Why do we always use German Dark Aluminum?

[bblaze]

All good pyrotechnicists know to use German Dark Aluminum in high quality pyrotechnic reactions where Al is involved...

But, my question is what makes German Dark Aluminum dark in the forst place and also, why is it used more extensively and is recommended for use in pyrotechnics above your "generic" white powdered Aluminum?

[bblaze]

All good pyrotechnicists know to use German Dark Aluminum in high quality pyrotechnic reactions where Al is involved...

But, my question is what makes German Dark Aluminum dark in the forst place and also, why is it used more extensively and is recommended for use in pyrotechnics above your "generic" white powdered Aluminum?

[tmp]

IIRC, German Dark is made by glueing thin sheets of paper to the foil and
after drying the foil is stamped repeatedly causing the foil to break up into
smaller pieces. These pieces are then charred in an inert atmosphere at
high temperature. What remains probably needs some ball milling. The
powder is very reactive due to the higher surface area of the flakes rather
than what would be provided by spherical powder. There has been
speculation that the presence of the carbon formed during the charring
process and maybe some aluminum carbide lower the ignition point of
the powder.

The German Dark powder I keep for comparing to my homemade powder
will burn if ignited by a butane lighter. The same can be said for my own
homemade powder.

[tmp]

IIRC, German Dark is made by glueing thin sheets of paper to the foil and
after drying the foil is stamped repeatedly causing the foil to break up into
smaller pieces. These pieces are then charred in an inert atmosphere at
high temperature. What remains probably needs some ball milling. The
powder is very reactive due to the higher surface area of the flakes rather
than what would be provided by spherical powder. There has been
speculation that the presence of the carbon formed during the charring
process and maybe some aluminum carbide lower the ignition point of
the powder.

The German Dark powder I keep for comparing to my homemade powder
will burn if ignited by a butane lighter. The same can be said for my own
homemade powder.

[FUTI]

I never made any pyro device. So I have a question. Since those reactions are between solid reactants, it seems logical that contact surface determines reaction rate to some point. Also very small particles of metal like silver can look dark due to large light disipation/dispersion (whatever). So is the particle size of "German Dark Aluminum" reason for higher usage (since it gives better results due to higher contact surface) or its dark apperance isn't linked to particle size?

[FUTI]

I never made any pyro device. So I have a question. Since those reactions are between solid reactants, it seems logical that contact surface determines reaction rate to some point. Also very small particles of metal like silver can look dark due to large light disipation/dispersion (whatever). So is the particle size of "German Dark Aluminum" reason for higher usage (since it gives better results due to higher contact surface) or its dark apperance isn't linked to particle size?

[K9]

That would be the purpose of the 3 micron powder but I believe there are other powders of the size but aren't "German Dark". As far as the colour, I remember once seeing a picture of something like 1000 mesh powder that looked extremely dark for that reason.

[K9]

That would be the purpose of the 3 micron powder but I believe there are other powders of the size but aren't "German Dark". As far as the colour, I remember once seeing a picture of something like 1000 mesh powder that looked extremely dark for that reason.

[Jacks Complete]

Pitting in the surface, which would trap the light and increase absorption, could also be the reason. Think of a bolometer.

This pitting would also vastly increase the surface area. Additives would be likely to sit inside them, too, reducing the effects of water, and increasing the reactivity, as well as reducing the odds of settling out.

[Jacks Complete]

Pitting in the surface, which would trap the light and increase absorption, could also be the reason. Think of a bolometer.

This pitting would also vastly increase the surface area. Additives would be likely to sit inside them, too, reducing the effects of water, and increasing the reactivity, as well as reducing the odds of settling out.

[tmp]

Even my homemade powder is dark. The smaller the particle size, the
darker the powder appears. I have 650 mesh zinc powder that looks
almost like blackpowder.

