Place 2 cups of light molasses in a heavy kettle and bring to a boil. Continue boiling (to 275 degrees to 290 degrees) for about 30 minutes, stirring constantly and being careful not to let it burn. When a drop of the hot syrup becomes brittle when dropped in a cup of ice water, add 1/2 teaspoon baking soda (it will boil up as you stir it so be careful not to burn yourself), mixing quickly.
Pour the hot syrup onto a buttered heatproof platter. Rub your hands generously with butter and pull the molasses to the desired light golden tan shade. Or, let it harden on the platter as is. Makes about 1 pound.