This foamer is highly effective and costs "pennies" to make. Since foamers are usually an interactive feature it is wise to keep the solution you use kid friendly. R.A.D. (Rick's Alternative Detergent) works. Also, 1 cup of water (or less) with 1 tablespoon of baby shampoo will work well and won't sting the eyes. Mike Ashe has demonstrated using 1 tablespoon of CAPB (an ingredient in RAD) that made, what seemed to be, an endless amount of foam just by spreading the CAPB onto the surface of the foamer. Mike reports that he has also had success using 3 cups of water, 2 tablespoons of CAPB and 1 tablespoon of scented baby shampoo.