title_body: When making pour over coffee, why does it sometimes take a very, very long time to drip out of the filter?
upvoted_answer: The problem could very well be what Stephie was touching on; very fine coffee dust restricting the flow.
  I was having the same issue with my setup and was just going to live with it. That is, until I took off the hopper off of my grinder and saw really finely ground coffee stuck between the splines of the burrs. After brushing out the powder and a couple firm taps it was back to normal.
  Depending on the different beans along with their level of oil, grinds can build up on the the burrs and internals of the grinder rather quickly. After a bit of time the caked on and powdered grounds give way and fall down into the stuff you just grounded. When you try to brew a cup, the smaller lighter coffee grinds/dust flow down to the surface of the filter restricting the flow by blocking all of it's pores.