Choosing the right combination of oils in your soap bar recipe is very important, they all provide different qualities to your bar of soap. You need some that provide hardness as you don’t want your soap bar to turn to mush as soon as it gets wet. Then depending upon the purpose of your soap you need to put in oils that provide cleansing power. Shampoo bars need to be quite powerful cleansers to remove oils from the hair, but facial soap needs to be very mild to protect the delicate skin of your face. You also want to add oils which will moisturise the skin, leaving it feeling soft and comfortable after cleansing.
The qualities of soaping oils depend upon the fatty acids they contain, each different oil has a completely different profile of fatty acids. There is a wonderful table on the SoapCalc website highlighting the different fatty acids and showing which qualities they will bring to your soap.
http://www.soapcalc.net/info/SoapQualities.asp
If you are having a problem with a recipe and you want to increase any of the properties listed in the table, then look at which fatty acids will provide these qualities in your soap bar.
For example if I wanted to increase the cleansing values of my bar I would need to add lauric or myristic acid.
SoapCalc also has another really useful page which then tells you which soaping oils contain the highest percentages of these fatty acids.
http://www.soapcalc.net/calc/OilList.asp
To find oils high in lauric acid, click the lauric acid button and it will sort the oils in order of % lauric acid content. Common oils like palm kernel oil and coconut oil come high on this list with 49 and 48% lauric acid. Therefore these are the oils I would look to add to my bar to increase cleansing.
I hope this explanation is useful, If you have any questions then feel free to drop me a comment and I will do my best to help.