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Author: Subject: Flash powder detonation
crazedguy
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[*] posted on 15-12-2010 at 16:55


Quote: Originally posted by quicksilver  


Edit:

If you want color - you generally need some chlorine. On occasion some of a lightest amount of parlon will yield some of the most brilliant coloration.
However the peroxides (as used in tracer composition) will get some fantastic color.

[Edited on 15-12-2010 by quicksilver]

Could you give more info on this or a source? For a while now I have been looking for a way to color my flash compositions, but as color I don't mean the burning I mean like the color of an M80 going off. Just haven't been able to find something that actually worked for that.




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[*] posted on 15-12-2010 at 17:24


Quote: Originally posted by quicksilver  
Edit:

If you want color - you generally need some chlorine. On occasion some of a lightest amount of parlon will yield some of the most brilliant coloration.
However the peroxides (as used in tracer composition) will get some fantastic color.


Perchlorates and chlorates already have chlorine. If you mix the barium and strontium ones with some organic chemicals (hexamine-sugar-chromate mixtures or nitrated cellulose powder, for example) instead of metals, you get rich colors, but the burning rate is slower than flash powders (except in the case of guncotton soaked in solutions of these salts and then carefully dried; that gives a fast colored flash.)
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[*] posted on 15-12-2010 at 23:13


If you're trying to make colors, why use aluminum? The purest colored flash powders are all made with magnesium for a reason. The aluminum oxide formed is a fairly decent white light emitter, which will wash out or over power any colorant that may be formed. You can get around this by a relative excess of chlorine to form aluminum chlorides, which are far more flame transparent. Magnesium oxide doesn't obscure visible colors nearly as much. I'm told it emits more in the UV, but I haven't looked at a spectra recently to check that out.

Some extra chlorine in the flame will ensure a greater concentration of the BaCl emitting species, which is the one you want. Otherwise you get some BaOH, amongst other things, which is more of a yellow-green to lime green color. Sulfur can help to generate free chlorine in a flame, but the chlorine is already where you want it when starting with barium perchlorate. If it behaves anything like barium chlorate, I'm not surprised it's underwhelming. For having the reputation of instability, it can be a somewhat sluggish oxidizer.
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[*] posted on 16-12-2010 at 07:16


Quote: Originally posted by Mumbles  

Some extra chlorine in the flame will ensure a greater concentration of the BaCl emitting species, which is the one you want. Otherwise you get some BaOH, amongst other things, which is more of a yellow-green to lime green color. Sulfur can help to generate free chlorine in a flame, but the chlorine is already where you want it when starting with barium perchlorate. If it behaves anything like barium chlorate, I'm not surprised it's underwhelming. For having the reputation of instability, it can be a somewhat sluggish oxidizer.


I also agree he overwhelmed it with Al or expected results that demanded a serious excessive chlorine source. Some colors are tough anyway (as a "flash").
I think a guy will read so much about rich coloration of stars, etc and then have a concern that a flash should make at least something close......I think it's a natural assumption.

There was some studies of how the eye can become overwhelmed in perception with high intensity light & that may play a very big part in many experiments with color. Additionally, it's often daylight when the experiment is conducted; complicating it further with background and a pupil already constricted.



[Edited on 16-12-2010 by quicksilver]




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[*] posted on 16-12-2010 at 17:12


Quote: Originally posted by Mumbles  
If you're trying to make colors, why use aluminum? The purest colored flash powders are all made with magnesium for a reason. The aluminum oxide formed is a fairly decent white light emitter, which will wash out or over power any colorant that may be formed. You can get around this by a relative excess of chlorine to form aluminum chlorides, which are far more flame transparent. Magnesium oxide doesn't obscure visible colors nearly as much. I'm told it emits more in the UV, but I haven't looked at a spectra recently to check that out.

Some extra chlorine in the flame will ensure a greater concentration of the BaCl emitting species, which is the one you want. Otherwise you get some BaOH, amongst other things, which is more of a yellow-green to lime green color. Sulfur can help to generate free chlorine in a flame, but the chlorine is already where you want it when starting with barium perchlorate. If it behaves anything like barium chlorate, I'm not surprised it's underwhelming. For having the reputation of instability, it can be a somewhat sluggish oxidizer.


