From the 17th century onward, dairy farmers who wanted to supplement their income from milk — or who just needed a source of sweetener that was better and cheaper than sugar or molasses — drilled small holes in the trees during the brief weather window between winter and spring. (Sap typically runs out of maple trees on days when the temperature is around 40F degrees following a night when the mercury dropped below freezing.) The farmers called the maple tree stands “sugar bushes” and hung buckets under the drilled holes. (The average maple tree, which can be tapped at 30 to 40 years of age, will produce 35 to 50 litres of sap per season.) Every day or two — depending on how fast the sap was running out of the trees — the farmers would empty out the buckets into larger containers or tanks and haul the watery substance to a “sugar house” usually built in the woods. Here’s where the magic happened.
It takes about 40 gallons of sap to make one gallon of maple syrup because sap is about 98% water. Sugar makers boiled off most of the water over a wood fire — what they were left with was brown sweet syrup. Some sugar makers heated the sap further, turning it into crystallized sugar. Over time, the industry evolved enough that companies from Quebec to Vermont produced ready-made “evaporators,” essentially giant frying pans with fire boxes built underneath. As quaint as this image is and as marketable — check out the old-time drawings on the sides of plastic maple syrup jugs — this is not the face of modern maple syrup making. These days, most serious sugar makers have foregone labor-intensive buckets, in favor of tubing systems. Sugar makers insert small plastic spouts into holes bored into maple trees and connect the spouts to huge webs of plastic tubing that route the precious sap into large tanks. Many of these sugar bushes have vacuum systems that suck the sap out of the trees to increase yield, along with oil-fueled furnaces and reverse osmosis filters that remove some water prior to boiling. The technology has changed dramatically, but in essence the process is virtually the same. Collect sap, reduce over heat. As the natural foods movement picked up steam, maple syrup has become, along with honey, an increasingly attractive alternative to processed cane sugar.
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Source:
Wikipedia Maple Syrup
History of Maple Syrup