I recently inspected the filter screen on my Andair gascolator.  It looked clean even in sunlight with my reading glasses.  Then I took a look with a Jewelers Loop.  There were many fine fibers up to ¼ “ in length that could only be seen with the loop.  I picked them out with tweezers and it took a while.  Most of the accumulation was at the base of the screen at the lower cap.

When we went to the Advanced Pilot Course in Ada, Oklahoma a few weeks ago.  They made the point that more contamination is usually added than removed when a mechanic wipes or lays the “cleaned” injector screens on a “clean” shop rag.  Their advice, “don’t clean them”.

Steve Colwell  Legacy with a 550N