Turning a 2l soda-bottle into a "lightbulb"

Brazilian favela-dwellers without reliable electricity have an alternative means of supplying light to enclosed spaces that have no/insufficient windows (either because they are abutted on all sides by other buildings, or because the walls are made of materials that make it impractical to add windows). They suspend 2l soda bottles filled with a water/bleach solution from the ceiling, with the open tops poking out into the daylight. Sunlight refracts off the water in the bottle and turns it into a "lightbulb" that has been measured as supplying illumination comparable to a 50w incandescent bulb.

(Thanks, Phil!)



        1. Seeing as it is not a strong solution and that bleach is used in water purification drops and is pretty close to what is used in pools I really doubt anyone would go blind from this.  2 liter soda bottles are extremely rugged too.  Not sure what you are imagining but I don’t think they’ll spontaniously leak or explode.

        2. Ever been swimming in a chlorinated pool? Same concept. It doesn’t take a high concentration of bleach to keep water clear/sanitary.

    1. “Filled with bleach” is not the same as a teaspoon of bleach.It’s only in the wearer to prevent bugs and algae. 

    2. Nothing ; since bleach is not corrosive to plastic. Sarcasm or “wit” on the other hand are often destructive for any human endeavour.

  1. This reminds me of those prisms that boats used to embed in their decks to illuminate the inside.

  2. i’ve seen that trick before, super clever.  i wonder what the bleach is for — to keep the water clear, maybe?  places like favelas are where the ingenious ideas of the future are going to come from.

      1. As has been said, two or three days in and UV has completely broken down any chlorine.  Bleach is not diffusing the light, it is simply sterilizing the contents of the bottle to prevent algae growth.

  3. I think there was a similar project in a refugee camp posted here a while ago. The bleach is preventing bacteria buildup, essentially keeping the water clear IIRC. There are obvious drawbacks for widespread use; the most obvious is of course that it requires the sun to be out. And we’re not just limiting the use to daytime, but also leaving it up to the weather – dim day, dim lights. 
    But for places around the equator this is a great project. The advantages to those who had to live inside cramped and dark shacks in the refugee camps were even more obvious.

  4. and who is paying for the sealant fot that big hole in the roof? is it moonsoon safe? I would love to see those “hackers” running aroung with pots under the drilled roof.

    1. And what’s amazing is that Cory’s memory seems to be getting weaker and weaker. Only three months between posts this time…..

      1. And what’s amazing is that Cory’s memory seems to be getting weaker and weaker.

        To be fair, he didn’t post it before, and very possibly didn’t read it.  And I’m not in any position to criticise anybody’s memory.

      1. When BB blogged the 2011 Phillipines ‘Liter of Light’ project,
        which is based the 2009 MIT Haiti ‘Solar Bubble Light’ project,
        which is based on this 2008 youtube upload  of Brazilian TV covering:

        Alfredo Moser who says he had the idea in 2002,
        BB actually did not use the word ‘inventor’ *. 

        Anyhow, it is cool to see the idea is so widespread ;)

        *Edit: BB wrote ‘developed by MIT’ though.

  5. The bleach is to keep biological growth down, to answer an earlier question, but hasn’t this already been featured on Boing Boing?

  6. Why did my log in change?  Yes, I am Paul R in meat space and on Yahoo!, but not the Paul R that posts here under that name.  This new blogging software Boing Boing is using is just as invasive as Facebook, if not more so.  Disqus is every bit as bad as our Boing Boing editors have been saying Facebook is, yet they use it.  This is not a development that encourages trust in integrity, now is it?

  7. I want to know where they’re getting film canisters – I haven’t seen a place that sells actual film in years.

    1. I wondered the same thing.  That said,  if the sole purpose of the canister is to protect the cap from UV degradation (as suggested in the video), it might do to simply paint the cap.

  8. Except bleach breaks down quickly in UV.  Though I guess if the bottles are sealed and you successfully chlorine-sterilized them algae won’t grow inside even after the chlorine is gone.

    My concern is the roof penetrations.  Nothing destroys a building faster than water and nothing screams “leak” like a dozen haphazard roof penetrations.

    1. Yeah, uh…I’m guessing that if you already live a corrugated-metal shack, having one more hole in the roof isn’t really a big diminution in your quality of life. 

