The Phenomenon......

Have you ever noticed that if you place a large bottom glass vessel some where to dry, it almost never does dry inside. Classic examples (we have seen) are a rectangular VW head light (face down) or a lab glass boiling flask. A boiling flask is round on the bottom with a narrower neck.
See Florence Flask on the Wikipedia...

"Days and days can go by and even in the sun they will not dry. After a week or more they might - or not. "

Yet if we put the food processor together wet (I mean wet, right after hand washing it) it dries by the next day. The processor container is almost sealed on the top except for two tiny pencil lead sized holes. We can wash a wine glass and set it on the counter upside down wet and it will dry! We can stack wet bowls on each other (stacked not nested) and they dry.
Interesting...
Our head light still had moisture in it years later even in use...

Perhaps it is some ratio of the top to bottom.
The narrow neck of the vessel might be the problem.
Perhaps the way air currents move through them?
CLUES:
So far THE PHENOMENON only happens with glass (that I have observed) and not plastic.

Best Guess:

My best guess is that there is a vacuum (or pressure differential) created because there is a large rapid change of size. Evaporation, Convection and Condensation could happen on any cup, bowl or bottle drying but if the change of size is swift enough and great enough in ratio a change of pressure results and that change effects the drying. The lower pressure is in that larger part...

What is your best guess?

What effect will placing a simple straw or tube placed in the flask have on the drying process? Or a U shaped Straw?

So far the flask is not dry or even close to dry, where the dishes are dry or have dried twice or more as 48 hours have passed. The real goal is not to dry the flask but understand the PHENOMENA. Can you run a mental simulation that will give you real results?

How about tipping the flask opening to level with the side? Note that care was taken to tip the flask so that opening is the same as the top of the large part of the flask. This was done in an effort to allow gases/vapors to escape.

Here it is (shown below) the next night (72 hours) and the flask is still wet inside. We were a little surprised at the results of tipping the flask. The flask did not dry (no surprise) but the moisture rather than being at the highest points of the flask were somewhere else. Care to guess where?

The moisture seemed to be orientated towards the brightest part of the room. The flask was sitting on a counter like surface in a wooden bowl to prop it up. The bowl was near the north side of an indoor wall almost 20 feet from the north window. The moisture was orientated towards the window. No direct sunlight could have hit the flask and we did not run the heat all day. If the sun was out the flask would have been in the shade, yet the flask is even further in the shade that just that, it is two rooms away from that sun. Interesting...