UV or is it??

Discussion in 'Fly Tying' started by Jack Devlin, Aug 9, 2012.

  1. silvercreek

    silvercreek Active Member

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    Hi fellow listers. If you will allow me a comment, I would be grateful.

    Regarding taking UV flashlights to test materials in a fly shop, JWK is pretty much right on. There is UV fluorescence and reflectance. Jack is testing for fluorescence.

    My comment is that the UV flashlights that are used for UV acrylics such as Clear Cure Goo, are really near UV lights in the upper UV A spectrum. The are about 400 nanometers and 400 nanometers can be seen by the human eye. Indeed, we can see the light from these flashlights because they are just above the 390 nm limit of the human visible spectrum. As a practical matter, if we didn't see them we couldn't tell if the flashlights were on or off.

    http://en.wikipedia.org/wiki/Visible_spectrum

    Birds, insects and fish can see further into this near UV spectrum.

    Near Ultraviolet​
    NUV​
    400 – 300 nm​
    3.10 – 4.13 eV​
    visible to birds, insects and fishes​


    http://en.wikipedia.org/wiki/Ultraviolet#Subtypes

    What the UV flashlights cannot test for is fluorescent material that responds to a wavelength that is shorter and a higher energy than the near UV flashlight emits. So although the flashlight can confirm that a material fluoresces, it cannot confirm the opposite. A material that does not fluoresce with the light may fluoresce at a shorter wavelength. For example, it may absorb UV at 360 nm and emit in the 370 nm spectrum, both of which are invisible to us but may be visible to trout (see discussion below).

    Secondly, the UV flashlight cannot test for UV reflectance in the invisible UV range. It can only test for reflectance in the near UV range that it emits and that we can see.

    Regarding trout color vision. They have 4 cones to our 3. Our "blue" cone response peak is at 440 nm. Trout also have a 440 nm cone but they have an extra cone that peaks at 355 nm, well into the UV A spectrum. This is the cone that allows trout to see well into the invisible (to us) UV range. This cone regresses as the fish ages (thought to disappear at about 2 yo) but then thought by some researches to regain function during spawning.

    So smaller trout can see deep into the UV range but for most of the year, large trout cannot see anymore UV that we can. For spawning runs such as Salmon and Steelhead, UV regains its importance.
     
  2. jwg

    jwg Active Member

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    I thought the flashlights for curing UV resins are peak at 365 nm.

    I am sure that some UV adhesives have their peak sensitivity at 365
    (see Norland Optical Adhesives)

    And I am sure that some of the UV flashlights peak at 365 but with a broad peak that extends into the visible where we can see some light.
    Look at the UV LED spectrum on this page:
    http://store.advancedmart.com/336ulviuvled.html

    On the other hand there are also ones with 395 nm LEDs:
    http://www.phoseon.com/technology/led-uv-wavelength.htm

    Heres an LED system specially for UV adhesive curing that uses a 365 LED, spectrum shown:
    http://www.thorlabs.us/NewGroupPage9.cfm?objectgroup_id=4424

    Jay
     
  3. silvercreek

    silvercreek Active Member

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    Most of the multiple and single LED UV flashlights and even the laser pens peak at about the 390-400nm range. This is in the range of human vision. I have seen one vendor advertise a UV flashlight at 375nm but the vast majority of the IDENTICAL flashlights are advertised from 390 - 410nm. Most of these were advertised at 395nm so I think the 375 is a misprint.

    If the light were a true 365nm light it would need a spectrum spread into the 390+ range for us to see it. So the spread would have to be =/- 30nm or a 60nm range.
     
  4. Norm Frechette

    Norm Frechette Googlemeister

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    time to read and understand the new book

    [​IMG]
     
  5. jwg

    jwg Active Member

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    [/quote]
    If the light were a true 365nm light it would need a spectrum spread into the 390+ range for us to see it. So the spread would have to be =/- 30nm or a 60nm range.
    [/quote]

    The 365 LEDs do have a very wide spread, with intensity out into the human range of vision. Here is the emission spectrum for one of them, from one of my links in the provious post.
    Screen Shot 2012-08-15 at 7.50.45 PM.png

    I am not arguing that all UV flashlights have a 365 peak, but some do, and they have some visible light.

    I would be curious to get some links to some of the 390 UV flashlights. Most UV flashlights I see don't specify at all, which I find frustrating.

    Jay
     
  6. silvercreek

    silvercreek Active Member

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    JWJ,

    I PM'd you
     
  7. silvercreek

    silvercreek Active Member

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    Post removed
     
  8. silvercreek

    silvercreek Active Member

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    Post removed
     
  9. Jack Devlin

    Jack Devlin Active Member

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    I'm wondering what "power" the UV lights are that dentists use in curing fillings?
    jack
    PS Given all the wonderful information shared in this thread, I will have now to return to the fly shop where I said the material I purchased "had no UV as stated" and I will apologize for my ignorance (then).
    Jack
     
  10. toadthedry

    toadthedry Member

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    I spoke to a fly shop owner today who told me uv on many sirit river ( and i would assume other brands) products such as maribou and feathers actually stands for Ultra Visible. Not ultraviolet. Just a marketing ploy.
     
  11. Jack Devlin

    Jack Devlin Active Member

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    I really hate to think that is true. I don't know..............
     
  12. silvercreek

    silvercreek Active Member

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    According to Spirit River, your dealer is wrong.

    http://spiritriver.net/uv

    These are Spirit River's UV products. Perhaps you can refer your dealer to these URLs.

    http://spiritriver.net/uv2

    This is Spirit River's UV marabou. Bearsden says it is UV flourescent as their photo shows.

    [​IMG]

    http://www.bearsden.com/product10988.html
     
  13. Jack Devlin

    Jack Devlin Active Member

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    I didn't think this was correct. Spirit River is a decent company. Speaking for myself, I definitely need an education on things UV and florescent. I think some others do too. It is a relatively new thing to many of us.
    Jack
     
  14. toadthedry

    toadthedry Member

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    Thanks for the correction and link. I notice that that material is called UV2. I have spirit river stuff that has a UV sticker on it. Anyone know for sure if that stuff is real UV.
    Thanks
    Mike
     
  15. silvercreek

    silvercreek Active Member

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    UV2 may mean 2nd generation and UV 1st generation. Just a guess.