This question is a puzzler.  UV shields cut out ultraviolet light; infrared
light (from the opposite end of the spectrum) is responsible for heat
build-up.  But plastic holds heat in a system longer than, for instance,
glass.

So, plastic UV shields can be expected to allow greater heat build-up in a
fluorescent light fixture.  On the other hand, the shields are not sealed;
heat can be expected to escape readily from the ends of the shields.

You state that the shields were recently installed and that the facility
director has determined that the shielded tubes are burning out 60-70%
faster than those without shields.

My experience is that fluorescent bulbs burn for years, with or without shields.

Before making a decision one way or the other about the UV shields, I would
check the ballasts in the lamps in question and also check the stability of
power from the transformer supplying the site.  I have noted that low
voltage has a very deleterious effect on the life span of fluorescent
lamps.

You don't say so, but your description suggests that the lamps in question
are inside exhibit cases.  This is not good.  If the ballasts are inside
the cases there can be a great deal of heat build-up just from the ballasts
and this can cause damage to the fluorescent bulbs (and the artifacts....)
I once worked at a site where it was so hot that fluorescent lamps turned
off about 3:00 pm each day.  And so did the crew.

There is an additional danger if fluorescent light ballasts are inside the
cases.  Ballasts are transformers; wire wrapped around metal plates in tar
or some other nastier non-conductive material.  If a ballast becomes hot
enough it will ignite creating a dense, black, particulate laden, foul
smelling, hazardous smoke; dangerous to people in the area.  It doesn't do
the artifacts in the case any good either.

Jack

>Date:    Tue, 2 Sep 1997 19:27:49 EDT
>From:    "Olivia S. Anastasiadis" <[log in to unmask]>
>Subject: Re: UV tubes
>
>We recently installed Filter-RayUV Shields from Light Impressions.  Our
>facility director has noticed that the fluorescent tubes we sleeved, with
>these u-v shielding acrylic tubes, are burning out 60% to 70% sooner than
>they wouldíve without the shields.  He suspects that the heat buildup is
>causing our fluorescent tubes to burn out sooner.  Further, the display
>case where we are using this product doesnít have electronic ballasts for
>the fluorescent we use.  Is this a contributing factor?

(snip)

>Olivia S. Anastasiadis, Curator
>Richard Nixon Library & Birthplace
>18001 Yorba Linda Boulevard
>Yorba Linda, CA  92886
>(714) 993-5075; fax (714) 528-0544; e-mail:  [log in to unmask]


Jack C. Thompson
Thompson Conservation Lab
7549 N. Fenwick
Portland, OR  97217

voice/fax: 503/735-3942

www.teleport.com/~tcl/