If you read older sources, like Davis, you will see that aluminum flash powders containing barium salts are reported as supposedly making a "green flash". Even nowadays you can still find aluminum flash powders that supposedly give such a green flash:

http://www.privatedata.com/byb/pyro/pfp/flash.html

Having tested several of these, it seems to me that the word "green" here is very relative. It's a very pale greenish tinge, actually, not what you initially expect if you have seen things that fit the definition of a "green flash" much better (like guncotton soaked in a barium perchlorate solution, then wringed out and dried.)

Tinkering with magnesium powder has a couple of problems:

1- It is not as easy to find as aluminum powders

2- It is reportedly more dangerous than aluminum
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[*] posted on 16-12-2010 at 20:42


Magnesium is much more expensive so I never really planed to use it, I will just keep it simple with my regular flash. Which brings me to my next point we should have a video section.



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[*] posted on 16-12-2010 at 23:51


I suppose I am a bit spoiled with my access to magnesium, so I always over assume it's ease of acquirement.

Unless you're using bright paint grade aluminums, it should be about as easy to acquire magnalium, which should offer an improvement in color. If not, it's not too difficult to manufacture, which shouldn't be much of a problem considering many here's insistence on ball milling aluminum foil.

As far as the pfp database, I only see one reference to a colored flash with aluminum, one by Wouter Visser. You will notice that all of the rest are composed of magnesium. I don't know who published the color flash powder formulae first, but the earliest I really know of is Degn, from the 1960's. Electric stars were known much earlier, and some may very well function as colored salute formulas.

Probably the most well known examples of colored salute mixtures is in the maltese beraq shells. All of the formulas use magnesium. While, as you mentioned magnesium is typically more reactive than aluminum, it functions the best. Lord knows there is no shortage of aluminum powder on the island. Be honest, colored flash powders are a niche composition typically reserved for exhibition. If you look at exhibition formulas from Davis, Weingart, etc. you will notice a distinct preference for color/effect over cost and safety. The same typically is used for these formulas. Even so, colored flashes are normally much weaker than a typical standard flash powder, so special techniques and more reactive formulas are used. If magnesium flashes would require brass balls, for the colored beraq formula/construction would require a stainless steel set which has been tempered and oil hardened.

It seems a bit odd to me that you are using barium perchlorate, but magnesium is too difficult to acquire and cost prohibitive.

[Edited on 12-17-2010 by Mumbles]
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[*] posted on 17-12-2010 at 02:17


Quote: Originally posted by Mumbles  
I suppose I am a bit spoiled with my access to magnesium, so I always over assume it's ease of acquirement.

Unless you're using bright paint grade aluminums, it should be about as easy to acquire magnalium, which should offer an improvement in color. If not, it's not too difficult to manufacture, which shouldn't be much of a problem considering many here's insistence on ball milling aluminum foil.

As far as the pfp database, I only see one reference to a colored flash with aluminum, one by Wouter Visser. You will notice that all of the rest are composed of magnesium. I don't know who published the color flash powder formulae first, but the earliest I really know of is Degn, from the 1960's. Electric stars were known much earlier, and some may very well function as colored salute formulas.


Check Davis, chapter on Chinese firecracker manufacture, where he already mentions green flash aluminum compositions (as he states, he got the info on such compositions from Allen F. Clark, who was apparently a pyrotechnist from Massachusetts.)


Quote:
I suppose I am a bit spoiled with my access to magnesium, so I always over assume it's ease of acquirement....

It seems a bit odd to me that you are using barium perchlorate, but magnesium is too difficult to acquire and cost prohibitive.


It seems we have a reverse situation here: for me it is easy to make this barium salt, since I have access to both barium hydroxide and ammonium perchlorate.
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[*] posted on 18-12-2010 at 12:29


I have access to Aluminum and Magnesium its just that when Al is 6 dollars cheaper a pound, and I use pounds rather fast and Al produces the destructive power I am looking for Magnesium just never seemed like the powder for me.



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[*] posted on 18-12-2010 at 12:44


Quote: Originally posted by Blasty  


Check Davis, chapter on Chinese firecracker manufacture, where he already mentions green flash aluminum compositions (as he states, he got the info on such compositions from Allen F. Clark, who was apparently a pyrotechnist from Massachusetts.)