[tmp]

Even my homemade powder is dark. The smaller the particle size, the
darker the powder appears. I have 650 mesh zinc powder that looks
almost like blackpowder.

[Jacks Complete]

Zinc oxidises very quickly, so it is mostly going to be zinc oxide, which is quite dark. It will get darker the longer you leave it.

[Jacks Complete]

Zinc oxidises very quickly, so it is mostly going to be zinc oxide, which is quite dark. It will get darker the longer you leave it.

[a_bab]

Generally speaking, almost all the mettals, once in the powdered form, will have a dark color. Al is known to preserve the silvery colour pretty very well.

The german dark Al color is because they add graphite, and possible because of the carbon left after charring the foil.

[a_bab]

Generally speaking, almost all the mettals, once in the powdered form, will have a dark color. Al is known to preserve the silvery colour pretty very well.

The german dark Al color is because they add graphite, and possible because of the carbon left after charring the foil.

[tmp]

My Zn powder is in an airtight container and has never changed color.
Maybe I'm just lucky.

[tmp]

My Zn powder is in an airtight container and has never changed color.
Maybe I'm just lucky.

[FUTI]

I believe that ZnO is white when pure although it has some off blueish tone. I think you mean that when surface of zinc is oxidised it darkens due to formation of smaller oxide particles on its surface that disperse light more then metal particles can.

3 micron powder is just above the range of particles that can make Tindal effect IIRC (approx. n*100nm is the best region)....maybe a guide for home brewer of aluminium powder? A guide in a way to try to make particle size as narrow as posible.

[FUTI]

I believe that ZnO is white when pure although it has some off blueish tone. I think you mean that when surface of zinc is oxidised it darkens due to formation of smaller oxide particles on its surface that disperse light more then metal particles can.

3 micron powder is just above the range of particles that can make Tindal effect IIRC (approx. n*100nm is the best region)....maybe a guide for home brewer of aluminium powder? A guide in a way to try to make particle size as narrow as posible.

[Jacks Complete]

Futi, you are correct, iirc. It does go white once it gets thicker - unless that is the hydroxide? I know moisture will turn it white faster than air alone, anyway. Chem. lessons were just too long ago...

tmp, it won't be shiny like when you cut it, though. It will have already oxidised, so it can't do more without more oxygen. Your airtight container stops this from happening.

[Jacks Complete]

Futi, you are correct, iirc. It does go white once it gets thicker - unless that is the hydroxide? I know moisture will turn it white faster than air alone, anyway. Chem. lessons were just too long ago...

tmp, it won't be shiny like when you cut it, though. It will have already oxidised, so it can't do more without more oxygen. Your airtight container stops this from happening.

[al93535]

I just wanted to let everyone know about pyroaluminum.com. I secured a sample from this guy and from the tests I have performed I would say this star-molecule 2-micron aluminum powder is better then german dark. Specifically german dark by eckart 5413 super-H flash grade aluminum. It seems to be more reactive, and packs more of a punch then the german powder. At two pound for 38 bucks, and no limits this is all I will be using from now on!

[al93535]

I just wanted to let everyone know about pyroaluminum.com. I secured a sample from this guy and from the tests I have performed I would say this star-molecule 2-micron aluminum powder is better then german dark. Specifically german dark by eckart 5413 super-H flash grade aluminum. It seems to be more reactive, and packs more of a punch then the german powder. At two pound for 38 bucks, and no limits this is all I will be using from now on!

[Macgyver]

I tried a flash consisting of 66.7% KClO4, 8.3% SbS3 and 25% Mg, and that was even louder than German black.

A teaspoon in a paper cup, no other confintment results in a loud explosion......

[Bert]

Flash made with Mg rather than Al will have a much lower "critical mass" (ammount needed for an audible report with no confinement) for a given particle size. The down side is that it doesn't store well- Mg will slowly oxidize away in contact with air or the common pyrotechnic oxidizers. Occasionaly it will QUICKLY oxidize away...

