Date: Thu, 26 May 2011 22:36:09

Author: Urs Lauterburg

Subject: Re: Fish Tank



Thank you for the pointer. It makes sense. I can't see that this
substance is overly aggressive though. A bit of alcohol with a bit of
resin should not degrade the aquarium seals. Salt is worse, but just
for a few days it should be fine too. I might try sugar the next
time. Generally water is technically considered to be a difficult and
rather strong corrosive substance to handle.

Yes, there are indeed many kinds of silicones. I will have to ask my
coworker what kind he used for the fix. He ordered it specially I
think and he has quite some experience with sealing glass tanks from
his prior job.

... well milk and alcohol...



>The mastic you use is essentially the same as pine-sol, which is pine resin
>dissolved in alcohol,
>Michael Thomason, Director of Physics Learning Laboratories
> University of Colorado Boulder Department of Physics
> 303-492-7117
>-----Original Message-----
>From: [] On
>Behalf Of Urs Lauterburg
>Sent: Thursday, May 26, 2011 1:01 PM
>Subject: Re: [tap-l] Fish Tank
>I just went through this exercise. Our longtime shallow aquarium
>which I use for various optical demos like refraction, Tyndall effect
>etc. began to leak after many years of use. In fact the aquarium
>consists of a metal frame made of thin rectangular steel profile and
>originally, the glass was sealed by putty. It lasted amazingly long.
>We have now taken out the glass and replaced it with new one. In fact
>my coworker used silicone to seal the glass this time. The leak test
>still has to be made next week!
>Let's see if it leaks and if not, how long it will last. We may be
>going back to putty later on Actually, the reason why I wanted to
>keep this particular tank was, because I could not find a similar
>shape commercially. Its size is about 60 x 40 x 10 centimeters and
>ideal to visualize light beams. To make a laser beam visible I take 2
>or 3 grains of Mastic, which is the resin of the mastic tree
>I would dissolve the little pieces making up 1 to 2 grams in about
>4ml of alcohol and later pour it into the distilled water in the
>tank. The particles stay suspended and the water stays almost clear
>with a faint bluish taint due to the Rayleigh scattering. The mixture
>is not aggressive at all.
>What probably caused the leak was the demo where we would create a
>strongly bent light beam by filling a layer of solid salt on the
>ground of the tank. The mixture has to sit for a few days in order
>for diffusion to make a nice and even gradient for the index of
>Time will tell if silicone or putty wins ;-)
>Regards from the Swiss demonstrator with a new fish tank.
>Urs Lauterburg
>Physics demonstrator
>Physikalisches Institut
>University of Bern
>>My 40 gal. fish tank has sprung a leak for the second time. Anyone
>>know of a glass epoxy that will stand up to the Pine-Sol that I put
>>in it for optics demos??
>>U of Iowa

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