Allen F. Clark did not truly publish (TTBoMK) but may have been the fellow who made the original very old film of "Chinese Firecracker Making". It's great that you brought up his name as I did a fairly in-depth search on that fellow as some years back I was VERY interested in the "Thousand Hex-Brick" hand manufacturing technique; using two bamboo tools and scrap paper. I actually DO have some leads on this but I don't want to pull this whole thread off in that direction. *


The true Ekart 5413 is not sold as "pyro" aluminum but the "5413-process" IS. The true Ekart material is incredible. It is what is known as an "ink-grade" pigment. Imagine what lengths a company would go to maintain a 2um size; no more and no less to produce a pigment fit for ink!

Please see the actual Ekart link:

http://www.eckart.net/products/aluminium-pigments/powder/pro...

* There ARE copies of that film! Again: to the best of my knowledge it was made during the "silent-film era", lasting approx 10-minutes (or less) & was said to have some written pre-projection script or text that was lost.


The BEST literature I have read on the subject of color was the Pyrotechnic Literature Series (especially #6), that was "Studies in Flame Colored Compositions" (Takeo Shimizu Part 3) If you can EVER get that: BUY it or copy it. As it has some of the most in-depth and complete works Mr Shimizu had done and was the culmination of his lecture series.
The complete set is no longer available as it was a $400 printed (transcribed lecture series sold by PGI or FWN private printing). Each lecture was $35 back in the day. The most difficult to find is 2/2 Report & Flash Composition Experiments. Genuine collector's material (I think there is 12 in total).






[Edited on 18-12-2010 by quicksilver]




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[*] posted on 18-12-2010 at 16:59


Quote: Originally posted by quicksilver  
Allen F. Clark did not truly publish (TTBoMK) but may have been the fellow who made the original very old film of "Chinese Firecracker Making". It's great that you brought up his name as I did a fairly in-depth search on that fellow as some years back I was VERY interested in the "Thousand Hex-Brick" hand manufacturing technique; using two bamboo tools and scrap paper. I actually DO have some leads on this but I don't want to pull this whole thread off in that direction. *


* There ARE copies of that film! Again: to the best of my knowledge it was made during the "silent-film era", lasting approx 10-minutes (or less) & was said to have some written pre-projection script or text that was lost.


Sounds interesting. What were you able to find out about both the man and the film? Davis' references to him are all about pyrotechnics, that's why I assume he was a pyrotechnist that Davis was personally acquainted with. Davis also mentions some of his brothers, one of them apparently with probable connections to the National Fireworks Company.
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[*] posted on 19-12-2010 at 06:02


Please excuse this as being a bit OT but from what I found Clark was both an investor and involved with pyrotechnics in most every way a man could be before & during the 1920's. The company was one of his holdings I believe as was either the film or a series of materials that Clark wanted to make public. He was certainly a man who kept to his passion. I do not know if he had a scientific background per se' but he did document almost everything that he could re; pyrotechnics. Some mention of "War-time enterprises" made me think perhaps he was involved in WWI activities but in general, he was a great source to Davis & perhaps a personal friend.



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[*] posted on 20-12-2010 at 09:33


Quote: Originally posted by quicksilver  

The BEST literature I have read on the subject of color was the Pyrotechnic Literature Series (especially #6), that was "Studies in Flame Colored Compositions" (Takeo Shimizu Part 3) If you can EVER get that: BUY it or copy it. As it has some of the most in-depth and complete works Mr Shimizu had done and was the culmination of his lecture series.

The complete set is no longer available as it was a $400 printed (transcribed lecture series sold by PGI or FWN private printing). Each lecture was $35 back in the day. The most difficult to find is 2/2 Report & Flash Composition Experiments. Genuine collector's material (I think there is 12 in total).


