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Popping Balloons for a School Experiment. Which Laser is Best?

zilali

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Hello all,

I am a PhD student in chemistry/nanoscience and I am hoping to do some outreach in schools to teach science. I have proposed to my university that I do an experiment with the children looking at light and energy. My idea was to take a sufficiently powerful laser pointer and use it to pop various balloons of different colours. The children could guess and then time which coloured balloons would pop faster than other (i.e black vs white). I could then use this to explain absorbance of light/colour/energy and various other things.

A few quick questions. I have a read a bit online but I am still unsure as to what power/. wavelength would be best for this experiment? I have a thought that 100 mw green would be good but perhaps this is too powerful ( I don't want the balloons to pop instantly)

Also any idea where I could purchase such a laser? I have a budget of £150/ $220 but will also need to buy 8x pairs of safety glasses. Is this enough money?

Thanks
 

marcuspeh

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Will everyone be wearing laser safety goggles? If not, i would recommend you not to do that. You might end up accidentally causing your students to be blind.
 

Pi R Squared

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I would go with something much more powerful in a violet 405nm or a blue 445/450nm if you want to pop different color balloons, especially if you don't want them to have to be real close to the laser, or if you want to pop a row of balloons, you can always unfocus it slightly if it pops the balloons to fast, but the more powerful the laser the more dangerous it is, so extreme caution is called for. I have lasers that can pop any balloon but they can also burn stuff across the room or leave scorch marks on the wall or burn you if you passed your hand in front of it so I am not sure what power is best for you. Your budget is enough if you buy cheap safety glasses. Most people here spend $40-$50 or more for one good pair and then some additional cheap ones. Cheap safety glasses $10 or less will work, just make sure no one takes a direct hit in the eye. Maybe get a tripod with a clamp to hold the laser, there have been accidents before where a laser rolled off a table or when someone dropped the laser, also be aware of any reflective surfaces or mirrors in the room.

Alan
 

zilali

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Thanks for the advice. And yes safety is a must. I plan to buy safety glasses for all involved and I plan to create a setup where the laser is clamped down so it can't roll of any take out a classroom full of eyes
 

SteveT

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I don't think your budget will stretch far enough given that you need to purchase 8 pairs of goggles alone. A trusted brand, such as EaglePair, will cost around £28 (you could probably agree a bulk discount) - Link is for glasses suitable for a BLUE laser (as PI R has said, best bang for buck when it comes to burning within the visible spectrum)

http://www.survivallaser.com/Eagle_Pair_190540nm_8002000nm_Laser_Safety_Goggles/p556088_4768519.aspx

You can opt for cheaper pairs and there are plenty on ebay but please check the OD spec carefully.

Now for the laser itself, you'll probably want something in the 750mw + range if you want to pop balloons from distance - there are plenty of custom sellers/builders on this forum who can build a laser to your specs - search function (the bottom one) is your friend here.

PS. I'm assuming you're from the UK - if you post your rough location there may be a member nearby willing to loan you their laser; unless of course you want to keep one for yourself after the experiment ;)
 
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Teej

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I would like to point out that the color of the beam and the color of the balloon are related, in that if you pick one color for one, it can dictate your choice for the other.

Generally, the safest balloon color is black, as it absorbs the most regardless of the laser color, etc...and, it reflects less....and is typically the easier to pop/can be popped at the longest distances. Balloons for retirement/over the hill or Halloween type events are good sources.

:D


The safety glasses are not as much because you are likely to have a laser that rolls over and strafes the young orbs, as you are to have the beam hit the balloon (reflective in lighter colors for example, plus, when inflated, even black can be reflective, etc...) and/or what's behind the balloon, and ricochet back at your audience/you, etc.

Hitting even a steel screw head on a wall's light switch for example can send the beam right back atcha.

If the kids watching are close to the "dot", the intensity of the dot is very very bright, and, it can be akin to watching someone weld, if they are not protected by distance/shielding/PPE.


Some wavelengths (IR and UV, which pop things very well, don't induce a blink when they hit an eye...so damage starts, and, has more time to continue.

Green (532 nm for example) is typically the most visible for a given power rating for example, but I find for a visible beam, I like BLUE (445 nm) for a lot of burning power, primarily because a high watt 445 nm is less expensive than the same wattage in say green...

...and a blue laser is just so cool. They can be focusable too, so, from a demonstration standpoint, you can dial the beam to a wider rectangle that will not hurt things as a "safety" as well as demonstrate the way the light is concentrated and rendered more coherent as you focus it tighter and tighter until the focused point is so concentrated that you can set the balloon on fire (even better than a mere POP)

:eg:
 
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USAbro

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Will everyone be wearing laser safety goggles? If not, i would recommend you not to do that. You might end up accidentally causing your students to be blind.
I think he mentioned buying his students goggles.
 

NarwhalZ

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I recon 100mw should be enough. Also you can check out my small review on the Sci-fi lasers SF501B 100mW 520nm. Sci-fi is a great place to go. Also goggles should be needed with such a laser. May I also include that you bring a few matches just to show off ;)
 

Pi R Squared

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LOL yes bring matches, also burning through a plastic DVD case really impresses people too. You will have all those kids wanting their own laser. I disagree on 100mW although yes 100mW can burn stuff but you said you want to pop different color balloons, not just black ones. I would go with something class 4 as long as you can be careful with proper safety. Blue is best power for the price 445nm/450nm. Or a 500mW+ 405nm is great except that 405nm is at the edge of the visible spectrum and barely visible. I almost forgot, you will have to include batteries and a charger in your budget too, so your budget is borderline or a little light.

Alan
 
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zilali

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Hello all,

I found this laser on sci-fi lasers which is only $85 for 1W @ 445 nm. This seems remarkably cheap but also maybe an overkill in terms of power. Can anyone recommend it?

SF501B 445nm Blue
 

NarwhalZ

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Hello all,

I found this laser on sci-fi lasers which is only $85 for 1W @ 445 nm. This seems remarkably cheap but also maybe an overkill in terms of power. Can anyone recommend it?

SF501B 445nm Blue
Sci fi are one of the most trusted laser companies out their. :) Also 1W might be overkill for popping balloons as they should pop instantly on pretty much all colored balloons I would not go over 300mW. Divergence is also a good thing to talk about in the lesson.
 
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ixfd64

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As an alternative to goggles, you could consider using some sort of safety screen. One of the chemistry professors put on a demonstration involving a high-powered blue laser during my freshman year of college, and he did not pass out goggles to everyone in the lecture hall.
 

olympus mons

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You could also ask a trusted member here to make you a laser if you payed for all the supplies I don't think that would violate laser laws Sales. An underdiven m140 blue diode and driver in a 501b host should be under $100 easily and you could set the power output to what you are looking for. you can even run an xdrive buck driver with a single 18650 battery rather then the normal 2 x 16340's to keep the power output low. this way after your demonstration you can still have a fun personal laser with more power. Just a thought.
I own a Sci fi and Eitan makes a great product but the wait can be a month or more plus international shipping cost amd time is a factor In the event you need this sooner than that. Good luck I hope you inspire some kids to take an interest in science. The United States has a decline in young people pursuing science degrees compared to other nations.
 




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