Maple Syrup

The Rule of 86

By Richard DeVries

It is taking a long time this spring for the sap to start flowing. The ground is finally starting to thaw enough for the trees to pick up some moisture. On the south hill we have four main-lines that carry the sap from the tree to the tank. All four go in a different direction and are connected to smaller tubing that is connected to the trees on that section of the hill.

Yesterday, two of the main-lines had a steady trickle of sap, the two other main-lines were slowly dripping. The main-lines with the steady trickle were connected to the trees that are on the warmest spot on the hillside. Last week the snow melted first in those areas and the ground must have thawed there while other areas are still frozen.

The pressure gauge connected to a tree on the south hill was pointing at 18.5 PSI. I counted 88 drips per minute, slowly filling up the blue bag. The temperature didn’t drop below freezing and the Sugar Maples have been dripping all night. This morning the pressure gauge was still at 6 PSI and I counted 32 drips per minute.

RefractomoterYesterday I used a refractometer to check the sugar content of sap from multiple trees. The refractometer uses light to measure the density of the sap. The sugar content varied from 3.6 to 4.8 degrees brix. Brix is the unit used to measure the density of the sap and syrup. For practical purposes the brix value equals the percentage of sugar in the solution.

HydrometerI also tested the sap from the tank on the north hill with a hydrometer. This is the sap from all the trees combined that are connected to the vacuum tubing. The hydrometer has a certain weight and a scale to measure the density of the sap. It floats at a certain depth in the sap and the number at the same level as the sap will tell you the sugar content, In this case 3.4 degrees brix.

The sugar content in the first sap is usually higher than later in the season. At the end of the season it might only be 2 degrees brix. We average about 3 degrees brix during the entire season. We can apply the ‘Rule of 86’ to calculate how much syrup we can make from our collected sap.

The ‘Rule of 86’ is based on the weight of the sugar in one gallon of syrup and divide it by the weight of sugar in one gallon of one percent sap. The answer, 86.26, represents the number of gallons of one percent sap that needs to be evaporated to make one gallon of syrup at 66.5 degrees brix.

To use the ‘Rule of 86’ we divide 86 by the sugar percentage in our sap and we know how much sap we need to evaporate to make one gallon of syrup. Our sap in the tank was 3.5 percent, which means we would need about 25 gallons of sap to make one gallon of syrup.

We have collected about 300 gallons of sap – that should be enough for 12 gallons of syrup.

Saturday we will be testing our math skills by evaporating our sap. Stop by to see the process and count the gallons of syrup.


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