18 replies to this topic

[E-tech]

Found a video for the production of German Dark. I remember reading somewhere that this material now has limits on how much can be purchased in a year- true?
Has anyone tried this method the video is showing?
worth it?
What exactly is it about German Dark that makes it so special?
Sorry for the inexperience- pyrotechnic uses for powdered Al are new to me. I have some catching up to do.

http://www.metacafe....luminum_powder/

[wjames]

this sounds very dangerous to me............very dangerous indeed - and im sure others will agree....

"powdered" Al.....in a blender.....Thats just plain crazy. Al creates an explosive atmosphere when airbourne.......

[cooperman435]

Thats not german dark ali lol. It may look like it because its dark and contains ali but I assure you its not! Where do these people get the idea they know what there talking about lol

[pyromaniac303]

The particle size and shape will be totally different to german dark... It will be basically the same aluminium you put in, just oxidised outer surface and with paper impurities!

German dark aluminium contains a small percentage of carbon as an opacifier which helps it absorb more infrared heat energy and burn at a faster rate than a similar bright flake aluminium of exactly the same particle size.

There may well be purchasing quantity restrictions in the US from certain suppliers, read up on the CPSC court case against firefox for more information on this though. I'm sure buying a large amount in any country is going to attract a bit of unwanted attention though, there are safer ways to create a report effect than using flash.

Also blending/coffee grinding is a perfectly legitimate way of powdering most fuels, but a blender is best for reducing relatively large particles down to medium sized, then use a ball mill to get the really fine stuff. I can't honestly see a blender ever producing 3 micron flake aluminium, even after several hours of use. As wjames says though, be careful, fine dust/air mixes can cause explosions so try to allow enough time for dust to settle before opening the jar afterwards.

If you insist on making your own metal powders then read up on all the safety information assosciated with it, as there have been cases where metals have spontaneously ignited when the mill jar is opened.

[paul]

Yeah, they go pyrophoric when too fine... There was a rec.pyro thread on someone who opened a milling jar filled with ultra fine (after milling, of course) mg powder. It ignited, you can guess the rest...

Best to do it in some inert atmosphere like filling the jar with some really "heavy" gas and air-tighten it... Or remote-opening
it.

@ video: First: LOL Second: There were rumors on the production of German Dark Al... I read somewhere it is produced
like that:

Al-coated paper (like that stuff around gums) is burnt. You get a fine Al-stuff then. This is milled then to archive the typically DARK (carbon-residues)
colour!

[E-tech]

interesting- I wondered if just a physical mix of burnt paper and Al could be the "secret" of German dark. - Guess not.
Would the burning of a gum-wrapper type of paper-backed foil actually work? (might actually be inexpensive if you could find the correct type of gift-wrapping paper)
Would it need to be done in a sealed container to exclude air?
is the Indian blackhead Al the same as the German dark?

Thanks for the info so far- I'm learning!

Edited by E-tech, 23 November 2008 - 09:41 AM.

[knackers]

the reason why newspaper is mentioned is because german/indian dark Al contains lamp black ( hydrocarbons) but i highly doubt there will be enough on the paper as print, , i would also think it would have to be milled in a metal tub with perhaps metal grinding media such as stainless steel in an inert atmosphere to be able to be milled fine enough

added..... i have also read ( not tried ) butcher paper, with a very thin plastic film on one side, is used as when charcoaled also leaves a hydrocarbon residue coating
which is a prime ingredient

so my 2 bobs worth is...... i understand it is made as follows, ( somebody correct me if i'm wrong ) starting with fine bright Al 300# plus, ( blended Al would sufice but the finer you start with the better)....in your retort with butcher paper for charcoal and hydrocarbon, cooked as per charcoal,, then is placed in the mill with lamp black, " milled in a sealed tub with either Argon, Co2 or eqivalent inert gas until milled ,

This is not a method to try ! it is my understanding of how its made, Do not try this as for one thing if your tub leaks atmosphere you are setting up for a catastrophe

Edited by phill 63, 23 November 2008 - 11:04 AM.

[knackers]

[quote name='paul' date='Nov 23 2008, 06:33 PM' post='52314']
Yeah, they go pyrophoric when too fine... There was a rec.pyro thread on someone who opened a milling jar filled with ultra fine (after milling, of course) mg powder. It ignited, you can guess the rest...)



Mg is different to Al, Mg will self combust ( go pyrophoric when moisterised)..... Hence volkswagon used to make Mg block motors, when hot and with water sprayed on them they would ignite,, thats why they were oil cooled, instead of water cooled,,

so therefore, when a milled ultra fine Mg containing tub was opened , the moisture in the air made it pyrophoric,

Al won't do this unless there is an external heat source,,


Added...... maybe thats why you can buy German/indian dark pyro Aluminium and not German/indian dark pyro Magnesium ....

