How to Grow Borax Crystals

For explanations, mouse over (do not click) the following list of terms.
Borax
Concentrated Solution
Crystals
Evaporate
Evaporite
Saturated Solution
Solute
Solution
Solvent
Supersaturated Solution

Materials
pencil
craft stem- I used white
1-qt canning jar (hot liquids can safely be poured into canning jars)
2-quart cooking pot
2-cups borax (I used Twenty-Mule Team Borax purchased from the grocery store)
4-cups tap water (Use distilled water if your tap water is very hard.)
stirring spoon
canning funnel
oven mittens

Prepare Growing Surface for Crystals to Attach to

1. Twist one end of a craft stem around the center of a pencil.
2. Lay the pencil across the canning jar so that the stem hangs inside the jar. Cut the stem if necessary so that it hangs just above the bottom of the jar.
3. The borax crystals will attach to the surfaces on the craft stem.
4. Lay aside the pencil and attached craft stem. It will be used after adding the borax solution to the jar. 

Prepare a Supersaturated Borax Solution
Caution: I suggest that an adult prepare the hot borax solution and pour it into a jar. 

1. In a cooking pot, combine 2 cups of borax with 4 cups of water.
2. Heat on a stove with medium heat. Stir continuously until the mixture boils, then remove the pot from the stove.  All of the borax should dissolve. If not see step 4. (The borax solution is saturated at the boiling point of water)
3. Place a canning funnel in the jar as shown.
4. Slowly pour the hot borax solution through the funnel into the canning jar. Try to leave any undissolved crystals of borax in the pot.
5. Remove the funnel.
6. With oven mitts carefully move the jar to a place where it can be observed but disturbed. For best viewing have a light behind the jar, such as a desk lamp or a window.

Note: As the hot saturated borax solution slowly cools to room temperature, the solution has more borax dissolved in the water than normal. 

7. Place the pencil across the jar with the attached craft stem hanging inside the jar.

Tips:

•  Place the jar where it will not be disturbed–Do not shake or pick up the jar while the crystals are growing. This can cause the borax crystals to quickly precipitate forming forming a solid mass. You want tiny borax crystal to slowly form and grow. This happens if the solution is not disturbed as it cools.
• The jar should not be under an air conditioning vent or fan. Wind increases evaporation rate causing crystal formation to be more like one large mass instead of distinguishable geometric shapes. 

8. Observe the content of the jar immediately and periodically for the first three hours. When I grew borax crystals, once the first crystal specks were visible, the crystallization was not instantaneous, but from hour to hour I could see the difference in the size of the crystals. Generally, the crystals stop growing after 24 hours.

Results: The image gives you an idea of what borax crystals look like.

Summary

Borax crystals form naturally in nature from solution in much the same way as do the crystals in this experiment. In nature, pools of water with dissolved borax form. With no inflow of fresh water, as the water from the pool evaporates the concentration of the borax solution increases until the water cannot dissolve all the borax and borax crystals start falling out of solution.  Mineral crystals formed by this process are called evaporites. Evaporites are chemical sedimentary rocks.

Temperature affects the solubility of borax. Heating the water increases the amount of borax that will dissolve in it. When hot, more borax is dissolved in the water than would normally dissolve at room temperature. When hot, the solution is saturated with borax. As the hot solution cools to room temperature, the solution is said to be supersaturated because it has more dissolved borax than normally dissolved at room temperature.

A supersaturated solution is very unstable and shaking or stirring the solution can cause the excess dissolved borax to fall out of solution. In chemistry, solids that fall out of solutions are said to precipitate. At first, borax crystals that fall out of solution are microscopic in size, but the crystals have an attraction for each other and they stick together and grow until they are no longer buoyant in the solution. At this time they precipitate, fall to the bottom of the jar. With the craft stem in the solution, precipitating borax crystals first stick to the surfaces on the craft stem and attract other crystals that fall out of solution.

In any solution of any concentration, at the microscopic level, particles of the solute continue to dissolve and at the same rate particles of the solute fall out of solution. In other words, there is no visible change in a solution when the rate of dissolving equals the rate of crystallization. The solution is said to have reached a state of equilibrium.

Can Borax Crystals be Colored?–Yes.
The video has a different method for making the solution as well as the shape of the growing surface.

Something More

The borax crystals are so pretty. I’ve seen YouTube videos of how the borax crystals can be used to make necklaces. Use the following facts and questions to guide kids to do more research about borax as well as using the borax crystals in an extended experiment.

Facts: Yes, there is a lot of information in the following list of facts. Use what is applicable for your children. You can always repeat the experiment when kids are ready for the more complex information. Following the fact list is a Science Challenge.

1. You know that borax will dissolve in water. So, you couldn’t wear a borax necklace when it rains.
2. What about having borax crystals against your skin while you wear the borax necklace…Would there be any skin reaction since borax might dissolve in moisture on your skin?
3. How permanent are borax crystals? In other words, can you add borax crystals to your rock and mineral collection?
4. The chemical name for borax is sodium borate   Na₂B₄O₇·10H₂O Notice that there are ten water molecules attached to sodium borate (Na₂B₄O₇), thus borax is a decahydrate …deca-10;
5. Decahydrate borax crystals are translucent.
6. As  decahydrate borax crystals lose water from their chemical structure, there is a physical change in appearance from translucent to opaque. The hard translucent crystals begins to develop white powder on their surfaces.
7. When decahydrate borax crystals lose water, the slick surface of the transparent crystals  appear to be a chalky white. The mineral formed is called tincalconite and has this chemical formula, Na₂B₄O₇·5H₂O (sodium borate pentahydrate). Note that fewer water molecules are attached to the sodium borate.

 

Science Challenge—- 

Borax (sodium borate decahydrate) was used in the experiment to grow transparent sodium borate decahydrate crystals.
If  sodium borate pentahydrate, tincalconite, is substituted for borax, will the crystals that fall out of solution be the chalky tincalconite mineral or the transparent borax mineral?

Question:

When preparing the supersaturated borax solution, what affect would substituting the mineral tincalconite for the mineral borax have on the type of type of sodium borate crystals formed?

Hypothesis; Experiment;Results;Conclusion

More about crystals

How Ice Affects Food

1. What happens to food when it freezes?
2. Why does ice cream taste different if it melts and is refrozen?
3. Why is ice hard and a Popsicle is softer?

Find the answers to these questions about ice and much more in the book that I wrote abut Food and Nutrition. This book is available on Amazon as well as other book stores.