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Jon.
all the standard smokes are charred oil or similar and will make deposits.
a few options which we've used in similar situations.
1) use water based fog instead ( an ultra sonic type, as used in small indoor ponds) -if your labyrinth is small enough or a larger unit from an air-conditioning humidifier system if it needs more. You could try this in your current system by the sounds of it. worst case is you'll get some condensation on the mirrors, which will distort the light path.
2) put a small "line lens" - ( a glass/plastic cylinder of a few mm diameter) in front of the beam to get it to form a vertically spreading beam. Angle the whole laser down a little if needed. as the beam goes through the maze, it grazes the bottom of case - paint that white to show the beams path.
draw backs.. you'll need to fiddle with finding fitting the lens ( or by a unit with a line lens fitted - available for just these sorts of jobs) -I'd go to the hardware shop and by a cheap laser level ( builders level) these are about $50 and have a line lens to help people like me get things straight. ALSO as the beam is spreading as it travels it gets a little weaker... but it will go the distance.
3) put the entire thing in water. build a tank, fill it with water.. and a drop of milk ( for a short test) or a drop of soluble oil or a few drop of dettol liquid antiseptic ( which has a few compounds dissolved in its mildly alcoholic mix. Add a few drops to water and these come out of solution making a very stable fine suspension that scatters light in a very suitable way for these demos. Your mirror adjustments could come down through a clear lid/cover making it simple to keep the tank watertight.
hope this helps, if anything seems promising but unclear let me know.
cheers
Stuart Kohlhagen
Manager Research and Development
Questacon
the National science and Technology centre
Canberra
Australia
-----Original Message-----
From: Informal Science Education Network on behalf of Jon Haavie
Sent: Fri 21/08/2009 5:52 PM
To: [log in to unmask]
Subject: Laser, mirrors and smoke! How to make it work?
ISEN-ASTC-L is a service of the Association of Science-Technology Centers
Incorporated, a worldwide network of science museums and related institutions.
*****************************************************************************
Hi,
We have made a sort of laser labyrinth, with adjustable mirrors and
smoke. The smoke is used in order for the users to see the laser, the
mirrors are used to direct the laser throgh the labyrint. But we've
hit a couple of snags that have stopped the development. The mirrors
get covered with residue form the smoke, so I had to wipe them off
every day or so. Even though we mounted an extraction tube on the
table, so the smoke would be sucked out. I know there's different
kinds of theatrical smoke, but I've tried a few and they all seem to
have the same problem.
Any thoughts?
Best regards,
Mvh. Jon Haavie
----------------------------------------------------------
Prosjektutvikler
Vitensenteret, Norsk Teknisk Museum
http://www.tekniskmuseum.no/
Kjelsåsveien 143, N-0491 Oslo, Norway
Tlf. +47 22 79 60 77, Mob. +47 93 87 77 63
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