Hope this makes sense. I'm never good at explaining this stuff myself.
http://www.snowdriftfarm.com/askthechemist.htmlShea and mango are very high in unsaponifiable matter. If they are incorrectly heated, upon solidification they will form little fat granules or crystals that feel bumpy to the skin. These bumps will melt down when rubbed into the skin, but they can be annoying and unsatisfactory if added to a formulation that is supposed to be smooth.
To remove the graininess from your shea or mango butters simply heat the butter in a doubleboiler on the stovetop. Gas works best as it keeps a more steady temperature than electric. Heat the butter to 170-185F. This is NOT hot enough to damage the properties of the butters. Keep the temperature steady - between 170-185F - for 10-15 minutes. The steady heat will cause the fat crystals to be obliterated. Rapid cooling may help stop the crystals from reforming. If you find that crystals have reformed upon solidification, go back and repeat these steps, paying close attention to time and temps.