Back to the question…I find mica sprinkled across the top of soap will stain your counter/soap dish and I’ve stopped using red mica and charcoal in that way. I like biodegradable glitter for tops.
I used my younger sister and 5 of her friends as a test group. I learned some good stuff and I didn’t have to make less than 6 oz batches. But eventually those young ladies forgot my agenda and most of them didn’t bother responding unless nagged. THEN I found out my mother shared her samples...