Interestingly, as the Ph changes, so does water solubility and we did discover that super saturating the wash water with salt (sodium chloride, NaCl) causes some darker constituets to become neither salt water nor solvent soluble, and to stick to the insides of the separatory funnel.
They easily washed off with warm water later, so they were clearly water soluble constituets. and would have made the oil darker as well.
One added point, which ES touched on in another thread, the taste and smell profile are dramatically changed by the acetalation process. It no longer smells or tastes like hash oil, an interesting trait that all of the cannabis esters that we've extracted share.
In part, I believe that is directly related to the dark tarry warm water soluble mateial stuck to the inside of the separation funnel and the murky constituet that leave with the salt water washes.
While Stark profers that turning cannabis oil into its acetate increases its weight 25%, and that may well be true, we are actually losing weight overall, because of all the non cannabinoids that drop out.
More on that now that we have standardardized our process and I can get an accurate number.