ISEN-ASTC-L is a service of the Association of Science-Technology Centers
Incorporated, a worldwide network of science museums and related institutions.
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Jay,

Many museums have this kind of exhibit in various forms. I believe the 
Pacific Science Center had one with their traveling Science Carnival and 
they also had one with rotating tubes in which pool balls dropped 
through fluids of various viscosities.

I have built this kind of thing using mineral oil, which is probably the 
cheapest thing you could find to use in this exhibit. Glycerin seems to 
be another possibility. But the most often used product seems to be 
silicone oil. It's not cheap, about $50+ a gallon depending somewhat on 
viscosity and quantity you buy.  If you need several viscosities you can 
buy a quantity of a low viscosity (say about 20cSt) and a high viscosity 
(say about 30,000) and mix them together to arrive at intermediate 
viscosities depending on proportions. Silicone oils seems to have very 
good long term stability and will not support organic growth. Also, 
according to its MSDS it is relatively safe. If it spills its biggest 
hazard seems to be that it is slippery.

You can check with ClearCo Products 
(http://www.clearcoproducts.com/standard_pure_silicones.html) if you are 
interested in checking out silicone oil. It's a family run company - it 
may not be the cheapest, but you'll talk to one of the owners if you call.

Joe Ruggiero
www.theexhibitguys.com

Jay Higgins wrote:

> 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've been playing with an art piece for an exhibit where air 
> bubbles form at the bottom of a tube and float up through the clear 
> oil.  I can't remember where else we've seen this, but we love the 
> effect.
>
> After playing with some small amounts of food grade lubricating oil 
> we've started looking for large amounts.  The trick is finding a clear 
> oil in different viscosities that won't break the bank.  Does any one 
> have experience with mineral oil or silicon oil?  Can anyone  
> recommend a retailer?
>
> Thanks,
> Jay
>

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