[azeotrope22]

The "Bright Flake" aluminum is processed with stearic acid, coating it to prevent a thin layer of oxide from forming. Its this same thin layer of oxide that protects aluminum from nitric acid. The "Dark Flake" has no coating.

[Luker]

I just wanted to let everyone know about pyroaluminum.com... At two pound for 38 bucks, and no limits this is all I will be using from now on!

Pyroaluminum.com does have very nice aluminum. But I wouldn't call it no limits. Because they say on the front page. 2 pounds per 24 hours for non-licensed individuals. Which would seam like a hassle if you wanted any more than two pounds. And with the how useful Al powder is I could see it disappearing rather quickly. But this company also seams to be able to make a lot more for licensed practitioners. The advertize "1/2 ton or more" for larger companies. Unfortunatley they don't show very many pictures of this 2 micron aluminum. Only in barrels. It would be interesting to see how dark it gets.

[Dexfurax]

Luker 99.9% of places in the USA will give you a pound every 6 months or 2 a

year... this is a great site and I'm starting to use!!

[nbk2000]

There used to be a site that sold bulk magnesium super-cheap. Less than $5 per pound in bulk.

They had ingot, block, turnings, and powder.

The link is/was on the Forum, but unable to find it. :(

The URL was something like magnesiumsales.net, or something similiar.

Anyone remember it?

[tmp]

NBK, that link is http://www.magnesiumsales.com located in Washington State IIRC.
I can't get to their website at the moment. I bought some magnesium from them.
It comes in brick-sized ingots on the larger orders. I hope they're still in business
because IIRC, I paid a little over $5 a pound on a 25 pound order. I've had a lot
of fun with that stuff ! :D

[al93535]

Pyroaluminum.com does have very nice aluminum. But I wouldn't call it no limits. Because they say on the front page. 2 pounds per 24 hours for non-licensed individuals. It would be interesting to see how dark it gets.

I have talked to this guy personally, and he will sell you any amount you want.

Here is a comparison picture. On the right is german dark 5413 super H, and the left is pyroaluminum.com 2 micron aluminum.

http://img.photobucket.com/albums/v242/al93535/darkal1.jpg

It looks lighter in the picture because it is a small amount, under a flash, and on white paper. It does indeed look darker in person, but you can compare the two side by side under identical lighting and background.

[Kingtaling]

I've got a few lbs of several kinds of Al to test over the next few weeks.
I've got 1lb of German dark from skylighter
I got 2 Lbs of 650mesh "blue" from ebay (supposedly not that great, atomized)
I got 2 Lbs of the 1250 mesh from ebay (same as above, also atomized)
I got 3 Lbs of Al from "exchem" or "expedited chemical" hes also on ebay
I got 2 Lbs from pyroaluminum.com to try
Ok thats it-
I have 2 kinds of KClO4 to try too, 5lbs from skylighter and 3Lbs from exchem.

Im new to this hobby and the only combo I've tried so far was last night: is both of exchem's stuff, their Al and KClO4 and it was the most amazing thing I've heard, it gave me an adrenaline rush and scared the crap out of me and I didnt have the guts to light any more off last night. It was only 2g in a small home-made salute from kraft paper. I thought for sure I was going to be caught!

[tmp]

The source of the KClO4 shouldn't make a difference as long as it's ground up
fine enough. My home-made(electrolysis) KClO4 does just fine in flash. The
amount of flash you fired is less than used in an M-80. M-80s use 45 grains,
or about 2.9 grams, of flash. Congratulations on test but be extremely
careful in all respects !

[Cobalt.45]

Exchem: $25/lb. delivered. They claim that the dark color is due to the small sized flakes (9u in their case) reflect light at such angles that the light is largely absorbed by the Al.

Their Al, as well as Eckart 5413 is treated with stearic acid, I'm told. The Al on Exchem site claims to be <80% Al, while 5413 is said to be on the order of 90%, but I wouldn't know how to verify this as fact.

