Then later we ask them to do by themselves at that point how do you explain to measure lye proposition.[/QUOTE
Do you mean lye concentration? I explain to them that every oil has a different SAP value so any changes to the recipe should be done using a lye calculator and direct them to soapcalc.net. The most that I cover in lye concentration is that there must be equal amounts lye and water to properly dissolve lye. The recipe I give is printed from soapcalc, so I tell them to use the same settings as the original recipe in any new recipes. The people that I teach are occasional hobbyists, or just trying it out, so I am not concerned that they need to understand the affects of lye concentration, that is something they can read up and learn on their own.