During the first 5-10 days, the sap is a relatively clear liquid, but as buds begin to break and sap flow decreases the liquid becomes milky in color. This clouding accompanies large increases in the yeast content of the sap. Sap production varies from tree to tree, and from year to year. Some trees in a stand may produce no sap while others produce 25 gallons or more. Tests have indicated that trees on low-elevation south slopes produce best.
Some people have a special motive for watching for the first sap of spring.
They use it to make beer, wine or syrup. Birch sap can be used as it comes from the tree or it can be boiled to concentrate it. Probably the most sophisticated sap processing setup in the Fairbanks area is that of Mr. Carroll Phillips who has been collecting and processing sap since about 1968. Mr. Phillips currently taps about 400 trees to obtain 2,000-3,000 gallons of raw sap. He boils the sap using steam produced in a wood-fired boiler which was brought into Fairbanks in the early 1900's.