---------
Can be had from the publisher Journal of Pyrotechncs

http://www.jpyro.com/litseries/Shimizu/shimizu3.htm

Can be previewed at Google.com/books

Free from DTIC.MIL

1.
View TR Citation | View Full Text pdf - 510 KB
Title: RELATIONSHIPS OBSERVED IN COLORED FLAMES
Personal Author: Douda, B E
Corporate Author: NAVAL AMMUNITION DEPOT CRANE IN
Source Code: 247250
Page Count: 18 page(s)
AD Number: AD0607490
Report Date: 25 SEP 1964
Distribution Code: 01 - APPROVED FOR PUBLIC RELEASE
Report Classification: U - Unclassified
Collection: Technical Reports
2.
View TR Citation | View Full Text pdf - 2 MB
Title: Theory of Colored Flame Production
Personal Author: Douda, B E
Corporate Author: NAVAL AMMUNITION DEPOT CRANE IN
Source Code: 247250
Page Count: 68 page(s)
AD Number: ADA951815
Report Date: 20 MAR 1964
Distribution Code: 01 - APPROVED FOR PUBLIC RELEASE
Report Classification: U - Unclassified
Collection: Technical Reports
3.
View TR Citation | View Full Text pdf - 1 MB
Title: COLORED FLARE INGREDIENT SYNTHESIS PROGRAM
Personal Author: Douda, B E
Corporate Author: NAVAL AMMUNITION DEPOT CRANE IN
Source Code: 247250
Page Count: 44 page(s)
AD Number: AD0447410
Report Date: 10 JUL 1964
Distribution Code: 01 - APPROVED FOR PUBLIC RELEASE
Report Classification: U - Unclassified
Collection: Technical Reports
4.
View TR Citation
Title: Emission Studies of Selected Pyrotechnic Flames,
Personal Author: Douda,B E
Corporate Author: NAVAL AMMUNITION DEPOT CRANE IN
Source Code: 247250
Page Count: 25 page(s)
AD Number: ADA951839
Report Date: 04 AUG 1964
Distribution Code: 01 - APPROVED FOR PUBLIC RELEASE
Report Classification: U - Unclassified
Collection: Technical Reports

And a SL of other stuff.
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[*] posted on 20-12-2010 at 14:03


Quote: Originally posted by crazedguy  
Quote: Originally posted by quicksilver  


If you want color - you generally need some chlorine. On occasion some of a lightest amount of parlon will yield some of the most brilliant coloration.
However the peroxides (as used in tracer composition) will get some fantastic color.

[Edited on 15-12-2010 by quicksilver]

Could you give more info on this or a source? For a while now I have been looking for a way to color my flash compositions, but as color I don't mean the burning I mean like the color of an M80 going off. Just haven't been able to find something that actually worked for that.



Sure —

The WiZard's Pyrotechnic Formulary
http://www.skylighter.com/ sells them. Though in my opinion
the price is a little high! Then he probably has sold more at his
higher price then I could at my lower price! Weird.

Extracted from la formulary. I have it in a DB (a DOS program!)
so I just extracted these.



SALUTE RED
DEGN LIPPY+PALDER
MAGNESIUM 50%
STRONTIUM/NITRATE 50

Salute green
Degn
Magnesium 10 pts
Barium/nitrate 10
PVC 1

SALUTE YELLOW
DEGN
MAGNESIUM 1 pts
SODIUM/OXALATE 1
POTASSIUM/PERCHLORATE 1

SALUTE VIOLET
DEGN
MAGNESIUM 10 pts
POTASSIUM/PERCHLORATE 10
CUPRIC/OXIDE 3
STRONTIUM/NITRATE 3
PVC 1

SALUTE BLUE
DEGN
MAGNESIUM 20 pts
POTASSIUM/PERCHLORATE 20
PARIS/GREEN 6
PVC 1

SALUTE WHITE
DEGN
MAGNESIUM 1 pt
POTASSIUM/PERCHLORATE 1

SALUTE VIOLET
DEGN PYROTECHNICA VI
STRONTIUM/NITRATE 8 pts
PVC 1
MAGNESIUM 16
PARIS/GREEN 8

Salute blue
Pyro-Tec
Potassium/chlorate 10 pts
Magnesium 13
Paris/green 7
PVC 1

Salute green
Pyro-Tec
Potassium/chlorate 3 pts
Magnesium 13
Barium/chlorate 10
PVC 2

The red works best, however, even then looking directly at it -
it is toooo bright. Reflected light looks the best.

None of these are safe. If they were safe they wouldn't work.
Keep the quantities mixed to a minimum or less.

