Raising a butterfly

Our local kids museum has an annual adopt-a-caterpillar event. You get a very tiny caterpillar to take home in a small container. Over the course of a couple weeks you get to see it get bigger and bigger. Then, as jr. scientist A liked to recite, it would "build a cocoon, stay inside for two weeks, push its way out and be a beautiful butterfly!" (the last two words were always said loudly with arms up in the air). It was a really neat experience, although jr. scientist A was sad when we released our little friend into the wild.

Make-shift bubble blower

I promised jr. scientist A that we would make bubbles, but I couldn't find any of our bubble blowers. We decided to try to make some with objects we had around the house. One of the best bubble makers was an empty toilet paper roll. We dipped it in some bubble mix and then blew into the other end. If we blew slowly we got really big bubbles (although they often popped while still attached). It was a lot of fun, and when the toilet paper roll got soggy, we just let it sit for a couple hours and it was ready to be used again.

Meeting in the middle

Time for more fun with food coloring. We had previously used two colors to see whether salt water was slower to diffuse than fresh water. This time we repeated the experiment with two containers of differently colored fresh water. To our surprise, although the colors eventually seemed to meet in the middle, the red took days longer than the yellow color. It seems that whatever makes the different colors causes them to diffuse at different rates. We'll have to play around with that some more.

Crystal growing mediums

Since our previous attempts at growing stalactites have yet to yield anything remotely resembling a stalactite, we decided to take a step back and do some pilot experiments. There seems to be a few problems that potentially need to be addressed. 1) How do you get a nice slow drip for the salt water so that the crystals can grow over time? 2) What type of materials will the stalactites grow best on? 3) How do you refill your salt water solution without dissolving the already formed (water soluble) crystals (i.e., whatever makes the slow drip has to either never release the solution faster than a drip or be detachable)? I'm sure there's a few more we'll run into.

We've previously made some good progress on the first problem. We decided to attack the second problem by trying to grow crystals on different materials. We made our crystal solution, dissolving as much salt as possible in super heated water. This time we used table salt - nice and safe to handle and eat (good for a toddler hands-on experiment, that is, once the water has cooled). We poured the crystal solution over cardboard, paper, wood (a popsicle stick), and wool yarn. We set the materials in a window for a couple days and then checked on our results. The crystals grew everywhere (including on the plastic container the materials were in), but they just looked like big grains of salt on most of the materials. The one that stood out was the yarn (shown above, enlarged). There it seemed to form large crystal structures that looked like they'd be ideal for the beginnings of stalactites. I think we found our crystal growing medium!