I'm currently using German Blackhead from another ebayer, cyclocross1, as well as his KCLO4. Well pleased with both.

I'm using a rather different formula for flash: 5 parts KCLO4, 5 parts Bullseye, and 1 part of the aforementioned German Blackhead. It rocks. If someone else has any Bullseye, give this a try. You can go with 2 parts Al, and as little as 3 parts of Bullseye. Loudest is 5/5/2.

[krackerjack9]

Anyone know the status on PyroAluminum?? Their site has been down for over a week now.

[al93535]

They are out of business. The CPSC has pressured them so much they have called it quits. It was a good price while it lasted. I hope you guys bought a few lbs from them.

[Cobalt.45]

As soon as one site goes down, another pops up. The web sites vary from day to day, but as many as a half dozen different vendors of dark Al can be found.

Shame, though, that the powers that be hassle vendors to the point of shutting down. Something wrong with that.

Long as 1000 mesh or finer is available, making flash comps shouldn't be a problem. Other than ease of ignition, the so- called "Blackhead" Al isn't really necessary, if one knows what to do to make 14u "hot"...

[tmp]

The CPSC pressured them ...
As you said, when one goes down another pops up. I just make my own
Al and Mg powders, so FUCK the CPSC ! The assholes must have run out
of baby toys and lawn darts to ban.

[Bert]

How do you powder Mg?

[tmp]

Start with careful bench grinding as my Mg is in ingots. Ball mill and then
screen through 635 mesh. Treat with potassium dischromate to inhibit
oxidation. I've noticed that powdered Mg doesn't have to be nearly as
fine as powdered Al to be very reactive. Even the coarse powder off the
bench grinder is quite flammable. I bought the large ingots from
www.magnesiumsales.com although I'm sure they're out of business now.
A hell of a lot cheaper than those overpriced firestarter kits from Walmart.
Before I had the 635 mesh(stainless steel, VERY EXPENSIVE) screen I used
a very fine rayon fabric from an arts & crafts shop. I've yet to put it
through the finer fiiltering(HEPA) procedure like I do with powdered Al.

[Bert]

OK, thanks for the information. Before commercial processes for producing spheroidal powders by spraying molten Mg into inert atmospheres were developed, Mg was ground mechanically much as you describe. Have you ever tried using a coarse wire wheel rather than a grinding wheel? This is reputed to be more effective and less contaminating of the powdered metal.

50:50 Mg/Al alloy has the wonderful quality of being so brittle it ball mills more quickly than either Mg or Al- And the alloy's melting temperature is considerably below the ignition temp so it can be smelted and cast without inert atmosphere, given sufficient care. Be aware, if you try milling this at home that it's possible to mill it to the point where it will exhibit pyrophoricity... Not a good thing to dump out of the mill jar in your amateur pyro shop.

[tmp]

Bert, thanks for the tip on the wire wheel. That damn stone wheel, or
whatever it's made of, tends to clog fast and I have to use a stiff wire
brush to get some of the Mg out. I use the coarse wheel because the
fine wheel clogs even faster. There are 2 things that make the process
somewhat slow and a little bit messy. In the shed I keep a gargage bag
around the grinder because some of the Mg bits fly all over the damn
place. The plastic shield on the grinder and goggles keeps the shit out
of my eyes. Also, I can't put too much pressure on the ingot against the
wheel. The last thing I want is a fire so it's a nice slow grind. You're
right about its performance in flash. It's louder and brighter !

P.S. I'm trying to find another way to cut this stuff up faster. I have
over 20 LBS - most as large brick-like ingots. The price wasn't too bad
though. IIRC, it was $118.50 for 25 LBS - that's with the shipping !

