From: pjac@ruc.dk (Peter Jacobsen)
Newsgroups: rec.pyrotechnics
Subject: Recipe for nitrate-based flashpowder!
Keywords: flashpowder, nitrate, safe
Date: 31 Aug 92 19:08:31 GMT
Organization: Roskilde Universitetscenter, Danmark

One of the frequently asked questions in this newsgroup is "How do I make
flashpowder" ("big booms" and the like).  The recipes for flashpowder vary,
from widely used perchlorate-formulas like the 70:30 Potassium perchlorate
(KClO4) and Aluminum (Al) to very dangerous mixtures of Sodium or Potassium
chlorate (NaClO3 or KClO3) and Al and sometimes even with Sulphur.

For long time ago I was looking for a safer, but still effective formula,
and today I always use the following composition:

        8 wt.parts Potassium nitrate (KNO3)
        3 wt.parts Sulphur (S)
        4 wt.parts Aluminum dust (Al)

Originally I found this formula in the newsletter "American Pyrotechnist",
and later I saw it reprinted in "The Poor Man's James Bond, volume 1".

This nitrate-based flashpowder is not a detonating kind, but rather a fast-
burning and very energetic, modified black powder, that meets the two most
important demands:

1) It is relative safe

It does not contain chlorate or perchlorate. It is not sensitive to acidic
impurities (as in the Sulphur). It is fairly chock resistant (I have tested
several batches and have never been able to set off a sample, even when hit
with a hard hammer stroke on a steel anvil). It also has a high ignition
temperature and is much more insensitive to static discharges than black
powder. At last it is relative non-poisonous.

2) It is sufficiently impressive

When properly made it has about the same performance as the KClO4/Al compo-
sitions. Crackers, maroons and air-shells make very loud reports, combined
with a beautiful bright white flash. It is very suitable as a powerfull
blowing charge for shells with nitrate-based (magnesium-)stars. Even from a
simpel cylindrical cardboard-shell the stars are spread almost ball-shaped.

About the ingredients:

KNO3

Must be dry and fine powdered. Fertilizer grade is ok, but it need to be
chloride-free (which it normally is).

Al-dust

"German dark pyro powder" gives the best result, but it also works excellent
with the fat-coated variants of paint-grade "silvery" Al-powder. These also
gives the composition a moisture protecting coating and improve its storage
stability.

The author of the rec.pyrotechnics FAQ claims that inhaled Al-dust destroy
the lungs. I find it hard to believe since it was used for many years in
inhaled form to relieve the breathing-pains on asthma-patients, and even
today Al-dust is sprayed out in the air in mines in the U.S. and Canada
because it bind dangerous silicate dust. But, on the other hand, Al is now
suspected to cause preageing (Alzheimers disease) if too much of it goes
into the blood, so don't eat it :-).

He also claims that fine Al-powder is pyrophoric and should be avoided.
This is also correct to some extent, but Al tend to protect itself with a
airtight coat of oxide, and normal grades of Al-dust and bronze is in its
production allowed to react with air in a controlled way to stabilize it.
These grades are definitely not pyrophoric. But, like other flammable dust
it is explosive when mixed with air in the right proportions.

Making and using flashpowder:

When making flashpowder, I use to ballmill the KNO3 and the S together,
and AFTERWARDS mix in the right amount of Al-dust on a sheet of paper.
(Always be carefull when using a ballmill to mix flammeable compositions).

Nitrate-based flashpowder demands more confinement than the KClO4/Al types,
but works well in ordinary cardboard tubes with glued endplugs. I sometimes
use reinforced PVC-hose (the kind used to water the garden) to make canon-
crackers (maroons). Cut it in 4"-10" pieces, tie up one end and fix with
tape. Fill up 1/3 to 1/2 with flashpowder, put in a fuse and then close the
other end. Very impressive! - But don't stand too close! - There is always
a risk of being hit by pieces of the tube or small stones from the ground.

Last but not least: Doing some or all of this may be illegal without a
special permission or license in your part of the Galaxy. Also, do show
common sense! - it does not help much to use a safe-to-mix formula if you
use the finished cracker to blow away your hand..  8-(

Peter A.


sender:
-- 
Peter Jacobsen, <pjac@ruc.dk>
-----------------------------