Thanks.    The reason they put in filtering is because they would end up with 4-6oz of liquid completely separate from the bark, but would get double that if they fully filtered.  Feeling that they had bark in their hands and some time to spare, they would rather do extra work for a possible higher yield.  I'm sure they would be very interested in hearing the yields without filtering.     Another interesting thing of note (which was noted in the tek but possibly should be slightly expanded upon) is that if one is extracting during the winter months (whichever they are) in a cold enough place that it reaches freezing at night, small crystals form on the inside of the naphtha container.  These crystals provide a slight problem with freeze-precipitation if removed (they can be redissolved or the naphtha can be evaporated more to compensate), but are VERY pure...completely clear before oxidation.  Ones who have tried it found white spice to be a 'letdown' in comparison