Q:

air trapped in sink drain?

A modest sized object had fallen into my bathroom sink causing (I assume) the sink to drain slowly.  That is, at first (after dropping the item) the sink seemed to drain fine but eventually it slowed to a bare minimum.  
The sink is a pedestal sink and the drain pipes are pvc with threaded and compression joints, so I took out all the pipes from basin to floor, clean everything (obstruction and all) and put it back together.  Everything was hand-tightened only: the only tool used was a toothbrush to scrub the parts clean.  
Now the water drains better but only slightly.  If there is still an obstruction, it would have to be in the floor, but we had no apparent problem before the one item I was able to extract.  On the other hand, now, as the water slowly drains, I can hear a trickle in the drain pipes.  As far as I can recall, this was not the case before I took it all apart.  So I'm guessing that there is air bubble somewhere.  Does that sound reasonable?  And if so, what can I do to deal with it.
Note that this is not a new works project; I simply disassembled, clean and reassembled everything.  I didn't add parts or have any parts left over.  At worst, I might have changed the order of parts or changed the spans between adjustable, compression joints.  But all the fittings and seals were put in place.

A:

There is probably soap and hair plugging the drain lower down. a small hand auger might be the best bet to clean it out. Chemical drain cleaners partially open the drain then they plug up again much quicker and you end up spending more on chemicals than the cost of the auger.  

