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UV emmission bands from BLB Fluorescent bulb?

Discussion in 'Lighting' started by JohnR66, May 14, 2005.

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  1. JohnR66

    JohnR66 Guest

    The subject line is my main question. Also What wavelength(s) are
    responsible for making some white objects glow bluish.

    The link below is an image illuminated by a 15w black light (note the
    reflection in the glass). Pieces of plastic and glass are placed over a
    white towel. The piece on the left is plain glass (blocks very little. The
    center is .093" thick standard acrylic. The piece on the right is glass with
    a thin coating of ?? that blocks a very high percentage of the UV. This
    glass is used in the picture framing industry to help control the fading of
    artworks. The dark strip along the bottom is .118 acrylic that blocks more
    than the thinner acrylic.
    http://home.att.net/~jriegle/uvtest.jpg
    I know standard acrylic blocks nearly all UV at 350nm, so I'd say the
    wavelength(s) responsible for causing the glow is equal to and/or longer
    than 350nm, correct?

    Thanks, John
     
  2. Ioannis

    Ioannis Guest

    There are two types of UV emission on BL(B) bulbs: Actinic and pure black
    light.

    "Actinic" refers to taking some of the lower wavelengths, like the
    254/313/356 clusters and converting them using a fluorescent powder to a
    continuum, with a peak either at ~370-375 or ~380-390, depending on type.

    This conversion is independent of the application of an additional "wood's
    glass" dark filter that black light lamps use.

    To get "pure" black light, wood's glass is used, as a plain filter on either
    a low or high pressure mercury discharge. When coming from a high pressure
    discharge, there is no actinic fluorescent coating. When coming from a low
    pressure mercury discharge, there is actinic fluorescent coating.

    When no fluorescent coating is used, this usually allows everything from 356
    on to 450nm through, unaltered, and the radiation there is linear with no
    continuum, containing all the UV lines of mercury from 356 and up to 450nm.

    For actinic radiation, a fluorescent powder is applied to a low pressure
    mercury discharge, which converts the 313 and 356 clusters (as well as the
    254nm if memory serves right) to a continuum which peaks at 370 and 390,
    depending on application.

    The BL(B) you have seems to me to be the type that contains both actinic
    fluorescent powder AND is filtered by wood's glass. (I can't tell from your
    jpg, cause both the filtered and the unfiltered actinics have very strong
    imprints on cameras and both the filtered *and* the unfiltered are termed
    "blacklight").

    It is true that acrylic blocks the 356 line, but it doesn't block the
    actinic continuum which peaks at 370/390, so your fluorescence might come
    from this area.

    To summarize:

    TLAK (BL): Actinic fluorescent with peaks at 370/390nm
    BLB: Black light fluorescent: Actinic + Wood's glass, peaks at 370/390 and
    filters out visible
    Black Light Mercury: Wood's glass only, contains all the UV mercury lines
    (and some visible ones), but no continuous actinic radiation.

    See:
    http://users.forthnet.gr/ath/jgal/spectroscope/Hg.html
     
  3. My experience:

    BLB has peak around 360 nm and dark violet-blue glass.

    BL has peak around 360 nm and untinted glass.

    Actinics have something different, such as wider bandwidth or longer
    peak wavelength. One example is the 03 actinic, which has peak around
    410 nm or maybe a few nm longer.
    I thought the longwave mercury line cluster was 365-366 nm and it is not
    utilized well (often not at all) by most fluorescent lamp phosphors. One
    blue-glowing phosphor used in at least some triphosphors and Philips
    "Special Blue" does have significant utilization of 365-366 nm.

    Phosphor utilization of 365-366 and 313 only matters a little, since low
    pressure mercury does not produce a whole lot of 365-366 or 313 but mainly
    254 with 185 in a somewhat distant second place.
    Acrylics vary. But in my experience the usual stuff mostly blocks 360
    and 365-366. The phosphor peak in BL and BLB is at a wavelength slightly
    shorter than that of the 365-366 nm mercury line cluster, which is far
    weaker than the phosphor output. The phosphor output is strong at least
    from the low 350's to about 370, maybe a little wider. I have seen
    somewhat wider in at least some Sylvania and Moolim lamps.
    If it really peaks that long, then it's different from the BL lamps that
    I see in the USA, which peak around 360 nm.
    USA BLB lamps peak around 360. But even here BLB is made with Wood's
    glass and BL is made with untinted glass.
    In my experience in the USA fluorescent lamps referred to as "actinic"
    have untinted glass and a phosphor that differs from that of BL by peaking
    at a longer wavelength such as 410 or low 410's nm or by having a wider
    bandwidth that extends significantly into the visible violet.

