In article <1992Sep1.231416.12855@hplabsz.hpl.hp.com>
schediwy@hplabsz.hpl.hp.co m (Bic Schediwy) writes:

>There has been talk of using potassium nitrate as an oxidizer for
>slow flash mix.

>I have not used this mix but I can well believe that it is tamer than
>flash mixtures using perchlorates or worse yet chlorates. Although

Yes, a nitrate flash is slower burning than a perchlorate based flash
powder. It also has to be very finely powdered in order to work or
ignite with a fuse only. The slow burning is not always a drawback. If
one wishes to have a good, long lasting flash, then nitrates are
better than perchlorates.

>boric acid. Given this information it would be advised that anyone
>mixing the above mixture add 1% boric acid.

Always mix boric acid when using aluminum with nitrates. Barium
nitrate flash powder is known to have self-ignited. That would have
been prevented by the use of boric acid.

>>When making flashpowder, I use to ballmill the KNO3 and the S together,

>powder), it should be emphasized that an explosion risk does exist.

I also use sodium nitrate based flash powder, but no milling is
required. I simply mix relatively coarse Al (<100 um) with sodium
nitrate (about 0,5 mm) using about 10 % excess of the Al. The mixture
is about impossible to ignite with flame, even with a gas torch you
can heat a long time before it starts burning - so it is safe to
handle. A blasting cap is required to set the powder off and the
critical diameter is about 2 cm. I usually load about 100 gram
charges.

The above flash powder gives an long lasting fireball and a nice
mushroom shaped cloud of smoke. You can really see the bright fireball
rise, before it goes off. Also, the air is filled with aluminum
sparks. After the extremely bright illumination, it is hard to see
anything for a while.

>cheers...bic

ArNO
    2

Newsgroups: rec.pyrotechnics
From: arno@utu.fi (Arno Hahma)
Subject: Re: Flash Powder
Organization: University of Turku
Date: Fri, 9 Jun 1995 07:50:10 GMT

In article <tip-060695171944@gold.aichem.arizona.edu>,
Tom I Perigrin <tip@lead.aichem.arizona.edu> wrote:

>Flash powder can be set off by amazingly small amounts of static...   I
>forget the exact number, but I believe 20 microjoules is about right.  Note

That much will ignite flash for sure. Last time I saw flash devices
being tested for static sensitivity, the energies were in the order of
1 to 10 microjoules. The most sensitive flash ignited about 80 % sure
with the lowest available energy. Such flash was made of Ecka 5413
(i.e. "dark German") aluminium. 5413-flash is also the most powerful
and burns the fastest.

It coarse enough aluminium is used, the flash can take even half a
joule sparks. However, then the "flash powder" will no longer explode
anyway, but only burn like thermite.

>I'd have to think hard before deciding if I'd rather mix and use 1 pound of
>flash, or swim acrosst an aligator infested lake.

Hard decision ;). I think I'd still take the flash mixing.  Tie a
container at the end of a long rod, stick the rod out of a door, close
the door as much as you can and then shake.  If it blows up, you have
it on the other side of the wall and a few meters away from you. Just
make sure the door and the wall can take the overpressure and you are
pretty safe.

Another possibility is to use a powered mixer of some kind with a long
extension cord. Prepare for replacing parts ;).


ArNO
    2

Newsgroups: rec.pyrotechnics
From: arno@utu.fi (Arno Hahma)
Subject: Re: Pyro's work with. . (was: The infamous Astrolite/C-4)
Organization: University of Turku
Date: Thu, 22 Jun 1995 21:28:00 GMT

In article <tad1-2206950824100001@tad1.cit.cornell.edu>, Tom Dimock
<tad1@cornell.edu> wrote:

>Just a semantic nit, Gordon.  Pyro's work with low explosives, with
>the most powerful typically being flash powder.  Bombers are

I would like to add, that using tritonal, torpex, ANFO/Al or equivalent
for salutes is a LOT safer than flash powder and you need a lot less
for the same effect.  Therefore, high explosives can find use in
pyrotechnics as well, although people seldom make use of them.  That is
mainly because of problems with regulations, I guess.

Besides, TNT or TNT/Al/NaNO3 salutes make very nice fireballs, too ;).
And it's far cheaper than using flash.