MAJOR SOURCES FOR THE PYRO FORMULARY


AFN- American Fireworks News, Star Route Box 30, Dingmans Ferry PA 18328

ALLEN- An itinerant pyro Mr. Allen worked for a large number of companies, e.g., Rossi, Del Grande, Hitt, &c.. Everywhere he worked he collected formulae in his secret book. I have incorporated most of them in this compilation, eliminating those that were obviously wrong. There are, however, included a few that look possible, but not likely.

APFN- American Pyrotechnist Fireworks News Published October, 1970 to November, 1976.

BLESER RSS- David Bleser, Round Stars and Shells. Published by: American Fireworks News, Star Route Box 30, Dingmans Ferry, PA 18328.

CA- Chemical Abstracts vol##, ######

CHEMICAL FORMULARY- Chemical Publishing Co N.Y. Various Volumes. Vol. #1 1933.

CHEM LIT- A series of pamphlets on fireworks available from: Jim Saxon, 208 Franklin Blvd., Mahomet IL. 61853

CHEMPAC- A list of of formulae attributed to the now defunct Chempac Supply Co. They were probable copied from: James Cutbush's A System of Pyrotechny 1823.

BAECHLE Pch- Pyrocolor Harmony: A Designers Guide. Joel H. Baechle, 105 Erin Place, Jackson CA 95642.

DAVIS- Tenney L. Davis. The Chemistry of Powder and Explosives, 1943.

DENG- From a series of how-to's distributed by Westech 1970.
Chem

DICKS- Encyclopedia of Formulas & Processes 1872. In the PoorMan's James Bond.

ELLERN- Dr. Herbert Ellern. Military and Civilian Pyrotechnics, 1968.

ENCICLOPEDIA VNIVERSAL ILVSTRADA- 70 Vols. in Spanish, formulae from Vol. XLIV; Pirotechnia.

GREEN NOTES- Published by the now defunt Megatech Supplies, Myrtle Beach SC

HATCHERS NOTEBOOK- By Julian S. Hatcher. Stackpole Co. 1947. 3rd Ed. 1962.

HENLEY'S- Twentieth Century Book of Formulas, Processes and Trade Secrets. Publishers Agency Inc. 1937.

HI-LOW BOOM- Philip J. Danvisevich, 1966. Ken Hale Publications POB 395 McDonald OH 44437

KENTISH- Thomas Kentish, The Complete Art of Firework-Making 2nd Ed.

LANCASTER- Lancaster, Ronald, Takeo Shimizu, R.E.A. Butler, and R.G. Hall. Fireworks: Principles and Practice. 1972.

LIPPY AND PALDER- Modern Chemical Magic

MC- Fred L. McIntyre. A Compilation of Hazard and Test Data for Pryotechnic Compositions, 1980.

OP2793- NAVWEPS OP 2793 Toxic Hazards Associated with Pyrotechnic Items, 1963.

PGII BULL- Pyrotechnist Guild International Bulletin PGII Sec/tres Ed Vanasek, 18021 Baseline Avenue, Jordan, MN, 55352

PATR2700- The Encyclopedia of Explosives and Related Items. 10vols.

PYROTECHNICA- Pyrotechnica Publications, Robert G. Cardwell, 2302 Tower Drive; Austin, Texas 78703

RDTR 11- Experiments in Developing Green Flare Formulas.

RDTR 31- Investigation of Visibility and Formulation of Ashless Blue Flare.

RDTR 71- Spectral Analysis of Pyrotechnic HCl Emissions.

SHIMIZU- Takeo Shimizu, 1981. Fireworks: The Art, Science and Technique.

SHIMIZU 2- Takeo Shimizu, 1976. Fireworks: From a Physical Standpoint, Part II.

PYROTEKNIKDAGEN, Foredrqag vid. Swedish Pyrotechnic Conferences. Various years.

TECHNO-CHEM- Receipt Book of 1896. In the Poor Man's James Bond.

PSM- Book of Fourmulas: Recipes, Methods & Secret Processes. 1932.

TM1316- Survey of Sensitivity Characteristics of Typical Delay, Igniter, Flash, and Signal Type Pyrotech¬nic Compositions. 14pg. April 1964.

ULLMANN 4- Encyklopadie der technischen Chemie; 4th Edition.

