Hi-,I would add a small amount of the walnut shell powder to the soap, lets say 1 tsp per pound because its does become scratchy as the soap is used ..I use the fine grade powder..it makes a great exfoliating soap, just make sure to blend in as the soap cools a little, when it thickens a little so that it disperses evenly-unless you are using a suspension base , otherwise it will sink to the bottom of molds, but that looks nice too, you can have one side exfoliating and one side plain soap..