ArNO
    2

Subject: Re: What is the most powerful manmade explosive other than nuclear?
From: glhurst@onr.com (Gerald L. Hurst) 
Date: Apr 12 1996
Newsgroups: sci.physics,rec.pyrotechnics,alt.engr.explosives

In article <4kluc0$72n@defiant.america.com>, "Lloyd E. Sponenburgh"
<lloyds@fiscalinfo.com> says:

>billn@PEAK.ORG (Bill Nelson) wrote:
>>In other words, it is theoretically possible to have an explosive that has
>>a very high Vdet, but produces mostly solid combustion products. As such,
>>it would do relatively little work.
>
>Now, Bill, I'm _NOT_ trying to get that old "flash detonates! No, it doesn't!
>YES! IT DOES!" crap started again, so just take this for what it's worth.
>
>Flash is a good example of such an explosive.  Pretty brissant (for something
>which is just a simple mixture) but it produces only solid products, which
>don't even make a very large smoke ball.  Not much product, and all solids
>which condense within a few inches of the fireball...  (elipsis intentional)

Are you sure that flash does not produce a large ball of hot gas and
that the products do not condense a little later? I have seen it
stated in this forum that detonation does not occur well because the
rarefaction of condensation follows too closely behind the reaction
front. I do not fully accept this theory, but it may be that 
condensation interferes with the production of a stable shock
front under the relatively high pressures associated with detonation.
However, I am less convinced that condensation occurs so easily in 
what we normally think of as an explosive deflagration. 

I personally do not understand how flash can produce a good boom 
without the mechanism of a large gas cloud. Given that flash has
little brisance compared with HE, its abiliity to do work must 
depend on a substantial delta PV. It seems to me that given a small 
P, V must be large. I am assuming that there is a relationship 
between work output and sound.

I am aware that the visual output is a small, very bright ball, but
I remember experiments with highly aluminized HE which gave
similarly small flashes but would ignite combustible materials
at great distances. Consider also that aluminized military explosives
give high values for air blast, cratering, trauzl block and ballistic
mortar tests.

Jerry (Ico)

From: arno@nic.funet.fi (Arno Hahma)
Newsgroups: sci.physics,rec.pyrotechnics,alt.engr.explosives
Subject: Re: What is the most powerful manmade explosive other than nuclear?
Date: 16 Apr 1996 13:00:57 +0300

In article <4km4ul$31l@geraldo.cc.utexas.edu>,
Gerald L. Hurst <glhurst@onr.com> wrote:

>Are you sure that flash does not produce a large ball of hot gas and
>that the products do not condense a little later? I have seen it

No, I am not sure. It probably does just that. Flash powder spreads
out a cloud of mostly unreacted, hot aluminium powder, 
that deflagrates or detonates in the air (and in the oxygen from the 
oxidizer; gas phase detonation). 

>stated in this forum that detonation does not occur well because the
>rarefaction of condensation follows too closely behind the reaction

It is not the rarefaction of condensation but that of reduced gas volume 
compared to the original volume of explosive. I.e. the products have a 
smaller particle density (and covolume) than the explosive itself. 

Besides, a solid phase detonation seems to require a molecularly mixed medium 
to proceed.  Flash powder does not contain one.

>Jerry (Ico)

ArNO
    2

From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: rec.pyrotechnics
Subject: Re: flash powder detonates??
Date: 16 Dec 1996 08:35:35 GMT

In article <32B4BDC0.632F@sepa.tudelft.nl>, Hugo
<913362@sepa.tudelft.nl> says:

>Quote from the rec.pyrotechnics FAQ:
>
> > Some mixtures, particularly flash powder, will detonate rather
> > than deflagrate (just burn) if enough is present to be self-
> > confining.
>
>Has nobody disagreed yet?  I thought the word 'detonation' official-
>ly means the sudden decomposition of a (high-order explosives) mole-
>cule, resulting in the formation of a huge amount of gasses without
>a redox reaction.  Flash powder can't possibly detonate, can it?
>And if an unconfined pile of flash happens to say "boom", it doesn't
>make flash a high-order explosive, does it?
>
>Some quotes from the Terrorist's Handbook:
>
> > Low order explosives do not detonate; they burn, or undergo
> > oxidation.
> 
> > Black powder, nitrocellulose, and flash powder are good examples
> > of low order explosives.
>
>Any comments?

Sure.  Who gives a flip what is in the tennybomber literature.  
Whether flash can or cannot detonate isn't going to be decided 
by anything those pulp fiction works have to say.

When a charge of unconfined flash blows someone's hand off, it 
will make little difference whether the reaction rate was truly 
supersonic.

Your definition of detonation is wrong.  A detonation is an 
explosive reaction in which the rate of propagation is higher
than the speed of sound in the unreacted medium.  In relatively
small diameters, flash probably does not detonate; it just
reacts darned fast and generates lots of pressure.  I suggest 
that at very large diameters, flash might well detonate, but 
there are knowledgeable folks who would disagree.  

There may be some who have run enough experiments to extrapolate
the limiting value of the reaction velocity of very fine flash.
There is no substitute for a good set of experiments.  Beats
the heck out of the Terrorists Comic Book.

