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Very Dark Black

  1. Jun 3, 2017 #1

    BillTre

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    I am considering making a small studio space for a video I want to make.
    It will have to hold a cubic meter of space in which I will have very small fluorescent objects 1 mm cube (see previous thread).

    Since I am not expecting to have the most flaming hot UV light driving the fluorescence I want a very dark background and I have been looking into very black paints or whatever else might be available.

    I am looking to cover something greater than 3 sq meters, maybe 4 or 5 (details not yet worked out).

    I have of course found Vanta (Vertically Alligned NanoTube Array) Black (the blackest surface covering available), but it is very expensive (330 pounds for a few sq. inches), kind of a defense department controlled substance, requires high temps for application and is not available to me. Vanta Black absorbs 99.965% of the light that hits it. Its used in optics and satellites predominately. Cool video and SEM.

    Alternatively, I have been looking into very black paints used in media productions (Rosco Supersaturated Velour Black, $21.15/quart) and have read a bit about black paint used in making optics.
    I am guessing that there are probably several people on this forum who make their own telescopes, I am wondering what experiences people have had with very black paints, such as Albrecht, deep-Black optical paint (10 Euros/375 ml).
    • Cost of covering a few square meters is an issue (the above prices seems reasonable to me), in addition to blackness.
    • Should also not reflect UV since I will be shining that around to excite the fluorescence.
     
  2. jcsd
  3. Jun 3, 2017 #2

    jedishrfu

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    What about black cloth?
     
  4. Jun 3, 2017 #3

    fresh_42

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    I would try black blackboard paint. The rough surface should minimize reflections and maybe even absorb light to some extend. But this is a guess I only make, because it could be a relatively cheap attempt.
     
  5. Jun 3, 2017 #4

    BillTre

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    I have tried a variety of black clothes and papers. Not very good in my experience.

    Those that I have seen are not all that black.
     
  6. Jun 3, 2017 #5

    fresh_42

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    Are you sure you aren't talking about usual black paint which is pretty smooth? The special surface of blackboard paint should help. Too bad that water isn't an option. It absorbs visible light well.
     
  7. Jun 3, 2017 #6

    jim hardy

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  8. Jun 3, 2017 #7
    damn that material should be able to be used in stealth fighter...btw is it absorbing spectrum beyond visible light?
     
  9. Jun 3, 2017 #8

    fresh_42

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    I don't think this is a healthy idea. I doubt that you can prevent it from affecting your lungs while "dusting it over". As far as I know this could be a sure way towards cancer. And it is so fine, that you will probably need very expensive filters. But in case money isn't important, then this would be the perfect solution: https://en.wikipedia.org/wiki/Vantablack
     
  10. Jun 3, 2017 #9

    BillTre

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    I think matte paint has something like talc powder added to it to give a rougher surface. Gloss is the smoothest kind of paint finish.
    Another approach I've read is painting on to a fine sandpaper, but rough enough to have peaks after the paint is on it.
    Although surfaces like black cloth are rough and might "trap" light in its interstices, the tops of the rough bits can reflect fairly well in at least some cases.

    The Vanta Black does a similar thing at a molecular level. Only the ends of the nano-tubes (which should be shaped like ends of toilet paper tubes) are exposed in this way for reflection. There is a spray-on form of Vanta Black where the nano-tubes are just in a jumbled up pile instead of all vertically aligned, so it would have more of a reflective surface in this manner.

    Toner: interesting idea. In printers, it gets melted onto paper (which probably makes it more reflective). I guess the proper carrier would leave it on top like sandpaper.

    I asked the producer about that. It is used in satellites because it is very resistant to being shaken off (because it has little mass and therefore little inertia). It is however easy to pull off with a tape pull test (put tape on and pull it off). The tape pull test is similar to the stresses it would feel from air friction and therefore it is not good for that. Embedding the Vanta Black in some protective carrier would create a reflective surface over negating its unique optical feature.

    Vanta Black absorbs well in UV and if I recall correctly, in the IR (good for absorbing heat).

    There can also be differences in reflectance depending on the angles of illumination and observation. If there are big differences in what I use, this could be controlled by the position of the light and camera.
    I have some cinefoil for example. It is a black anodized aluminum foil used in lighting (movies etc.). It is more reflective and angles close to it plane than perpendicular. Of course, its smooth too.

    The supersaturated velour black paint is reputed to have (answer to a question by someone not of the manufacturer) of 3.2% in the visible spectrum. it is a very thick paint that has to be diluted to be painted (it can be diluted 15x). It is reputed to fell like 800 grit sandpaper when dry, which was attributed to the high pigment density. Some pictures show low reflectance at low angles.
     
