Grow Your Own Geodes

Last week I geared up for this year's Summer Library Program with a teen program.  We grew our own geodes!

I had found instructions on how to do this project months ago (thank you, Pinterest) as I was brainstorming summer program ideas.  Take a look at the instructions yourself on the Steve Spengler Science website.  This is a very easy science project to do at home since the tools needed are generally easy to acquire.  In fact, most of the supplies are probably already in your kitchen cabinets!  The trick with doing this experiment at the library is that it takes time for the crystals to grow, so we actually had to structure this project as a recurring program where the teens met briefly every day over the course of three days.  Because of this scheduling issue and because I needed to know exactly how much I needed to buy in terms of supplies, I was sure to require registration for this event.  In the end I had seven teens in attendance for this program.

It seems kind of silly to describe the step-by-step instructions when they have already been written out so well (see the link above), so I won't do that here.  But I will post the video - created by and included on the Steve Spengler website - which briefly outlines all of the steps.



Here are a few tips for doing this project with a group:

• The alum powder is the only ingredient that was challenging to find in the quantities that I needed for a group this size.  You should be able to find small amounts of alum at the grocery store in the spice section (alum is commonly used in pickling), which should be fine if you are doing this project at home with one or two children.  But if you are doing multiple geodes, it makes good sense to buy the alum in bulk.  I was unable to find alum in bulk at local stores, but you can buy it online through multiple sources, including Amazon.  We ended up making a trip to Nasco, an art, science, and education supply company which has an outlet store located in Fort Atkinson, WI (as well as an online catalog).  It is possible that alum may be easier to acquire in bulk locally during the late-summer canning/pickling season.
• Blowing out the egg, as described in Steps 1 and 2, was a little bit tricky, but it was definitely a lot of fun.  Just be sure to remind the kids/teens to only breathe OUT, not IN, while their mouth is on the egg!  I saved all of the egg innards (waste not, want not), took them home, and made two quiches.
• To get the water heated to the near-boiling point required in Step 9, we used a simple coffee pot without any coffee grounds.  We have a very large percolator here at the library that we use for meetings, and it was absolutely perfect for this job.
• We ended up using 24 oz. glass jars as the containers where we mixed the solution and, ultimately, grew our geodes.  These worked fine, but I kind of wish that we had been able to get containers with wider openings to make it easier to drop the eggshells in and, later, fish them out.  Glass measuring cups would have been perfect, but I was unable to borrow enough of these containers to go around.
• The programming room where we did this project has a sink in it.  While this isn't exactly a requirement for this project, there were a few moments when I was very glad to have the sink nearby.  The teens rinsed out their eggs to better clean them after cutting them open, and we dumped much of the liquid out of the jars before fishing out the geodes with a spoon since the openings were fairly narrow.  This also made doing the dishes very easy.

If you read the comments to this experiment, you'll see that some users complained that their geodes did not grow at all.  Fortunately, we didn't have any problems at all with our geodes!  I truthfully don't know why these users had trouble with their experiments.  We followed the instructions to the letter and everything worked fine.  

And since you've all been waiting patiently, here are some pictures:

The teens had a lot of fun with this project.  I think they really enjoyed the hands-on aspect of this program. Several of the teens also came up with some creative ways to alter the experiment that might yield some interesting results.  It was really neat to watch the gears turn in their brains as they came up with these ideas! Ideas for variations included:

• Create new colors by mixing the food coloring.
• Don't add any food coloring at all.
• Add the food coloring later in the crystal-growing process.  Would the intensity of the color change?  Would the older, deeper crystals be clear, while newer crystals had color?  
• Crow crystals on surfaces other than eggshells.  What would happen if you were to treat an object with a different shape with the glue/alum as described in Steps 5 and 6?  What if you simply did this treatment to the inside of a bowl?

Most of the teens vocalized an interest in trying the experiment again, either as another library program or on their own at home.  Success!