Each January, when ponds and lakes freeze thick, Tim Graf passes on what he knows about the days before everyone had a refrigerator, when ice was harvested like a winter crop to keep food cold all summer long.

Using stories and tools passed on to him by his grandparents, who ran an ice business in Worthington, Minn., Graf teams up with naturalists at Three Rivers Park District to teach students and park visitors some living history by showing them how to harvest blocks of ice.

"My grandma lived until 99 1/2 and my dad is still alive, and I kept hearing all these stories about ice harvesting,'' said Graf, 60, a retired engineer who lives in Burnsville. "I have collected a couple truckloads of tools and toys and all kinds of information.''

The era of ice harvesting extended from the 1800s into the 1930s and early '40s, Graf said.

"Up until about World War II time, most people did not have electric refrigerators. So if you wanted to keep milk and cheese cold, they had an insulated box with a block of ice inside to keep everything chilled -- like a big cooler.''

Cutting the ice from the lakes was cold, rough work requiring long two-handed saws, giant tongs, ropes and horse-drawn ice plows to score the ice and wagons to haul it to storage.

Harvesters waited until the ice got 18 to 20 inches thick -- not so thick as to become unwieldy, but thick enough to form a 250-pound block of ice, Graf said. Right after Christmas was usually the time to begin.

Though they were working with sharp saws and piercing picks, the biggest danger for workers was falling into open water, Graf said. One day one of his grandparents' workmen fell in and started running for his home, desperate to change his clothes, but he was halted in his tracks by frozen pants, Graf said. Rescued by others, the man was carried home and put in a hot tub -- clothes and all.

Once the ice was cut, it was taken by horse-drawn wagons or sleighs to big barns known as icehouses for storage. During the summer it would be delivered, block by block, to homes and businesses, Graf said.

With ventilation and good drainage, an icehouse, painted white to reflect the sun, could keep ice cold until the following winter, Graf said. "My grandparents' icehouses held about 10,000 tons of ice. Once you get that mass of ice in one place, it's pretty hard to melt it just because of the sheer volume.''

Railroads were big customers for ice, using it to cool boxcars for the shipment of vegetables and beef, Graf said. "The railroads would build their own icehouses or buy it from people like my grandparents.''

Just about every town had its own ice company, Graf said. His family harvested ice on Lake Okabena near Worthington. Hiring carpenters, farmers and other tradesmen who needed part-time jobs in the winter, they cut about 40,000 tons of ice a winter -- about 1,000 tons per acre of lake.

People paid 25 cents for a 100-pound block delivered to their homes, Graf said.

"The ice man made a decent living. They owned all the equipment, the delivery trucks and the icehouses. Back in those days my grandpa was paying his best delivery guys 35 cents an hour.''

For kids used to seeing ice cubes tumble out of a refrigerator chute, the ice lessons are eye-opening, Graf said. Last week, he was explaining the process to students from Kenwood Elementary in Minneapolis and Highlands Elementary in Edina. He insists that the kids do the work, using the same saws and ropes and tongs as workers did decades ago to harvest ice -- just in smaller blocks.

Graf and the park district started the park ice demonstrations about 10 years ago, starting with a hole in the ice and one saw. "We have developed this into an annual event,'' he said.

Last week, during his demonstration at Richardson Nature Center at Hyland Park Nature Reserve in Bloomington, the pond ice was 15 inches thick. It took four kids at a time pulling together to bring a block out of the pond. Other groups sawed the blocks into smaller chunks for weighing or shaving or cubing.

When ice blocks were in use, a common household job for a child was to keep the pan under the icebox emptied to avoid flooding the kitchen, Graf told the students.

Ten-year-old Maddy McCue from Kenwood Elementary said she found the lesson interesting but wouldn't want to have to work so hard every time she wanted an ice cube.

"I would rather take it out of the fridge.''

Laurie Blake • 612-673-1711