crystals. [2] X Research source Epsom salt grows into smaller, needle-like crystals, but grows more quickly than table salt. Buy it at a pharmacy. Alum grow quickly, sometimes making visible crystals within a few hours. Find it in the spice section of a grocery store.
You’ve just made a supersaturated solution. This means the solution (the liquid) contains more salt than water can usually hold! When you heated the solution (your water), the molecules sped up, creating space between them that allowed more of the solute (your salt) to be absorbed than usual.
Pour slowly and stop before the salt grains fall into the jar. If there are undissolved salt grains in the jar, the crystals might grow around those grains instead of your string. Since supersaturated solutions are very unstable, salt will come out of the solution when you disturb it. This means it will start to form crystals, which takes heat away from your solution. [3] X Research source
The tiny grooves and rough edges of the string provide a place for salt to latch on and grow. [4] X Research source A fishing line won’t work, since it’s too smooth.
Try not to have the string touch the side of the jar. This can make smaller, lumpier crystals grow against the side.
To grow a lumpy mass of crystals quickly, keep the jar in the sun and/or keep a fan blowing near it on the lowest setting. These crystals may stop growing at a fairly small size. If you want a single, large crystal instead of a clump of crystals, keep the jar in a cool, shaded place. [5] X Research source Keep it on a Styrofoam pad or similar material to absorb vibrations. [6] X Research source (There’s still a good chance you’ll end up with a clump, but there should be larger individual crystals within it. ) Epsom salt (and a few less common salts) will grow faster in the refrigerator instead of the sun.
When the water cools, it has way more salt than cold water can normally hold. This makes it very unstable, so the dissolved salt will leave the water and grab onto the string if it gets a tiny push. [7] X Research source As the water evaporates, the salt stays behind, making it even more unstable and encouraging the crystal to grow. This is because the crystal is in a lower energy state, which makes it more stable than the salt was in the solution.
Use a flat, shallow, wide container instead of a jar. This makes it easy to get a single crystal that hasn’t merged with any others. [8] X Research source Epsom salts do not work well for this method. Try alum or table salt instead, or see variations below for more ideas.
Choose a lone crystal, not in contact with any others. Choose a crystal with flat, even surfaces and straight edges. Choose a large crystal (at least the size of a pea). [9] X Research source Ideally, find several crystals and set each one up in a separate jar as described below. Crystals often dissolve or fail to grow, so having backups is a good idea.
Do not use string or rough wire. You need a smooth surface so the crystals can’t grow on the string instead of the crystal.
There are several faster ways to solve this problem, but they are more difficult and may require some knowledge of chemistry. [11] X Research source
Place the jar in a cool, dark location, such as in a low cupboard. Keep it on a Styrofoam pad or other material that absorbs vibration. Keep a coffee filter, paper, or thin cloth over the jar to block dust. Do not use an airtight seal.
About every two weeks, pour the solution through a coffee filter to remove impurities. [12] X Research source This is a difficult process. Even experienced crystal growers sometimes have a crystal dissolve or become lumpy. If you have a perfect seed crystal, you might want to test a worse seed crystal first to make sure the solution works out.
Borax for white or dyed crystals Copper sulfate for blue crystals[14] X Research source Chrome alum for purple crystals[15] X Research source Copper acetate monohydrate for dark, blue-green crystals[16] X Research source Warning: These chemicals may cause harm when inhaled, ingested, or handled with bare hands. Read the safety information on the label and do not allow children to handle them unsupervised.
Pour enough to saturate the sponges without submerging them. To make different colors of crystals, add a drop of food coloring to each sponge.
