white balloons + laser = safe lightshow?

I'm preparing laser visuals for some friend's concert, but unfortunately limited wall space above them performing (low ceiling) won't offer very much space (only a wide thin image) – so I had the idea of hanging an array of white balloons on the ceiling and targeting them with various colored lights from my 1.8W RGB laser (LaserWorld DS-1800). I've watched a few videos demonstrating laser on white balloons:

https://youtu.be/o7rKwDDfHsQ?t=21s
https://youtu.be/aTRVfKqG59M?t=2m3s

– but the question that wasn't answered in those videos, is: just how safe is the refracted/diffused/scattered laser light (coming off?) the balloon? Is there any eye danger or does it get so broken up, it's no problem from 1+ meters away?

Any explanations or thoughts would be most helpful, thanks!

+ didn't find an answer searching the forum, but of course @zoof's creation is way cooler!

To comply with the rules about exposure, assuming your in the US, we would have to make a series of measurements. The first part would be the power and divergence of the laser , how reflective the average inflated balloon is(with 32 or so trial measurements), and what the angle of scattering is off of the balloon at a known distance. Then we would have to check the uniformity of the scattering. On top of that, we would need to be assured your not hitting the neck of the balloon, and know how far it is from the eye of an audience member at the closest point of approach. Short answer is NO until you actually make measurements with proper equipment. Then there is the whole quality control process on top of that...
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Can it be done, yes! Do you have the sensitive, accurate power meter with a 7 mm or 25 mm aperture you will need?, well... Probably not... Am I trying to be an Ass, no, just considering what it would take to do it right...
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Is it safe under some conditions, probably, if your far enough from all the balloons....
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Steve

Thanks for the quick reply. I'm based in Europe and unfortunately do not have said measuring equipment. The laser's max R/G/B power measures 450mW/150mW/1,100mW – which I'm controlling via programming, already plan to use as minimal settings as possible. The distance of projector to said balloons, is anywhere from ~7 - 15 feet away (guessing, haven't measured space). Projector is on ceiling, above everyones head, from where audience would stand, pointing towards the balloons on ceiling above the band.

You're right about this being a potential no until it could be correctly measured. I suppose I was hoping for a general 'beyond X distance from eye at Y strength, it would be ok'. Of course angle, reflection of balloon play important roles that can't be so easily answered here.

Where in Europe? I imagine in the morning some of our European friends who do legal audience scanning might chime in and help you out... Some one may be nearby. Some of them have the tooling to do the measurements. Problem is the balloons are batch specific... I have no idea what I'd get if I stop on the way home and buy a bag of white balloons...

Steve

Switzerland – and yeah, really hope some of them can and will. The laser beam wouldn't be crossing anywhere near the audience (it's out in front of them).. it would/should only be an issue of the refracted light. And true, balloons are batch specific. Today I visited a store that ONLY sells balloons and got various sizes of their least shiny, white ones = there's surely variance, but from fairly high quality source. Something else I could/should consider, is blowing them up less than full, perhaps making it less reflective when the surface isn't stretched so tight? The other thing I'm wondering, is if balloons and laser are relatively at the same height on ceiling (laser just a bit lower) – is the problem less of an issue if only letting a laser dot (likely sending single beam point) hit the bottom of them rather than side... of course something to test in controlled environment. But I'm guessing that when the laser hits the balloon, and only 'fuzzy' or blurry light comes off it (no focused points) – then that could be a sign there's enough refraction taking place? .. not searching for excuses, just curious about the visible qualities of safe laser light.

As an alternative, I'm also playing with using a short throw projector = no safety issues at all.. just such a dull light source in comparison!

Do you have an iPhone?

If so, download the following App's... 'Laser NOHD' and 'Laser Safety'

Both of which have been programmed by James Stewart at Laservisuals.

'Laser NOHD' should give you a good start at knowing at what distance your laser becomes eye safe for an accidental exposure... 1.8Watt Laser with a 1mr divergence becomes briefly eye safe (for 0.25 sec) at a distance of 300 mtrs.

Please note that these rough calculations are only a start and shouldn't be relied upon. There is no substitute for having the proper equipment and doing the 'real world' calculations.

Hope this helps.