      Besides, the bottles have sheet-metal flashings placed around them and the whole works is sealed up.    Actually looks pretty watertight to me.

  9. This is being done on a large scale in the Philippines and other countries around the world. Visit  http://isanglitrongliwanag.org/ to see what is happening in the Phils.

    Great idea – very practical and when you consider that electricity consumes a large portion of family income in many poor countries, being able to stop using power for about a half day is a significant saving for these people.

  10. Sorry to be a complete downer here, but in the long run this could be dangerous. The bleach itself wouldn’t be an issue. I watched both videos available and I couldn’t see a supporting bracket for the bottle. Since this is a two liter bottle I can guess there is less than two liters of water in the bottle and so each bottles weighs less than two kilograms. If what I’m guess  is right then the only thing holding these bottles up is putty and the friction of the plastic against the corrugated steel. This lack of support in an earthquake prone area (such as the Philippines) is a recipe for disaster.
    If a cheap metal bracket could be made and attached, maybe with four screws on either side of the bottle, this would be relatively safe.
    I am not an engineer. Someone else would need to do the calculations for how many screws over how much area could support the downward thrust of 2kg, but I think it could be done and not cost an arm and a leg.
    The water proofing isn’t really an issue. This is the same idea as the below deck glass prisms used in sailing ships and they were able to keep those relatively water tight — even in storms.

    1. I’m not so sure that a 2-liter bottle of water falling from 5-6 feet above your head would qualify as a “disaster” in case of an earthquake.  Worst case, someone gets dinged on the head, but that would likely result in a bruise and bump, not a concussion.  Weighed against the ongoing poor conditions that come from poorly-lit rooms, I would be the health benefits are way on the plus side for this simple techno hack.

    2. You sound concerned. 

      If there’s an earthquake big enough to bring the bottle down, the whole friggin’ roof is probably going to come along for the ride.  Whether you get conked on the head w/ 2kg of water in a rounded plastic bottle isn’t really going to matter a lot at that point.

  11. Very clever.  Would be useful in a shed or other outbuilding that doesn’t actually NEED electricity.  Or an artist’s studio, since it would provide cheap natural lighting in areas that need it.  Or any temporary shelter.  Could even be useful in “Tiny Eco Houses.”  I imagine with the right sealant it wouldn’t be much more to maintain than switching out the occasional bulb.

  12. I wonder if there would be a cheap way to funnel light from outside through tubing into the bottle.  Hanging lights would be a lot more useful, and the funnel itself could provide more security than simply having the bottle tops exposed.

  13. Here we have the 1st world version:

    Friend of mine had one in is kitchen in SF.  It really increased the light on the island during the day (all the windows were north facing & somewhat shaded)

  14. Here’s a timeline:

    2002 – Alfredo Mosers starts making solar bottle lights
    ~2008 – he is shown on TV, probably all over South America and beyond
    2008 – a video of him and the lights is uploaded to youtube.com
    2009 – some people from MIT see this video, apply it in Haiti, and upload another video (crediting the original video)

    2011- behold the Solar Bottle Bulb, applied in the Philippines,  “designed and developed by MIT students” ( according to http://isanglitrongliwanag.org/about-us/ )

  15. Now wrap some cheap indoor solar panels around half these lights to charge a few car batteries during the day – and you can keep some cheap 12V car lightbulbs going at night for free.

  16. For all the smart-assed naysayers who moved onto criticising the potential for roof leaks after their fears about the dangerous, scary bleach were dispelled: If you watch the reuters vid that was included in Maggie’s original post [http://boingboing.net/2011/07/19/soda-bottles-become.html] the guy making these builds them with corrugated iron attached to the bottle, so installation would be no more risky leak-wise than adding a vent or fan to the roof.

  17. I keep seeing this on the intertubes and I keep wondering why people seem to think it’s so brilliant.  Punch a hole in the roof, light comes through it.  It’s not like that’s a scientific breakthrough.

    1. Punch a hole in the roof and light does indeed come through. a beam of light that casts a small circle of light on the floor that moves during the day.


      The 3/4s of the bottle the extends into the room, with the water in the bottle scattering the sunlight into the room, providing even illumination despite the apparent movement of the Sun across the sky.

      Oh, and NO ONE mentioned the words, “scientific breakthrough”.

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