Tag: alum’

Frozen: Crystallize Your Holidays

 - by KitchenPantryScientist




With the touch of her bare hands, “Frozen’s” Elsa coats the world with ice. It takes a little longer, but with your imagination, you can grow alum or Borax crystals on almost anything and make ordinary objects look extraordinary! (Directions for growing Borax crystals on pipe cleaners is near the bottom of this post. Borax crystals grow much faster than alum crystals and you can make snowflake ornaments overnight!)


We coated pipe-cleaner snowflakes, styrofoam snow people and even an evergreen branch with gorgeous ice-like alum crystals.

Here’s how to grow your own alum crystals:

Ingredients: alum (spice section of grocery store. 3 small containers for half recipe, 5 containers for 4 cup recipe. Alum is relatively expensive, so you might want to cut the recipe in half and crystallize smaller items! It’s cheaper to buy it in bulk at your local COOP.) glue, water, paintbrush,small items you’d like to coat with crystals.

1. Using a paintbrush, brush glue on the surface you want to “freeze”. One option is to twist 3 pieces of pipe cleaner together to make a snowflake. If you have beads, add them to your snowflake before crystallizing!

2. Before the glue dries, sprinkle the object with alum. These are your seeds for crystallization. Allow object to dry.


3.With adult supervision, dissolve about  1 1/4 cup alum in 4 cups in hot water (we use the microwave), reserving some alum to sprinkle on other objects you may want to make later. (One 1.9 oz. container of alum is around 1/4 cup, so you’ll need 5 of them.) Liquid will be cloudy and some crystals will sink to the bottom. This is your supersaturated alum solution.

4. Allow liquid to cool.

5. Suspend objects in alum solution until crystals are the size you’d like them to be. This may take an hour for small crystals or overnight for large one.  Remove the crystals from the jar and dry your crystallized object. We grew big crystals on our snowflakes and then scraped them off the beads, but left them on the pipe cleaners.


6. To crystallize more objects, reheat alum solution, stir up crystals to dissolve as many as possible, and cool before adding the next thing to be “frozen.”


To make Borax crystals, dissolve 10 Tbs. Borax in 3 cups of hot water and immerse pipe cleaners cut and twisted into snowflake shapes in the liquid. You don’t even need seed crystals to do this, since the Borax crystals will form on the pipe cleaner fibers on their own!

The Science Behind the Fun: Some crystals, like alum, will form from supersaturated solutions, like the one you used in this experiment. A supersaturated solution is one that is forced to hold more atoms in water (or another solute) than it normally would.  You can make these solutions using heat or pressure.  Crystals can form when a supersaturated solutions encounters a “seed” atom or molecule, or another impurity in the solution (like a pipe cleaner fiber) causing the other atoms to come out of the solution and attach to the seed. The more molecules attach, the larger the crystal will grow.  Here’s how to make rock candy with sugar crystals.

What else can you think of to crystallize?

Growing Alum Crystals in Eggshells

 - by KitchenPantryScientist

It only takes a spark to start a fire, and it only takes one atom to act as a seed for crystal formation. Under the right conditions, the atoms in alum will join together like puzzle pieces to form large crystals. I posted a few years ago about how to grow a large alum crystal, but this experiment is even more fun. It’s also easier for young kids, since it takes less small-motor coordination.

Alum is also called  potassium aluminum sulfate. It’s used in pickling and in found in baking powder. You can grow beautiful alum crystals at home with a few jars of alum, water and any object you don’t mind covering with glue. We made fake geodes by breaking eggs in half and washing them out, but we also encrusted a grape stem and a plastic shark.

To do this experiment, you’ll need glue, 3/4 cup alum from the spice section of the grocery store (4 or 5 small jars should do it,) water and whatever you want to coat with crystals. It takes three days to complete.

On day one, paint glue on the objects you want to grow crystals on. If you’re making “geodes”, apply a thin layer of glue to the inside of an eggshell that’s been cut in half, washed out and dried.  Then, sprinkle a little alum powder on the glue and let it dry overnight.  We heavily coated our object with alum, but might have grown larger crystals if we’d used less. Each alum particle acts as a seed for crystal growth. The closer together they are, the less room your crystals will have to grow.

On day two, dissolve 3/4 cup alum in 2 cups of water by boiling. This step requires adult supervision. Make sure all the alum dissolves (it may still look a little cloudy) and let the solution cool. This is your supersaturated alum solution.

After about 30 minutes, when the solution is cool enough to be safely handled, gently immerse your object in the alum solution.  For color, you can add a large squirt of food coloring. Let your project sit overnight to grow crystals.

On day three, gently remove your object from the alum solution and let it dry.  How does it look? Draw it or take a picture to put in your science notebook!

Crystals are geometric networks of atoms. Imagine a three dimensional chain-link fence, and you’ll get the picture. Certain crystals will only grow in certain shapes.  For example, diamonds are always cube-shaped when they form. Whether the atoms have joined to form a small diamond, or a large one, it will always be in the shape of a cube!

Some crystals, like alum, will form from supersaturated solutions, like the one you used in this experiment. A supersaturated solution is one that is forced to hold more atoms in water (or another solute) than it normally would.  You can make these solutions using heat or pressure.  Crystals can form when a supersaturated solutions encounters a “seed” atom or molecule, causing the other atoms to come out of the solution and attach to the seed.

What else could you try? Could you do the same experiment with salt, or sugar crystals? How do you think the color gets incorporated into the crystal? Do you think the food coloring disrupts the shape? Will larger crystals grow if you let your object sit in the solution longer?

You can read more about crystals and gems here.

Alum Crystal Mine

 - by KitchenPantryScientist

Imagine pieces of matter (too small to see) called atoms that will only fit together in a certain way, like a puzzle.  These atoms can attach to each other to form small three-dimensional shapes, or larger ones, but the shape will always be the same, depending on what kind of atoms make up the “puzzle pieces.”

This is what happens when crystals are formed.  Diamonds and salt, for example, are crystals shaped like cubes, while quartz crystals are formed in trigonal shapes, sort of like three-dimensional kites. You can have very small diamonds, or huge ones, like the Hope Diamond, which is as big as a silver dollar and blue from impurities in the stone, but they will all have the same basic shape.

We grew alum crystals in a jar last week and I am amazed at how beautiful they are.  I couldn’t get a very good picture, but they look like a string of real gems and were simple to grow.

To grow these spectacular crystals, you will need a small jar of alum, which can be found with the spices at the grocery store, water, a glass, a jar, a stick and some thread.

Fill the glass with about 3/4 cup of water and add a few teaspoons of alum powder.  Stir until the powder dissolves and repeat until no more alum will dissolve and you can still see some floating around in the glass.  Then, let the glass sit overnight or until some small alum crystals form in the bottom or on the sides of the cup.  It took two days for us to get some decent crystals, but we got several small ones that were fun to look at!

Fish a large crystal out of the glass with a spoon and tie a thread around it.  Tie the other end of the thread around the stick (we used a BBQ skewer) and wind it up so that you can rest the stick over the mouth of the jar and the crystal will hang down about half way.  Then, pour the remaining liquid from the cup into the jar.  There is still alum in the water, which will add more “puzzle pieces” to the crystal and make it grow bigger.

Now you can watch your crystal grow.  What shape is it?  Look at your crystals under a magnifying glass.  Take a picture of them, or draw them your science notebook!  Here is a link to a great Smithsonian website where you can learn more about gems and crystals.