This is very interesting and weird at the same time! SWIM's FOAF has never done any sodium bicarbonate wash simply because conventional theory would predict that at that pH most spice would be salted and washed away. Indeed, he just dissolved some pure sodium bicarbonate in water and no matter the amount added he could not raise the pH above 8.1.

But again, "conventional theories" and "spice" do not mix together very well, do they?

Possibly the secret could be the fact that you do not wash for extended periods of time? Maybe freebased spice actually takes some time to be salted at this marginal pH? Or your baking soda could contain other things as well, like sodium tartrate?