Edited by phill 63, 24 November 2008 - 08:17 AM.

[spanner]

There was a rec.pyro thread on someone who opened a milling jar filled with ultra fine (after milling, of course) mg powder. It ignited, you can guess the rest...)

This happened a little differently than that. A brief description of events and the result of the accident can be seen here: http://www.bobforward.com/magmill.htm

Mg is different to Al, Mg will self combust ( go pyrophoric when moisterised)..... Hence volkswagon used to make Mg block motors, when hot and with water sprayed on them they would ignite,, thats why they were oil cooled, instead of water cooled,,

so therefore, when a milled ultra fine Mg containing tub was opened , the moisture in the air made it pyrophoric,

Al won't do this unless there is an external heat source,,


Added...... maybe thats why you can buy German/indian dark pyro Aluminium and not German/indian dark pyro Magnesium ....

Please do not think for a minute that aluminum won't go pyrophoric under the right (wrong?) circumstances- it will! And water or external heat is not necessary- only atmospheric oxygen. More: http://cameochemical.../chemical/14570

VW engines, unless molten, will not ignite if gotten wet. Else, every time it rained they would have been on fire! Magnesium will flare spectacularly if, while burning, water is sprayed on it, though. It'll even keep burning if sprayed with a CO2 fire extinguisher.

Edited by spanner, 24 November 2008 - 10:19 AM.

[knackers]

VW engines will not ignite if gotten wet. Every time it rained they would have been on fire! Magnesium will flare spectacularly if, while burning, water is sprayed on it, though.
[/quote]


i didn't mean at normal operating temp.... i meant a hot engine, ( 40 c summer day ) bonnet lifted and hosed down to cool it down,,,

i've held this belief for 30 odd years with no solid proof as far as i know they don't make Mg blocks any more and havn't done for over 20 years


added..... i know Mg powder ( and other powdered metals ) react differently than a more dense block. and i have just ignited an inch of Mg ribbon and dunked it in a bowl of cold water, and to my suppries.................it went out !

Edited by phill 63, 24 November 2008 - 10:40 AM.

[GZ22]

Here are some clips of water being applied to burning Mg engine components, and also a firefighter's page:

http://uk.youtube.co...h?v=KY9ri-UOoLo

http://uk.youtube.co...feature=related

http://midsouthrescue.org/id21.html

[Frozentech]

This happened a little differently than that. A brief description of events and the result of the accident can be seen here: http://www.bobforward.com/magmill.htm

There was also Lloyd Sponenburgh, who was using his mill without any media, to mix cabosil with Mg powder. His ignited and seriously burned him without even opening it.

[bigtonyicu]

guys take a look at he last few pages of the Fash powder pages, I've done lots of work and I have a full analysis on what's actually "German dark" and how it's Made...

[E-tech]

Thanks for the heads-up on that discussion thread, Bigtonyicu!
I notice that the presence of lampblack is a big factor in "true" German dark.
This would have to come from something other than a source of cellulose (i.e. paper). most likely, you say, a plasticized paper.
Wouldn't something like old newspaper produce something similar? What was German Dark originally made for? If it was made for the small world of pyrotechnicians- would it have been possible that a cheap source of paper (old newspapers) were used for it's manufacture?
What type of weight ratios would we have to start with in order to mimic the numbers shown by your lab work-up of 5413-H?

[bigtonyicu]

Thanks for the heads-up on that discussion thread, Bigtonyicu!
I notice that the presence of lampblack is a big factor in "true" German dark.
This would have to come from something other than a source of cellulose (i.e. paper). most likely, you say, a plasticized paper.
Wouldn't something like old newspaper produce something similar? What was German Dark originally made for? If it was made for the small world of pyrotechnicians- would it have been possible that a cheap source of paper (old newspapers) were used for it's manufacture?
What type of weight ratios would we have to start with in order to mimic the numbers shown by your lab work-up of 5413-H?

Lamp Black does not come from paper, if comes from the incomplet combustion of plastics, fat, or hydrocarbon (I'm sure there's other sources); Old news paper won't produce lamp black even when degassed in a retort is will only make charcoal.

Eckart is a pigment manufacturer so I'm guessing it's initial use was either pigments or pyro there's not that many use for a powder that fine.

As for the ratio, that depends on the paper (mostly the thickness of coating on the paper). But with out a stamp mill of a hammer mill you wont be able to acheive the 1-5 micron sizes needed.