In a 3-quart stainless steel saucier, combine blackberries, sugar, and salt. Using a metal spatula, crush the berries until the sugar dissolves . Using a kitchen scale, weigh the pot and fruit together, then make note of that number to track the reduction. Cook over medium heat until bubbling hot, then simmer, stirring constantly, until the mixture has reduced by 14 ounces . The time required will vary depending on the size, shape, and type of cooking vessel, as well as the size and output of the burner, but expect about 30 minutes, and adjust heat as needed to proceed at a similar rate. .
