ATM A few materials of choice

["Dan Chaffee" <dchaffee@gvi.net>]

Hi Richard,
Here is a small list of materials that I was able
to obtain info on at the conservation lab in the 
museum where I work. Geared towards the micro-environment
produced for the exhibition and preservation of ancient,
delicate art objects, it seems somewhat relevant to the 
containment and support of our optics. It does _not_ suggest 
that these materials will all ruin a telescope's internal 
components, but it might be worth considering when choices 
can be made. 

materials that off-gassed with deteriorating effects
(not clear as to whether it was  organic, 
or glass that was tested in addition to metals):

most unsealed plywood (formaldahyde & formic acid; formaldahyde
known to deposit crystals on glass)
unsealed partical board
Woods: oak, teak, larch, yellow & white pine, doug. fir, cypress,
redwood, red ceder and hickory
felt-_very_ bad when near silver, lots of sulfur
Scupt-Epox

materials that off-gassed little or neglegibly:

velvet
frame sealing tape
3-M #415 Double-Stick tape
silicone gasket
G.E. silicone caulk & adhesive (not RTV)
polyurethane foam & adhesives, paints & varnishes
acrylic & polyvinyl acetate adheasives
woods: spruce, poplar, balsa, birch, walnut, bass and
the least corrosive of all- politically incorrect honduras mahogany!

If the 'bad' woods are used, polyurathane vanish was the most
effective sealant.

Source: Conservation Guidelines, Design and Fabrication of
Exhibits. T. Raphael, 1986, 1991

D Chaffee
Kansas City, Mo.