I have used: Crushed walnut shells Pumice Shredded loofah Coffee grounds Poppy seeds Green Zeolite clay My favorite for hand soap is the crushed walnut shell. However I would think the coffee grounds would have an added advantage of neutralizing smells. I like the idea of a recipe high in CO for sudsing and cleansing. Also, definitely use distilled water which is not the same as boiled tap water. Any tap water can contain minute quantities of minerals and metals that could react unfavorably with the soap product.