Oils aren't water soluble, but are oil soluble. Most conditioners have emollients/emulsifiers that allow for water and oil to exist harmoniously in a product, so when you are co-washing you are dissolving excess oils with the cationic and nonionic surfactants (those emulsifiers) that are in the conditioner. Some oils will penetrate the hair cuticle and condition, and the excess that the hair does not absorb is rinsed away.
This is under the same principle as the oil cleansing method. Oil dissolves oil.
4a/3c, fine strands, low porosity, medium density
Last relaxer: Jan 2010 - BC'd: 2/27/11