Mix together the molasses, sugar and spices in a large mixing bowl. Dissolve baking soda in hot water, and stir into the molasses mixture. Add melted butter and raisins; mix well. Add sifted flour and salt a little at a time. Pour mixture into a large, damp, floured pudding bag and tie the bag tight. The pudding batter should not be sticky or wet; it should be an almost play dough-like consistency when you put it in the bag. Steam in a large pot of boiling water for 2-3 hours, or until the pudding seems firm inside the bag. (If the bag starts to float, weigh it down in the water with a plate on top of it.) Serve with Grampy Ennis’ Custard Sauce.