Chemical Analyses of Silicon Aerogel Samples
  After five years of operating, two Aerogel counters: A1 and A2, taking data in Hall A at Jefferson Lab, suffered a loss of performance. In this note possible causes of degradation have been studied. In particular, various chemical and physical analyses have been carried out on several Aerogel tiles and on adhesive tape in order to reveal the presence of contaminants. 
I. van der Werf, F. Palmisano, R. De Leo, S. Marrone