[GTOzoom]

Ok, I know that german dark is made with graphite and that supposedly makes it better, but people are also saying that it is the super high surface area. Why would the graphite speed up the reaction? Carbon is less reactive than aluminum so what makes it so special? I'm not neccesarily doubting people but I just don't understand how the graphite would improve the Al.

I have 2 micron India Black Al. From what I understand this is simply superfine spherical Al powder ball milled into a flake form.(similar to German dark) Since the typical german dark is about 3-5 micron then I'm assuming that my India Black would have a slightly higher surface area than a typical german dark. So I'm going to buy some german dark from firefox once I get paid this month. I also think I'm going to get some German Black(What's the difference between german dark/black besides the particle size? Is there any?)

Once the stuff comes in I will run some tests to see if its the graphite or simply the surface area. I figure that the german dark that firefox sells is 2 micron(the same as my india) so if the same sized salute is used and one is louder than the other, than that will tell us if it is the graphite or not, right?

[tmp]

A Google search on MSDS sheets revealed the following autoignition data:

Aluminum powder - 760C
Carbon powder - above 350C
Graphite Powder - 730C

If graphite is being used in German Dark Al production, it could be to
inhibit oxidation, keep the powder from clumping, lower the igniton point,
increase flame propagation throughout the mixture, or any combination
of the four. The carbon from the charring process could exhibit similar
properties with an even lower ignition point. This is just speculation on
my part from existing data but what the hell it seems to work !

[Cobalt.45]

If graphite is being used in "German dark flake" Al, it wouldn't be because of its pyro properties, but rather as stated above, to help it pour more smoothly.

The percentage of C would not be high enough to alter the burn characteristics to any real degree, IMHO. Otherwise, graphite would be an ingredient of flash powder.

IIRC, S is used to enhance the burn rate, where applicable.

The difference between 2 and 4 micron flake AL is probably academic. Both/ either will get the job done, if flash comps are your goal.

Where you'll see a major difference is between Al and Al/Mg (magnalium) alloy.

[bluetuniclink]

Even my homemade powder is dark. The smaller the particle size, the darker the powder appears.

On another thread here (sorry, couldn't find it) someone announced finding a new Al powder that is so fine it does not refract light. That could make some impressive flash powder or thermite. They were looking into getting a sample to experiment with. If anyone can link to the thread it would be appreciated.

[Shalashaska]

Problem is you'd have to have an oxidizer with equal particle size to be REALLY impressive. Or if it's porous, the Al could just get stuck into the pores, as with black powder. Of course, I wouldn't want to be the one using a mortar and pestle on it XD

[Bert]

Problem is you'd have to have an oxidizer with equal particle size to be REALLY impressive. Or if it's porous, the Al could just get stuck into the pores, as with black powder. Of course, I wouldn't want to be the one using a mortar and pestle on it XD

Here is a quote from a rather knowledgable person wich may help explain the choice of Al and oxidizer particle xsizes and shapes for high performance flash powder. The information was initialy posted elsewhere in regards to the use of fumed silica in flash powders, but the discusion of oxidizer and Al particle size, type and distribution in the finished mix is relevant to this thread.

Hi all, in my experience with perchlorate based aluminium
flash powders, the fumed silicas are best. I prefer grade
EH-5 Cab-O-Sil. However, because the bulking agent has an
important physical role, it seems incorrect to call these
bulking agents extenders, fillers or diluents, etc...

The number of ideas on the actual role of a bulking agent
in flash mixtures gives me an opportunity to comment on a
little known rational in their use; especially as in some
of the high-performance military/aerospace flash mixes...

The physical chemistry function is to reduce bulk density
by increasing the separation distance between clusters of
fuel and oxidiser. Fumed silica does this by promoting an
equalisation of electrical charge. Ideally, the particles
of fuel are uniformly mixed among oxidiser particles, but
to get this to happen evenly, and safely, there must be a
specific particle size ratio between them, with a minimum
electrostatic charge to promote agglomeration; using what
is in essence a charged humidifier. Following this, flake
aluminium (fine bright waxed) is used as a cluster coater
leading to groups of aluminium coated clusters. To act as
a charge disperser (as thus a bulking agent) fumed silica
is finally added with light tumbling to separate clusters
and decrease the bulk density; it also neutralises charge
to minimise the electrostatic hazard: that's how it works
as a bulking agent...

