Hi, I have made a foaming hand soap with Cocamidopropyl betaine and Glucotain sense (sunfloweryl Methylglucamide) as surfactants, some glycerin, citric acid, preservative and fragrance. The soap foam really well but it is difficult to rinse and it seems something is left on the hands. What could cause this? Any advice on how to fix this problem? Thank you in advance for your advice always so useful.