ISEN-ASTC-L is a service of the Association of Science-Technology Centers
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When we had Strange Matter here a couple of years ago, I used Epsom
Salts (Magnesium Sulphate) to form crystals rapidly. 

We dissolved as much of the salt as we could in water warming on a
hotplate, and then dropped the solution on the surface of an old
fashioned overhead projector. The crystals formed instantaneously and a
whole room had a great view on a screen as the crystals formed.
Afterwards, you could lift the transparency sheet and pass it around and
to see the crystals up close.

We were planning to use this as a floor demo but keeping the solution
hot enough was a problem - we were very concerned the public might get
burned. It worked well in volunteer training, and I could see it working
in a classroom. 

-----Original Message-----
From: Informal Science Education Network
[mailto:[log in to unmask]] On Behalf Of Jane Snell Copes
Sent: Thursday, August 16, 2007 10:33 AM
To: [log in to unmask]
Subject: Re: Quick Crystals

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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*****

I would avoid naphthalene either in solution or sublimed and 
recrystallized.  Here's a link to MSDS, indicating moderate health 
and flammability hazard.  OSHA exposure limit is 10 ppm, which is 
quite low.  If you can smell it, you're likely above the limit. 
http://www.sciencestuff.com/msds/C2149.html

Sodium acetate and sodium thiosulfate 5-hydrate are both less toxic 
and can actually be reused.  That's my 2 cents' worth.  Do you 
realize computer keyboards no longer have a cent sign?  Jane
-- 
Jane Snell Copes	  Science Outside the Box    651-357-3316 (cell)

Science Outside the Box is a tiny business that celebrates the 
scientist in every one of us.  I am a writer and teacher, and I have 
fun with science every single day.  I'm especially fond of designing 
classes and science magic shows for kids and parents.

"To be an inventor, you need a good imagination and a big pile of 
junk."  Edison

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For information about the Association of Science-Technology Centers and the Informal Science Education Network please visit www.astc.org.

Check out the latest case studies and reviews on ExhibitFiles at www.exhibitfiles.org.

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