    ------------------------------------------------------------

    Another one: The 350BL. This is an untinted blacklight fluorescent
    lamp with a peak wavelength of 350 nm. This is supposedly more attractive
    to insects than other blacklights with a peak wavelength of 360 nm, so
    350BL is used in bugzappers.
    It appears to me that the advantage of 350BL is its wider bandwidth. I
    have made a homebrew bugzapper and tried a few different fluorescent lamps
    in it, and my best results were with plain blue ("B"). As a result, I
    suspect insects find more attractive lamps that not only have peak
    wavelength in the blue-UV range but also wider bandwidth - possibly
    with spectrum not too different from that of clear blue sky. Also I found
    an advantage of running the lamp from DC and I suspect that insects can
    see 120 Hz flicker.
    One more thing about bugzappers with UV or blue lights: These do not do
    a good job of attracting houseflies, blue or green bottleflies or biting
    mosquitoes. Mosquitoes on the prowl for blood are focusing on what their
    targets emit - CO2, sweat odors, heat, any or any combination or all of
    these but not attracted much to light or UV that their prey does not emit.
    I had experience of bugzappers attracting mainly insects other than what
    I most wanted a bugzapper to kill, and this means things that attract
    enemies of mosquitoes, such as bats. In my year when I deployed a
    homebrew bugzapper with a DC-fed 20-watt "B" blue fluorescent lamp in
    springtime, I believe I made a dent in the local population (a goodly
    faction of a city block) in the bugzapper-attracted flying insect
    population, and this lasted a good 2, maybe 3 months. What I killed was
    mostly leafhoppers, and back then I thought this was good since
    leafhoppers suck juice out of plants. But now it appears to me that
    plants tolerate leafhoppers mostly fairly well (as opposed to other
    insects that feed on plants in ways or to extents that do significant
    noticeable damage). And in that year (1978) one thing that I noticed in
    the summer following my mid-late spring bugzapper deployment was that the
    bat population centered on a park almost 2 blocks away stayed closer to
    the park as opposed to doing some flying over my block. That summer, on
    my block mosquitoes were as bad as ever.

    One more thing about bugzappers: I have seen them attract and kill
    lacewings. Lacewings are good, since they eat aphids. I have seen aphids
    feed on plants to an extent that harms plants. In my experience,
    plant-feeding bugzapper-attracted insects are not much of a problem to
    anything, but do attract the enemies of the bugs that you want killed
    which are not as attracted to bugzappers. And in spring and summer, most
    species of aphids do not fly in most areas - in most areas, most aphid
    species have several generations per year with only the last significant
    generation of the year producing aphids that have wings. Since I never
    did bugzapper testing in autumn, I don't even know if bugzappers attract
    flying aphids, but in most of the time of year for flying insects in most
    areas with winters and flying insects, aphids do not fly.

    - Don Klipstein ()
     
  4. Ioannis

    Ioannis Guest

    Ï "Don Klipstein" <> Ýãñáøå óôï ìÞíõìá
    [snip]
    Don,

    The 350nm peaking actinic exists in Europe as well, although it is mostly
    used in copiers using NH4. I've used to own one of these.

    Please note that all my books are packed and stored, so memory may be
    failing me somewhat, but I do recall that the peaks that the Philips TLAK
    actinic uses for bugzappers in Europe were 370/390.

    On the link I gave, one can see the continuum radiation in one of the photos
    extending all the way to the visible.

    You are also right in that the actinic powder probably utilizes the 254nm
    line more than the others (365/313). It is probably the reason actinic
    fluorescent powder is used only in fluorescent tubes and not in the high
    pressure mercury version, which produces comparatively less 254nm radiation.

    [snip for brevity]
     
  5. The idea, then, is to buy one of those mosquito traps that burns propane
    to emit CO2 and heat as a lure...

    ....and give it to your *neighbour*.

    Bugzappers are mostly good as fun toys for young summer camp attendees,
    not for materially reducing the population of nuisance insects.
     
  6. JohnR66

    JohnR66 Guest

    Great information guys!
    BTW, I googled and found that soda-lime glass blocks nearly all UV at 300nm.
    At what wavelength is it blocking 50%? 90%?
    Thanks, John
     
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