# Of Catburglars and Lasers **URL:** \ **Category:** Factual Questions\ **Created:** [October 22, 2013, 11:41am UTC](https://boards.straightdope.com/t/of-catburglars-and-lasers/671921 "2013-10-22T11:41:44Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [October 22, 2013, 9:42pm UTC](https://boards.straightdope.com/t/of-catburglars-and-lasers/671921/21 "2013-10-22T21:42:17Z")
> [@The Great Sun Jester](#): > > Cigarette smoke? Well, aside from setting smoke alarms off and telling a bunch of Cub Scouts to light up, I don’t see anything wrong with that… ---
**Author:** ![dstarfire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dstarfire/32/5762_2.png) [@dstarfire](https://boards.straightdope.com/u/dstarfire)\ **Post date:** [October 24, 2013, 10:04pm UTC](https://boards.straightdope.com/t/of-catburglars-and-lasers/671921/22 "2013-10-24T22:04:23Z")
Back in high school one of my classmates did a presentation on lasers and he used a simple spray bottle with water (you can probably find a small one at your local dollar store) so we could see where the beam was. You could even give spray bottles to the scouts, since it’s just water. ---
**Author:** ![Valgard](https://avatars.discourse-cdn.com/v4/letter/v/7feea3/32.png) [@Valgard](https://boards.straightdope.com/u/Valgard)\ **Post date:** [October 24, 2013, 10:16pm UTC](https://boards.straightdope.com/t/of-catburglars-and-lasers/671921/23 "2013-10-24T22:16:52Z")
> [@dstarfire](#): > > Back in high school one of my classmates did a presentation on lasers and he used a simple spray bottle with water (you can probably find a small one at your local dollar store) so we could see where the beam was. > > You could even give spray bottles to the scouts, since it’s just water. He tried that, see post #6. ---
**Author:** ![Capt\_Kirk](https://avatars.discourse-cdn.com/v4/letter/c/779978/32.png) [@Capt\_Kirk](https://boards.straightdope.com/u/Capt_Kirk)\ **Post date:** [October 24, 2013, 10:52pm UTC](https://boards.straightdope.com/t/of-catburglars-and-lasers/671921/24 "2013-10-24T22:52:32Z")
You may be able to get permission to turn the fire alarm off. One of the live music venues I work in had the “wrong” kind of fire alarm installed and we could not use fog or haze. After many complaints from touring acts it was discovered the the Fire Marshall will let the alarm system be off for the evening. It requires a (cheap) permit and there are some rules but they let us fill the venue to capacity(1750 ppl)and run shows with no noticeable change. I would ask the Fire Marshall first and then the school, couldn’t hurt. Good luck **Capt** ---
**Author:** ![ducati](https://avatars.discourse-cdn.com/v4/letter/d/cc9497/32.png) [@ducati](https://boards.straightdope.com/u/ducati)\ **Post date:** [October 25, 2013, 4:36pm UTC](https://boards.straightdope.com/t/of-catburglars-and-lasers/671921/25 "2013-10-25T16:36:08Z")
A school cafeteria should be large and high enough not to concentrate fog from a machine. A small fan set nearby can create a breeze that will push the fog through the laser beams. Dry ice in a bowl on a table will spill over the bowl and table, creating a curtain of “smoke” to play with. If you can use a hotplate, boil water in a pot; the resulting steam is teeny tiny droplets, and if you wave the laser’s beam back and forth - in the dark - you’ll see them lit individually, and you can see a “slice” of the steam. Dry ice in a milk jug or similar gallon-sized container can create a smoke jet. Punch a hole near the top about 1/8" to 1/4" in diameter. Add crushed/broken dry ice, fill with hot water, and screw on the cap. You will have a smoke jet that goes out 3-4 feet. Do this in the dark about 30 feet from the kids. Give one or all a laser, and have them find the fog by sweeping the beam around. If you really want fog that won’t rise, look up fog cooling projects on the interweb. ---
**Author:** ![Bone](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bone/32/407_2.png) [@Bone](https://boards.straightdope.com/u/Bone)\ **Post date:** [October 25, 2013, 5:53pm UTC](https://boards.straightdope.com/t/of-catburglars-and-lasers/671921/26 "2013-10-25T17:53:29Z")
> [@Pixel\_Dent](#): > > Five or Six years ago Mythbusters tested this and decided something like to see the beam you had to have so much powder or mist in the air that it stopped the beam. The effect you see in the movies doesn’t happen in reality. The laser from my pistol is visible at the indoor range on an intermittent basis. So…you could fire few hundred rounds of ammo in a confined environment first? ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [October 25, 2013, 5:56pm UTC](https://boards.straightdope.com/t/of-catburglars-and-lasers/671921/27 "2013-10-25T17:56:46Z")
> [@Bone](#): > > The laser from my pistol is visible at the indoor range on an intermittent basis. So…you could fire few hundred rounds of ammo in a confined environment first? Make sure it’s lead-free ammo. Or at least Total Metal Jacket. 😃 ---
**Author:** ![Unintentionally\_Blank](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/unintentionally_blank/32/5418_2.png) [@Unintentionally\_Blank](https://boards.straightdope.com/u/Unintentionally_Blank)\ **Post date:** [October 26, 2013, 3:33am UTC](https://boards.straightdope.com/t/of-catburglars-and-lasers/671921/28 "2013-10-26T03:33:44Z")
Found a reasonable compromise. We’ve got an ultrasonic mister which’ll do, plus, in a clear vessel you can show the laser curve in water. two for the price of one! [Previous page](https://boards.straightdope.com/t/of-catburglars-and-lasers/671921.md?page=1)