Adjust oven rack to center position and preheat oven to 300 degrees F. Pour sugar into a 9- by 13-inch glass or ceramic baking dish. Toast until the sugar turns ivory, about 1 hour. Stir thoroughly and continue roasting, pausing to stir every 30 minutes. The sugar will produce steam as a byproduct of toasting, so it must be stirred well to allow that moisture to escape. Stirring should also help move hot sugar from the edges toward the center, and cool sugar from the center toward the edges, for even toasting. Continue toasting and stirring every 30 minutes until the sugar has darkened to the desired degree, from a light beige to the color of traditional brown sugar, between 2 and 4 hours more.
