"Basically, snowmaking is trying to take water and atomize it into small droplets and freeze each one into a snow crystal from the time it leaves the nozzle to when it hits the ground," said Charles N. Santry of Snow Economics.

"There are many ways to make it happen and create a crystal that's a snowflake. It's not a dendritic crystal like mother nature makes, but a light crystal with a density lower than an ice particle," Santry said.

"There needs to be an actual snow crystal that starts to form an actual white core that's really natural snow, but we're doing it in a short time frame. The crystal has to form in about 10 seconds - from when it leaves the nozzle to when it hits the ground - and that's the hard part," he said.

Snow Economics produces HKD air/water guns, energy-efficient snowmaking guns, which use less compressed air - the most expensive component of snowmaking - per gallon of water. Santry said HKD air/water guns use 50 to 100 cubic feet of air per minute (cfm) compared with 350 to 600 cfm older guns use to do the same job.

Snow guns fall into two basic types: air/water guns, and fan guns.

In air/water technology, an air hose and a water hose go to each gun, which mixes the two in a way that atomizes the water into tiny droplets and shoots them into the air so they can fall to ground while forming snow crystals.

Only a water hose goes to fan guns, which produce their own compressed air.

In both, nozzles are configured to produce water droplets of two sizes: smaller ones that freeze instantly into tiny particles of ice which mix with a spray of slightly larger droplets that form snow crystals around the particles in the 10 seconds they travel through the air.

Most ski areas deploy a mix of guns for use in different conditions.

"Recently most of the focus has been on high-temperature snowmaking, because there are less cold temperatures, and everyone's trying to get open earlier and earlier to extend the number of days of operation," Santry said.

One characteristic of compressed air is that it cools as it expands, in some cases dropping to 40 degrees below zero as it comes out of a nozzle. That helps a lot in converting water into snow in marginal conditions, Santry said.

Another key to efficient snowmaking, he said, is getting height into the process by raising the nozzles 15 to 20 feet off the ground, so the water droplets have more distance to travel and more time to form a snow crystal.

Snowmaking has evolved from a way to supplement a natural base of snow into 100 percent coverage at most ski areas in the Northeast.