Jerry (Ico)

From: murr@katie.vnet.net (murr rhame)
Newsgroups: rec.pyrotechnics
Subject: Re: Flash in the Past
Date: 6 Jun 1996 18:12:04 -0400

VxMentaTxV@aol.com wrote:

>Howdy.  From what I have read here, I understand that flash is pretty much
>too dangerous to even bother making.  What I want to know is, back when
>M-80's and the like were legal to produce, how did factories etc go about
>making them in large quantities if a gram or two is enough to take off a
>hand?

A gram or two to take off a hand is an exaggeration.  A gram or two is
enough to do some serious damage.  It could peel some skin.  It might tear
off some mussel and tendon.  A couple of grams might remove a finger.  Two
grams is not going to remove a hand.  With a bit of luck, two grams would
only scar and cripple a hand for life.  Hands are relatively tough.  Eyes 
are much easier to damage.

>Is there some kind of stabilizer that makes it less sensitive to
>friction and static? 

Yes and no.  

The flash powder used for salutes like M-80s is always very sensitive to
static electricity, friction and impact.  The flash powder in salutes used
for display fireworks often contains titanium to create a sparkle effect. 
The titanium makes the powder MORE sensitive to impact and friction. 
Titanium does not make the salutes louder. 

One the other hand, some theatrical flash powders burn much more slowly
than the flash powders used for salutes.  These "sparkle powders" are less
sensitive to spark ignition and designed not to explode in modest
quatities when unconfined.  This is a broad generalization.  Some
theatrical flash powders are extremely sensitive to sparks.  Theatrical
sparkle flash powders may be very sensitive to impact and friction and 
may still be set off by modest sparks.

Many of the formulas for fireworks stars are basicly solidified flash
powders.  The powder is bound together with materials like nitrocellulose
lacquer into a solid lump.  When in solid form, these formulas are much
more difficult to light and burn much more slowly than loose flash powder. 

>...or were they just REALLY careful?

Extreme precautions are taken when handling flash powder.  Even so, many
professional pyros have been injured or killed handling flash powder.  The
risks can be reduced but never eliminated completely.  A young lady was
killed by flash powder accident at a fireworks plant just last month.
Flash powder can be deadly even under the best of circumstances.

>I have heard the procedure "diapering", what is that?

Diapering is done by placing the chemicals is separate piles on a large
piece of paper.  The corners of the paper are gently lifted one at a time
so that the piles of chemicals are gently rolled and tumbled into each
other. 

>Is flash really so unstable that mixing a few grams in say a zip-lock bag
>is a recipe for learning to type with stumps?  Of course the zipper part
>would probably grind up a few particles huh? 

Flash powder and a common zip-lock bag would be a bad combination.  Most
plastics can generate static sparks.  A spark to small to see or feel can
set off flash powder. 

>Please understand that I have no inclination to try making it, just very
>curious about this stuff that seems to set off safety alarms in the
>experts here... 

There are several reasons why flash powder sets off alarms.  First off is
the inherent danger.  Flash powder burns much more fiercely than black
powder.  It's also very easy to set off by accident.  Flash powder has
probably killed and maimed more skilled pyros than any other material. 
Flash powder is not a good first project for a new pyro...  If you have to
ask about flash powder, you probably should not be working with it. 

On the other hand, flash powder is somewhat boring to the more skilled
pyrotechs.  The main use for flash powder is to make a bang.  As fireworks
skills go, making a bang is pretty trivial.  The craftsmen are much more
interested in more difficult tasks like making good colors or shells that
fill the sky with lights. 


              murr rhame  /\/\ |_| |~ |~  murr@vnet.net
               Show-Fire special effects mailing list.

From: arno@antares.utu.fi (Arno Hahma)
Newsgroups: rec.pyrotechnics
Subject: Re: dynamite vs Flash power levels
Date: 5 Jan 1998 16:54:08 +0200

In article <34B04384.2316@IBM.net>, eddy  <eddy@IBM.net> wrote:

>Why is the reaction-front speed in chlorate-flash poorly-known,
>whereas the reaction front speed for PETN is known so accurately?

It isn't poorly known. Chlorate flash propagates about 500 to 2000 m/s
depending on type of ignition, confinement, density and composition.
Each set of variables produces its own propagation velocity. That's the
problem, if you can call it a problem.

The same applies to PETN as well. PETN detonation velocity is usually
quoted as the _maximum_ attainable, at highest possible density. That
is why the velocity spread is lower than for flash mixtures.



