Traditional root beer was genuine beer. in the sense that its bubbles rose naturally as a byproduct of yeast fermentation The process of making this colonial drink began with the making of a syrup The brewer boiled molasses and water. approximately one a. half gallons of molasses to five gallons of water. and then let resulting syrup cool for three hours lnto the cooled syrup went a quarter-pound each of sarsaparilla root, bruised sassafras bark, and birch bark. Finally, the brewer added a cup of yeast and enough water to fill the fermentation vessel. The mixture was allowed to in this vessel.