Wayne,
   I suspect that the propellant in the hairspray is a hydrocarbon such 
as propane.
   A propane-air mixture does not detonate; rather it burns rapidly like 
gunpowder.  This would provide a longer seismic pulse than the 
detonation of hydrogen-oxygen or acetylene-air mixtures.
Bob


Wayne Francis wrote:

> Just as an aside, some of these contraptions sound a little like my
> son's potato cannon. Along with the spark, it used Aqua-net hairspray as
> the volatile substance (would auto starter spray work?).  Pretty good
> bang to fire that potato.  They used PVC, but build one out of 2 inch
> steel pipe, give it a squirt, set it off with a sparker (they were
> experimenting with piezo, ie. barbeque striker).  Might work.
> Wayne Francis
> Ojai, CA
> 


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