Study Guide will be provided before the final exam.           

Alum crystals are among the quickest, easiest, and most reliable crystals you can grow. Did you know you can make them glow in the dark by adding a common household ingredient to the crystal growing solution?

Glow in the Dark Alum Crystal Materials

• fluorescent highlighter pen (I used yellow, but you can use another color for different colored glowing crystals. Check to make certain the highlighter will glow under an ultraviolet or black light. Pretty much all yellow highlighters glow, as do most other colors. Many blue pens will not glow.)
• alum (sold as a pickling spice)
• water

 Grow Glowing Alum Crystals

1. Carefully cut open the highlighter and remove the strip that contains the ink. You may want to wear gloves, since highlighter can stain your fingers.

2. Pour 1/2 cup of hot tap water into a clean container.

3. Squeeze the highlighter strip into the water to color it with the fluorescent ink. Discard the ink strip when you are finished.

4. Slowly stir in alum, a little at a time, until it stops dissolving.Loosely cover the jar with a coffee filter or paper towel (to keep dust out) and allow the jar to sit undisturbed overnight.

5. The next day, you should see small alum crystals at the bottom of the container. If you don't see crystals, allow more time. You can let these crystals grow, though they will compete with each other for material.

6. Alternatively, you can use one of these crystals to grow a large single crystal.

   Growing a Large Single Crystal

1. If crystals are present, pour the alum solution into a clean jar. Collect the small crystals, which are called seed crystals. 
2. Tie nylon line around the largest, best-shaped crystal. Tie the other end to a flat object (e.g., popsicle stick, ruler, pencil, butter knife). You will hang the seed crystal by this flat object into the jar far enough so that it will be covered in liquid, but won't touch the bottom or sides of the jar. It may take a few tries to get the length just right.) 
3. When you have the right string length, hang the seed crystal in the jar with the alum solution. Cover it with the coffee filter and grow a crystal. 
4. Grow your crystal until you are satisfied with it. If you see crystals starting to grow on the sides or bottom of your jar, carefully remove your crystal, pour the liquid into the clean jar, and put the crystal in the new jar.

Making the Crystal Glow

When you are satisfied with your crystal, remove it from the crystal growing solution and allow it to dry. Just shine a black light (ultraviolet light) on the crystal to make it glow. Depending on the ink you used, the crystal may glow under fluorescent light or sunlight.

You can display your crystal or store it. You can wipe dust from a display crystal using a cloth, but avoid dampening it with water or else you will dissolve part of your crystal. Crystals kept in storage may be wrapped in paper for added protection from dust and changed in temperature and humidity.

True Glow in the Dark Crystals

If you want the crystals to really glow in the dark (no black light), then you stir phosphorescent pigment into a solution of alum and water. Usually, the glow will remain on the exterior of the crystal rather than get incorporated into the crystal matrix.

Alum crystals are clear, so another way to make the crystals glow is to mix phosphorescent pigment with clear nail polish and simply paint regular alum crystals. This also protects the crystals from damage by water or humidity, preserving them.

How To Grow a Borax Crystal Snowflake

Borax Crystal Snowflake Materials

String

wide mouth jar (pint)

white pipe cleaners

borax (see tips)

pencil

boiling water

blue food coloring (opt.)

scissors

Time Required: Overnight

Let's Make Borax Crystal Snowflakes!

1. The first step of making borax crystal snowflakes is to make the snowflake shape. Cut a pipe cleaner into three equal sections.
2. Twist the sections together at their centers to form a six-sided snowflake shape. Don't worry if an end isn't even, just trim to get the desired shape. The snowflake should fit inside the jar.
3. Tie the string to the end of one of the snowflake arms. Tie the other end of the string to the pencil. You want the length to be such that the pencil hangs the snowflake into the jar.
4. Fill the widemouth pint jar with boiling water.

1. Add borax one tablespoon at a time to the boiling water, stirring to dissolve after each addition. The amount used is 3 tablespoons borax per cup of water. It is okay if some undissolved borax settles to the bottom of the jar.
2. If desired, you may tint the mixture with food color.
3. Hang the pipe cleaner snowflake into the jar so that the pencil rests on top of the jar and the snowflake is completely covered with liquid and hangs freely (not touching the bottom of the jar).
4. Allow the jar to sit in an undisturbed location overnight.
5. Look at the pretty crystals!!! You can hang your snowflake as a decoration or in a window to catch the sunlight.

Tips for Success

1. Borax is available at grocery stores in the laundry soap section, such as 20 Mule Team Borax Laundry Booster. Do not use Boraxo soap.
2. Because boiling water is used and because borax isn't intended for eating, adult supervision is recommended for this project.
3. You can also try table salt (NaCl) but the crystals may not form as large or as quickly.