Solubility and Insolubility of Soap

Hello,
Im wondering how can a soap become insoluable after reacting with Ca or Mg. i dont know what would be reacting for:

Ca + R1-CO-O--Na+ ???

this gives something insoluable (a carbonate?)

which would become soluable after reacting with a aliminosilicate or some phophate (P3O9 3- or P3O10 5-)???

Thanks in advance :)

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True soap (Zest is not soap, it is a detergent as are most shampoos) is sodium stearate formed by mixing animal fat (stearic acid [C18H3602]) with lye (sodium hydroxide [NaOH]). The resulting esther, is fairly water soluble, but Ca and Mg stearates are far less soluble and form hard water soap scum. If there are other minerals dissolved in your water, there will be other insoluble stearates formed.

Thats why you don't use soap to wash your hair. You wouldn't want to be having to pluck all the precipitates out :P

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