There’s something magical about growing crystals – whether you’re growing crystal names or growing crystal trees. No matter how many times we’ve waited for the stunning structures to appear, the surprise at what has grown never disappoints. This crystal tree demonstration is no exception.

The surprisingly simple experiment is the perfect addition to our top-selling Super Cool Science Kit!

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Getting Ready to Grow Crystals

The hardest part of growing crystals, besides waiting, is finding the key ingredient, Mrs. Stewart’s Bluing. (Other brands won’t work for this demo.)

Bluing is a laundry additive used to brighten whites and sometimes can be found in the laundry section of the grocery store.  I avoided the frustration of hunting it down and simply ordered it from Amazon here.

Once my bluing arrived, I gathered my materials:


  • Cardboard (the back of a paper pad works best)
  • Dish (large enough to hold your tree, with room for the crystal to grow)
  • Water
  • Table salt
  • Mrs. Stewart’s Bluing
  • Ammonia (optional, but speeds up evaporation)
  • Green food coloring (optional)
Before I called the kiddos over to mix up the magic crystal growing solution, I made the cardboard trees.  I used a ruler to mark out a triangle tree shape on the cardboard. I ended up making the tree 3 inches wide by 4 inches tall.

(The first time we tried this, I just eyeballed how big I wanted the tree to be.  It ended up being 6 inches wide at the base and 8 inches tall. I later learned that a tree this height is way too tall for growing crystals.)

After I cut out the triangles, I cut out the branches and used the first tree to trace the branches on the second tree.

When both trees were cut out, I cut a notch on the top of one and the bottom of the other so they would slide together.
We tried two different kinds of cardboard for this experiment to test the results (below). We used the back of a legal pad (the green tree) and corrugated cardboard (the white tree). The legal pad ended up working better for growing crystals. It took longer to wick the solution to the top but lasted weeks.

Making the Magic Crystal Solution

To make the crystal solution, my 5 year-old, A, simply mixed together all the ingredients in a dish:
  • 4 tablespoons warm water
  • 4 tablespoons table salt
  • 4 tablespoons Mrs. Stewart’s Bluing
  • 2 tablespoons ammonia
Before adding the cardboard tree to the dish of magic crystal liquid, A painted the it with green food coloring.
Then she placed the tree in the solution and waited for the magic to happen.  The first crystals showed up within a few hours.
The next morning, the kids ran to the tree to see many more crystals had grown.
Grow a crystal Christmas tree! What a fun Christmas science activity for kids.

Several days later, the trees were covered in delicate needle-like crystals.  My daughter thought they looked a lot like cauliflower.

My kiddos were so curious what the growing crystals felt like and since the white tree was getting pretty droopy, I let them go for it.

The structures are extremely delicate so, if you want to preserve the crystal tree for a few weeks, make sure you don’t bump it at all or the crystals can fall right off of the tree.
If you want your tree to grow more, just add more solution.
Awesome Christmas science for kids! Grow a crystal Christmas tree.

The Science Behind It

The solution we mixed up created a suspension, a mixture that has solid particles that are large enough for sedimentation (settling out).  Our solid particles settled out on the cardboard tree due to a couple of processes.

First, the liquid suspension is drawn up the cardboard tree through a process called capillary action.  Capillary action is the ability of a liquid to defy gravity and flow upwards.

In narrow areas, the combination of surface tension of water and the adhesive forces between the container and the liquid help to lift the liquid.  This effect can be seen when a plant like celery draws up colored water through its capillaries, when paint is drawn up between the bristles of a paint brush and when porous materials like cardboard draw up water.

The next process is evaporation, where liquid molecules escape from the solution as gas molecules.

Ammonia evaporates much quicker than water and we added it to the solution to speed up the evaporation process.  Once the solution travelled up the cardboard and evaporated, the next process could occur.

The final process, crystallization, occurred as the water and ammonia molecules leave the solution through evaporation.  The bluing and salt that remain can no longer be supported in the remaining solution and begin to crystalize.

Mrs. Stewart’s Bluing is a colloidal suspension of extremely minute particles of blue powder (Ferric Hexacyanoferrate).  These minute particles act as nuclei, or seeds, for crystallization to take place.  This is similar to the process that occurs in cloud formation.

The Super Cool Science Kit

For more science activities kids love, grab our Super Cool Science Kit packed with 30 jaw-dropping experiments and a ready to go science journal.

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