UV and Glass, Whats the truth?

Discussion in 'General Discussions and Advice' started by lIghty, 24 Nov 2009.

  1. lIghty

    lIghty

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    So, when installing a DE MH light bulb its always been said that you need to place a piece of 4-6mm glass below it to shield out the harmful UV light, I've even advise this to others, but is this true?

    The reason I ask it because I've just built a UV exposure box for making PCBs, it uses 2 small 6w UVC bulbs, peaking about 350nm if I'm correct. The light has to travel through 2 pieces of 4mm glass (8mm total) before hitting a UV sensitive material, and guess what, it reacts extremely well. So that would mean that the light has no problem going thought the glass!

    So does the glass actually do something or are we mistaken? Found this on WIKI, it seems only glass with "Cerium(IV) Oxide" can absorb UV.

    [/quote
    while cerium(IV) oxide can be used for glass that absorbs UV wavelengths (biologically damaging ionizing radiation).
     
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  3. Nemos Janitor

    Nemos Janitor

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  4. lIghty

    lIghty Thread Starter

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    Sorry, my mistake, it is UV-A.

    So it would help if I ran these lights on my tank? But Actinics are aslo in the same range?


    Thanks Nemos Janitor

    I Found this, thought it would help?:

    Light Spectrum

    The most obvious use of lights is to light the tank so that you can see your fish. Light spectrum runs from violet on the short end (320 nanometers) to red on the long end (700 nanometers). Remember your red, orange, yellow, green, blue, indigo, violet light spectrum? Below are two light bulb spectrums represented visually by peaks and valleys on a ROY G BIV scale.
    [​IMG]
    The sun has 3 wavelengths: UVA, UVB, and UVC. UVA is the visible wavelength of light and is responsible for the "physiological well being" of fish. The 420nm blue (UVA) range is particularly important to marine corals and invertebrates and also helps stimulate feeding and breeding behavior in fish.
    UVB is the non-visible wavelength of lighting. UVB is the spectrum which gives humans a suntan. This is a critical component for reptiles in that the 320nm range of violet (UVB) is needed for many animals to assimilate calcium into their systems.
    UVC is the wavelength used for Ultraviolet Sterilizers which kill harmful bacteria. This wavelength is very dangerous to all animals.
    Different spectrums are required for different species who dwell in different latitudes and at different water depths in their natural environments.
     
  5. viper357

    viper357 Admin MASA Contributor

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    I once tested a 150w DE 20 000K bulb to see what the colour was like, but I forgot to put back the piece of glass, I think it was 2 or 3 days later I wondered why all the corals were so limp, all polyps retracted, all the coralline algae had turned white, it really looked very sad on that side of the tank, then I realised I had forgotten to put the glass back.
     
  6. Pads

    Pads

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    Good question, Tagging along

    A little worrying as I'm planning a 70w MH Setup with 1 20k and 2 14k. I don't wanna damage anything in the tank. Might influence my placement of corals. How high were you globes from the section that got "bleached"?
     
  7. Bob the (reef)builder

    Bob the (reef)builder

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    A client once had the very thin shield pop on a 250w single ended light over his tank. He did not notice for a couple days. Killed lots of corals and a clam.
     
  8. viper357

    viper357 Admin MASA Contributor

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    They were about 20cm's from the water surface, but don't worry, as long as you have the glass in place you'll be fine.
     
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