First Frost

OK, it's way past first frost, but I've been so busy touring Alberta schools that I didn't have time to re-post a guest column that I made for the Sci-Why blog. At, a posse of kids' book writers - including Joan Galat and Claire Eamer - discuss science, words, and the eternal question - why? So if you want to find out about zombie ants, prehistoric scimitar cats, star-watching and more, take a look.

Here's my Sci-Why post about first frost:

Hi, I'm artist and author Carolyn Fisher. I write and illustrate picture books. Today, I'm pinch-hitting on the Sci-Why blog for Joan Marie Galat, who is gallivanting around Australia to look at stars in the southern hemisphere.

In my picture book The Snow Show, I wrote and illustrated a story about how snow is made.

When you're making a book, you do oodles of research. You brainstorm, you write, and then - if you're an illustrator like me - you draw zillions of sketches to plan out the pages. But because my editor gave me a 48 page limit on The Snow Show, there were lots of things that I left out.

Like how frost is made, for example. To today, in honor of dropping temperatures, I wanted to write about frost.

First, we have to talk about how snow grows. Here are some drawings that got rejected from The Snow Show.

Did you catch that? If the air temperature is below zero degrees Celsius (32 degrees Fahrenheit), water vapor molecules can change to ice without turning to liquid first. That's called DEPOSITION. Snow crystals form when floating water vapor molecules change by deposition directly into ice crystals.

There, I just summarized The Snow Show in three sentences. Can you believe it took me 48 pages to say that?

Frost crystals grow the same way as snow: water vapor molecules in the air freeze by deposition onto plants, glass, or snow surfaces. (Sometimes frost forms beneath snow surfaces: that's called depth hoar and it can cause avalanches if conditions are right. But that's a whole other blog post!)

For a snow study guide, download my free snow activity kit pdf here.