Specifically, approximately uniform clusters of potassium
perchlorate with an atomised spheroidal aluminium receive
a monolayer of a suitable flake aluminium. Flakes work as
the coating where atomised spheroidal particles work best
as interstitial fuel; filling the spaces between oxidiser
particles. The particle sizes lead to near stoichiometric
ratio between the oxidiser and interstitial fuel. To make
the 'charged' clusters separate (remember that the waxing
on the flakes acts as a dielectric) fumed silica is added
to act as an intermediary charge disperser. The separated
clusters then leave the fumed silica between them causing
the mixture to bulk, which thus increases fire passage. A
greatly magnified ideal flash mixture may look similar to
the following illustration; of course, a mixture can only
approach the ideal with the correct selection of particle
sizes, shapes and the proper mixing techniques; like when
clusters are coated with flake they are 'warm' tumbled to
promote the waxed aluminium's cohesion, which leads to an
improvement in the robustness of the clusters - it's also
part of a critical post-humidification safe drying regime
before adding the charge neutralising fumed silica...

*. O* .* OA *O. * A.A*.O * AOA * AA.* *A* *AOA.
.AAAAAAA . * AAAAAAA * A AAAAAAAP * A..AAAAAAAO *
A.O.O.O.A A AO.O.O.OA .O A.O.O.O.A O * AO.O.O.OA
AO.O.O.OAO * A.O.O.O.A * OAO.O.O.OA.A A.O.O.O.AO *
A.O.O.O.A .AO.O.O.OA A A.O.O.O.A A* AO.O.O.OA
AO.O.O.OA * A.O.O.O.A . . OAAAAAAAO O A.O.O.O.A *
A.O.O.O.A A AAAAAAA *.O.* * AO*. OAAAAAAA.
.AAAAAAAO.O * .O. * AO.O.A O . * .A. * O
. * . * * * AAA .O. * A AAAAAAA. * *
*.*AAAAAO A* AAA O.AO.OA AAAAAAA * AO.O.O.OA O.*A
AO.O.OA AO.OA A.O.A AO.O.O.OA * AAAAAAAA *.O *
* A.O.O.A * A.O.A AO.OA A.O.O.O.A O.* AO.O.O.A *A
. AO.O.OA * AO.OA AAA AO.O.O.OA OA.AA.O.O.OA AO.
* AAAAA .O. A.O.A.O * .O A.O.O.O.A * AO.O.O.A. *
A.O* A * * AAA * AAAO AAAAAAA * A * AAAAAA O*.O
*AO. * .OO. * * AOAO O* . A* O .* .*. A

Where the coating aluminium flakes (A) surround the small
clusters: the oxidiser particles (O) and the much smaller
particles of interstitial spheroidal aluminium (.) with a
size chosen to fit neatly between the oxidiser particle's
spaces to produce a dense humidified structure. The fumed
silica (*), is added last to the 'structured' mix - being
dispersed between the clusters of bi-modal aluminium with
oxidiser - which causes the clusters to separate. This is
the way such a well-designed flash mixture appears with a
stereo microscope. This illustrates the roles of particle
sizes and shapes and the sequence and method of mixing to
obtain optimum structures. Indeed, the use of humidifiers
with some special blending techniques allow very specific
compositional structures to be engineered, not just flash
powders...

Given that flake aluminium coats an almost stoichiometric
mixture of spheroidal aluminium and oxidiser, most excess
aluminium of the flash is the flake aluminium. A lot more
can be written on this subject, although the above should
be sufficient to allow others to comment...

Regards,