How do you celebrate National Chemistry Week? Growing big, beautiful crystals, of course!

BUFFALO, N.Y. — When University at Buffalo chemist Jason Benedict started a national crystal-growing contest last fall, one thing he didn’t anticipate was how fast the contest itself would grow.

“I actually just had to order more materials because I had so many people sign up,” he said.

Now in its second year, Benedict’s U.S. Crystal Growing Competition is drawing dozens of entries from coast to coast. The annual event is open to children and teachers, and 60 teams from more than 20 states have signed up.

Crystal-growing officially begins on Oct. 19 to coincide with National Chemistry Week.

Benedict, an assistant professor of chemistry, predicts that it’s “going to be a lot of fun.”

“It helps foster competitive spirit and it also teaches students how to do science,” he said. “They’ll learn basic laboratory techniques, such as weighing out materials. They’ll learn to think creatively.

“I’m hoping it sparks a curiosity in them: What is a crystal? Crystals grow, but what does that mean? Crystals can be very different — they can be cloudy, they can be clear, they can be big, they can be small. What causes these differences?”

The contest has the cachet of being sponsored by the American Crystallographic Association — which is based in Buffalo — as well as the Western New York Section of the American Chemical Society, Bruker, Krackleler Scientific, the National Science Foundation, Ward’s Science and the UB Department of Chemistry.

What: U.S. Crystal Growing Competition

When: Crystal-growing begins on Oct. 19 and lasts five weeks, ending on Nov. 23.

Participants from Florida to Wisconsin to California will then carefully package their crystals and mail them to UB, where the entries will be judged anonymously by a panel of scientists in December.

Who: K-12 students and teachers will grow crystals made from aluminum potassium sulfate, a nontoxic chemical used in water purification and more.

Local entrants this year include a team from the Charter School for Applied Technologies led by science teacher Torrey Black, whose classroom won first place in the 9-12 category last year.

What makes a winner: Judges will be looking for qualities familiar to people who have shopped for a diamond ring: size, clarity and shape all matter. A good aluminum potassium sulfate crystal is colorless, transparent and octahedral (meaning it has eight primary sides).

How to grow a great crystal: Children and teachers will grow crystals by dissolving powdered aluminum potassium sulfate into water, then letting the water evaporate slowly. This causes the chemical compound to emerge from the solution and slowly form a crystal.

The trick to growing a big, beautiful crystal is fine-tuning the evaporation rate: Let the water disappear too slowly and the crystal will grow very slowly. Go too fast, and too much of the compound will crystallize, leading to imperfections called “occlusions,” or even to multiple crystals forming instead of one large crystal.

Fun fact: With “Chemistry Colors Our World” serving as the theme of this year’s National Chemistry Week, Benedict received a question from one team asking if they were allowed to dye their crystals.

His response: Sure, they could do it; but in general, adding dye lowers the quality of a crystal by putting it at risk for impurities.

For future years, he’s considering some kind of “cool crystal sub-contest” for dyed or other artistic crystal forms. “It’s definitely on my radar.”