On Sat, 20 Apr 2013 07:59:04 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

" fired this volley in news:dea88c27-
:

So does anyone know what was used

Dan,
One of my infrequent jobs is to do for-pay forensic studies of fireworks
accident scenes, in order to find the cause(s). Part of that involves
doing chemical analyses on the various combustion residues in the area.

In this case, I cannot analyze them chemically, but can still evaluate
the flame-front velocity, the fireball size, the smoke output, and the
smoke color for ideas of what the substance was.

The burn rate and fireball size were consistent with a potassium nitrate
or potassium perchlorate-based composition that was fairly fast-burning
under the degree of containment afforded by the pressure cookers. Keep
in mind, they won't hold much more than about 60-80psi before the break
their little lock tabs, so the pressures wouldn't be as high as they
would be in a 'real' bomb casing.

Black powder is fairly scarce these days for casual purchases. It's
expensive, too. But it can pretty easily be homemade, and can be made to
a quality as good as Goex's shutzen powders.

The BP substitute, Pyrodex, _claims_ to be low-smoke, but in fact makes
as much white smoke as black powder does. Pyrodex is potassium
perchlorate-based, and burns roughly at the same speed as black powder,
with about the same explosive force, volume-for-volume (NOT weight-for-
weight.) Pyrodex is MUCH less dense than BP, which is 1.7g/cc solid
density, and about 1.0g/cc mass density in granulated form.

So... a 6-quart pressure cooker would hold as much as 12 pounds of Black
powder. That would make quite a 'whack', suitably contained.

You'll also note that the containment failed before the lid fragmented.
See the distorted lid pictures. The shrapnel injuries must've been the
result of shards of the pot base, or the nail-shot additions to the load.

There are a couple of other mixtures, pyrotechnic in nature, that would
give the same basic profile of fireball, smoke, and propulsive force.

One thing for sure... it was NOT "flash powder" (the stuff that kids so
often try to collect from firecrackers to make bigger ones). Flash
powder is so fast-burning under containment as to be categorized for
storage and transportation as a high explosive (although it's not
really). It also makes a small and compact, bright-white fireball.

LLoyd

Lloyd, don't you think they know by now exactly what powder(s) was
used? BP leaves so much residue that no one who's used it could miss
it. And the others must leave enough chemical residue to clearly
identify them, right?

I assume so, although chemistry is something about which I know next
to nothing. My guess is that we'll hear pretty soon what they came up
with in the lab -- if it hasn't come out already, and I just missed
it.

--
Ed Huntress