Date: Mon Apr 23 12:57:38 2007

Author: Michael Timmins

Subject: Re: Big, loud, impressive demos

Post:
I use approximately 1:1 by weight and then adjust until it "feels" right.

As far as disposal, I took about 100 lbs of it home for my kids to play with,
the crowd probably took about 25 lbs. The rest is still in the pool on the
loading dock drying out. I don't think I will try to reuse, too many
critters could be growing in there by now.

Mike

On Monday 23 April 2007, Sam Sampere wrote:
> I use a 2:1 starch to water by volume. What ratio do use??
>
> Thanks,
>
> Sam
>
> -----Original Message-----
> From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On
> Behalf Of Michael Timmins
> Sent: Monday, April 23, 2007 12:07 PM
> To: tap-l@lists.ncsu.edu
> Subject: Re: [tap-l] Big, loud, impressive demos
>
> I'll reply to several messages at once:
>
> I got my cornstarch from foodservicedirect.com. It was about $15/25lb
> bag
> plus shipping (3 bag minimum). You will need at least 100 lbs for a 3ft
>
> diameter by 6" deep pool. Sam's idea of checking with the campus
> kitchen is
> a good one.
>
> As far as mixing goes, add the water first. We used a couple of 6'
> 2x4's to
> stir it. If I do it again I may consider getting a paint mixer drill
> attachment. It took two people about 45 min to mix a little over 100
> lbs of
> cornstarch. Also, the stuff settles so if you do it before the show,
> you
> will have to remix before using. This is where I would try the paint
> mixer,
> the stuff at the bottom is real thick.
>
> I'm not sure what other powders would work as well as cornstarch but I
> suspect
> that clay might work pretty well.
>
> Mike
>
> On Monday 23 April 2007, Sam Sampere wrote:
> > Mike,
> >
> > How did you mix a baby pool full of the stuff?? I'm doing that exact
>
> thing
>
> > tomorrow and am wondering if you have better ideas?
> >
> > After they took their baggies, how did you dispose of the stuff??
> >
> > Thanks!
> >
> > Sam
> >
> > ________________________________
> >
> > From: tap-l-owner@lists.ncsu.edu on behalf of Michael Timmins
> > Sent: Mon 4/23/2007 11:00 AM
> > To: tap-l@lists.ncsu.edu
> > Subject: Re: [tap-l] Big, loud, impressive demos
> >
> >
> >
> > For our show this year, I filled a kiddie pool with cornstarch and
>
> water
>
> > and let one kid come down and walk on it. It went over really well.
>
> It
>
> > was the last demo so I announced that people could come down and take
>
> some
>
> > home in a zip lock bag. What a mess! The kids had a great time
>
> shoving
>
> > their hands in and playing with large globs of the stuff.
> >
> > Mike Timmins
> >
> > On Monday 23 April 2007, Scott Shelley wrote:
> > > Hi all,
> > >
> > > Our Chemistry department put on an impromptu outdoor demo show last
> > > year that included a host of impressive demos: The thermite
> > > reaction, igniting a hydrogen balloon, natural gas soap bubbles,
> > > sodium in water, among others.
> > > This year, I'd like to counter their demos with a series of my
> > > own. I have questions about a specific one I saw a few years ago,
> > > but please feel free to add suggestions to this thread.
> > >
> > > At a Summer AAPT meeting in years past (Sacramento, I'm thinking), I
> > > witnessed the following demonstration.
> > >
> > > A weighted 2-liter bottle was partially filled with liquid nitrogen
> > > and then sunk to the bottom of a barrel full of water. A few
>
> seconds
>
> > > went by and BOOM - a large volume of water was displaced in
> > > approximately three nanoseconds. There was an audible gasp from the
> > > audience. I've been talking about this demo ever since I saw it,
>
> but
>
> > > since we don't typically do large demos shows at Haverford, I've
> > > never tried it myself. I have a few questions about the safety of
> > > this demo, before I blindly test it out.
> > >
> > > 1. By what mechanism was the bottle sunk in the barrel? I want to
> > > ensure I design something that doesn't become a projectile.
> > > 2. Is it safe to do this demo in an industrial sized plastic barrel
> > > (i.e. a large cylindrical trash bin) or should I use a metal
> > > drum. If it's the latter, does anyone know where I can acquire one?
> > > 3. How much LN2 should I use?
> > > 4. Is this demo as surprising as I remember?
> > >
> > > Other ideas for spectacular outdoor demos would also be appreciated!
> > >
> > > Thanks very much,
> > > Scott Shelley.
> >
> > --
> > Mike Timmins
> >
> > University of Virginia
> > email: mat3q@virginia.edu
> > phone: (434) 924-6800
> > mail address:
> > 382 McCormick Rd
> > Charlottesville, VA 22904



--
Mike Timmins

University of Virginia
email: mat3q@virginia.edu
phone: (434) 924-6800
mail address:
382 McCormick Rd
Charlottesville, VA 22904


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