ArNO
    2

From: arno@utu.fi (Arno Hahma)
Newsgroups: rec.pyrotechnics
Subject: Re: flash deonation
Date: 21 Sep 1998 18:48:37 GMT

In article <6u494f$lq7$1@cougar.golden.net>, JW <jw_89@hotmail.com> wrote:

>A large number of people seem to think that various flash compositions
>can go high order when initiated with a blasting cap. No one seems to
>have come up with anything conclusive stating that they're wrong.

You might want to take a look at the following reference: Propellants,
Explosives, Pyrotechnics 21, 100-105 (1996). It is a study about
perchlorate-Al flash mixtures, which do not detonate.



ArNO
    2

From: gherbert@crl3.crl.com (George Herbert)
Newsgroups: alt.engr.explosives
Subject: Re: Could I mix Flash like this?
Date: 9 Jan 1999 00:02:08 -0800

Lindsay Hayden Greene <herbl@western.wave.ca> wrote:
>>There is always a chance of it igniting while you are screening, but
>>it will just go poof.  If it ignites in a film canister, it could blow
>>plastic shrapnel which is far more dangerous than an open burn.
>
>	But we must take into account that the plastic most film
>canisters are made out of is high-density polyethylene, which rips
>into harmless shreds when subjected to explosive shock.

Uh.  Having been the victim of some of these "harmless shreds"
before, I would like to point out that at sufficiently close
range they're still capable of producing wounds and probably
death should you be unlucky in fragment impact location.
My brother carried film cannister fragments in his hand
for some years (and may still have some there) and I have
had several less serious injuries.

That being said, film cannisters are probably the safest
"easy" containment you can get, and definitely easier if
you are, for example, considering taking it apart after
putting it together.


-george william herbert
gherbert@crl.com

From: ahahma@polaris.utu.fi (Arno Hahma)
Newsgroups: rec.pyrotechnics
Subject: Re: Starmines (reposted)
Keywords: starmines, stars
Message-ID: <1991Jul19.155051.26288@polaris.utu.fi>
Date: 19 Jul 91 15:50:51 GMT

In article <1991Jul17.233849.7805@ousrvr.oulu.fi> kempmp@phoenix.oulu.fi (Petri Pihko) writes:

>determines the reactivity and also sensitivity. A quite general rule is that
>compositions containing Al and KClO4 are _very_ sensitive to static
>electricity, moderately sensitive to friction and nearly insensitive to shock.

To give some more precise idea about the sensitivity:

Spark sensitivity: 0,1 to 10 millijoules, depending on the mentioned parameters
friction sensitivity: 4 to 12 kg load, BAM
shock sensitivity: 15 to 25 cm with 1 kg fallhammer, BAM

> ___. .'*''.*        Petri Pihko    kem-pmp@finou.oulu.fi kempp@tolsun.oulu.fi

ArNO
    2

From: ahahma@polaris.utu.fi (Arno Hahma)
Newsgroups: rec.pyrotechnics
Subject: Re: Recipe for nitrate-based flashpowder!
Keywords: flashpowder, nitrate, safe
Message-ID: <1992Sep9.170823.26792@polaris.utu.fi>
Date: 9 Sep 92 17:08:23 GMT

In article <1992Sep1.231416.12855@hplabsz.hpl.hp.com> schediwy@hplabsz.hpl.hp.com (Bic Schediwy) writes:

>There has been talk of using potassium nitrate as an oxidizer for
>slow flash mix.

>I have not used this mix but I can well believe that it is tamer than
>flash mixtures using perchlorates or worse yet chlorates. Although

Yes, a nitrate flash is slower burning than a perchlorate based flash
powder. It also has to be very finely powdered in order to work or
ignite with a fuse only. The slow burning is not always a drawback. If
one wishes to have a good, long lasting flash, then nitrates are
better than perchlorates.

>boric acid. Given this information it would be advised that anyone
>mixing the above mixture add 1% boric acid.

Always mix boric acid when using aluminum with nitrates. Barium
nitrate flash powder is known to have self-ignited. That would have
been prevented by the use of boric acid.

>>When making flashpowder, I use to ballmill the KNO3 and the S together,

>powder), it should be emphasized that an explosion risk does exist.

I also use sodium nitrate based flash powder, but no milling is
required. I simply mix relatively coarse Al (<100 um) with sodium
nitrate (about 0,5 mm) using about 10 % excess of the Al. The mixture
is about impossible to ignite with flame, even with a gas torch you
can heat a long time before it starts burning - so it is safe to
handle. A blasting cap is required to set the powder off and the
critical diameter is about 2 cm. I usually load about 100 gram
charges.

The above flash powder gives an long lasting fireball and a nice
mushroom shaped cloud of smoke. You can really see the bright fireball
rise, before it goes off. Also, the air is filled with aluminum
sparks. After the extremely bright illumination, it is hard to see
anything for a while.

>cheers...bic

ArNO
    2