With various volunteers & interns, a comparison of the suction level of
vacuum cleaners (Rainbow & Nilfisks especially) across various settings
& machines has been a concern for a long time. Finally, we borrowed with
a manometer and anemometer and started to test various settings, hand
positions, etc. We found that the distance the tip of the nozzle was
held above the textile (or net) was more important than the suction
level. If you press the nozzle of the vacuum cleaner against the textile
you are running it at a suction level 4 times (400%) that of your
colleague, no matter what the setting. Keeping the end of the nozzle
about the width of a pencil above the textile was the most important
factor in uniformity. Go figure! See
http://www.si.edu/mci/english/research/technical_studies/gently_vacuumed
.html So when you finally get your suction under control, you might want
to borrow an anemometer from an industrial hygienist and measure your
actual suction power.

Mary W. Ballard
Senior Textiles Conservator,
Museum Conservation Institute, Smithsonian Institution
4210 Silver Hill Road, Suitland MD 20746 U.S.A.
tel: 301-238-1210 fax: 301-238-3709 
email [log in to unmask]