  11. Jun 4, 2017 #10

    Borek

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  12. Jun 4, 2017 #11

    dlgoff

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    Really?
    [​IMG]
     
  13. Jun 4, 2017 #12

    Dr Transport

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    high temperature flat black krylon for bbq grills works pretty well....
     
  14. Jun 4, 2017 #13

    Nidum

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    Use geometric effects . Basic idea of light being reflected away at an angle rather than straight back to source .

    Sloping backplane .

    One or more pyramids on backplane with point facing light source .

    Similar but with full width wedges .
     
  15. Jun 4, 2017 #14

    jim hardy

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    Just how vital is that last one or two % ?

    What made me think of copier toner is

    once i brought home a surplus office copier that'd been discarded at work. A really big one, size of a medium chest freezer.
    Purpose was to entertain the kids - give them some tools and something to take apart and they're happy for hours. They love to play with the wheels and gears, plus you get a lifetime supply of oddball machine screws and electrical connectors.

    Well it kept them busy three weekends. But on second weekend they got into its sizeable toner reservoir and had something akin to a water fight. They looked like coal miners and i'm sure the yard showed up on satellite photos.. But now looking back it's amusing . though next time i'd take it out first............

    Anyhow, that stuff is incredibly black.
     
  16. Jun 4, 2017 #15

    collinsmark

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    The motion picture industry uses duvetyne for such things. It's relatively cheap, easy to work with, and very very dark.

    With proper lighting and exposure duvetyne will pretty easily hide deep in the shadows.

    Film, CMOS or CCD sensors all have limited dynamic range -- more limited than the human eye. Even if you are able to make out minor details in a dark area with your eyes, the camera (with appropriate exposure) won't capture those details due to the narrower dynamic range; unwanted details will fall into the shadows.

    sddvbk.jpg
    [The photo above was taken with a higher exposure than would normally be used with this material as the background.]
     
    Last edited: Jun 4, 2017
  17. Jun 4, 2017 #16

    BillTre

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    Its probably not that vital, but I always like to consider the optimal extremes before I return to what is financial and practically realistic.
    For example, I tried to convince the Vanta Black guys to work with me on making a mini-studio of Vanta Black. It would be great for shooting miniature space ships (or whatever) in space. They declined, or actually didn't take me up on it.

    To some extent, problems can be fixed in post(-production: digital manipulation of the video, its all digital now).
    Also, the managing the lighting can reduce any illumination effects, as @Borek mentioned.
    I also got to mess around with UV filters which are cheap.

    In my searches for info on reflectance, I have found two kinds:
    • specular (which similar to a mirror reflecting light (angle in = angle out)) and
    • hemispheric which sends the light off in all kinds of directions.
    These numbers differ, and the difference differs for different materials (had fun writing that!).

    I'll look into this. I've seen some black backgrounds used in video production but I don't know that it was this stuff.

    Getting all this input is fun.
     
  18. Jun 5, 2017 #17

    OmCheeto

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    Speaking of fun, is it safe to assume you've checked out:

    BLACK 2.0 - The world’s mattest, flattest, black art material
    £11.99 ($15.43 USD) for 150 ml

    IT IS IMPORTANT TO NOTE: this is not the blackest black in the world. It is however a better black than the blackest black in the world as it is actually usable by artists.
    *Except Anish Kapoor

    *Note: By adding this product to your cart you confirm that you are not Anish Kapoor, you are in no way affiliated to Anish Kapoor, you are not purchasing this item on behalf of Anish Kapoor or an associate of Anish Kapoor. To the best of your knowledge, information and belief this material will not make it's way into the hands of Anish Kapoor.

    A video by the creator claims that 150 ml will cover "1½ - 2 meters worth of surface". (@ ≈2:00)
    He also paints a spoon, and recommends more than 1 coat. I would recommend a less expensive flat black primer.
    12 oz (355 ml) of Rust-Oleum is only $3.20.

    Other comments I've heard is that you should not touch the surface once dry, as it ruins the matte.
    It also picks up dust.
    I'm guessing these two facts are true of any matte surface.
     
  19. Jun 5, 2017 #18

    dlgoff

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  20. Jun 5, 2017 #19

    jim hardy

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    Can't quite tell which trace is felt. Bottom one ?
     
  21. Jun 5, 2017 #20

    BillTre

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    There's some pretty black materials in those links.

    It looks like its the bottom one since that trace is not on the original plot.

    I guess the source of the felt matters since I have some black felt that can be pretty reflective at certain angles.
    Looks like I should check out Edmund Scientific.
     
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