USP- United States Patent #,###,###

WEINGART- George W. Weingart, Pyrotechnics, 1947.


As suggested comps used for tracer ammo will work. I can say from
experience that at least one will work!!! File them under HOT
SHIT
.


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[*] posted on 3-1-2011 at 06:08


Due to the usual New Year's fireworks mayhem around this area these past few days, I was able to further test these flash powder compositions with the fine atomized aluminum powder, this time confined in cardboard tubes, both home-made with Kraft paper + glue/paste and machine-made spiral tubes (such as used by pyrotechnists.) The tubes were about 2 to 2 1/2 inches long, with a bore of about 1/4 of an inch and a wall thickness of about 1/16. I employed the "can test" method to get an idea of the "striking" force of the mixtures. This basically consists in putting a measured charge of the composition inside such tubes, and then inserting it inside a metal can, such as a soda or juice can. But I don't mean the flimsy aluminum cans commonly used in the US for such products, but those still used for sodas and juices in some countries, specially in Latin America and Asia, like these coconut water cans that you can find in the international section of many supermarkets:

http://www.philamfood.com/images/P/0016229901479.jpg

These are actually made of steel sheet and it takes much more force to break through them (the flimsy American aluminum soda cans are easily ripped apart even by 1 gram charges of a good fast black powder.) For safety reasons, a hole is dug up in the ground and the can with the charged tube is placed in it before setting it off, just in case the explosion is too violent and throws any shrapnel around. Charges not exceeding one gram were used.

This was only a preliminary set of tests, which would need to be repeated more times, which I might do later on. The results can be summarized as follows:

In both the home-made and machine-made spiral tubes the nitrate and sulfate flash powders just blew the hot glue end plugs and did not burst the tubes. In this sense, they behave like black powder: they seem to need very strong confinement for such a thing to happen. This strong confinement was achieved in the same manner that I use for making black powder burst through such cardboard tubes without blowing the plugs: by drilling 4 opposing holes about 5mm from each end of the tube and injecting the hot glue through them. This gives a very strong seal.

The sulfate and nitrate mixtures did not function well in the home-made tubes. They tend to rip apart only one side of the tube (the "upper" side; the tubes are laying down horizontally inside the cans.) In this sense, these flash powders seemed again to behave like black powder confined in the same tubes. In the machine-made spiral tubes a bursting of all the tube was achieved. However, not even 1 gram of such mixtures were able to appreciably dent the steel sheet body of the cans. The lids of the cans were blown off or severely dented, but the strongest part of the can (its "body") was pretty much left intact. These flash powders still give a very loud report. 1 gram of the barium sulfate mixture gives a sharp and loud report, but, as already pointed out, it has to be strongly confined for it to perform at its best (the claim that this mixture "makes a nice noise in open tubes" does not seem to be true, at least not when using fine atomized aluminum.)

The mixtures containing perchlorates worked well even in the home-made tubes, and they did not need specially strong confinement, normal hot glue plugs worked just fine. The old firecracker mixture reported by Davis (which he got from Clark) of equal parts sulfur, aluminum, barium nitrate and potassium perchlorate seemed to be the strongest of the ones tested. 0.8 g of it not only blows the lids of the cans but gives a plainly noticeable dent to its body. Needless to say, it gives a sharp loud report.

The observation by Davis that the flash powders containing chlorates and perchlorates are "fulminating explosives when confined" (as opposed to those that do not contain them) seems thus to be accurate.

[Edited on 3-1-2011 by Blasty]
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[*] posted on 3-1-2011 at 07:34


Mixtures with alkali nitrates as oxidiser seem incapable of fulminating - according to Davis, black powder has never been known to do anything but burn!
But lightning is the root of the word "fulminate" and thunder the root of "detonate" . . .
Without the alien it's "donate"!


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[*] posted on 31-1-2011 at 21:17


Isuppose what I should have made clear when I originally posted this question is that I'm wondering if flash powder ever undergoes DDT. Does flash powder detonate when ignited by spark, spitting flame, fuse etc.,whether confined or in masses of sufficient quantity?

[Edited on 2-1-2011 by prometheus1970]




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[*] posted on 1-2-2011 at 09:03


70/30 flash has a 50 gram threshold of self confinement (Konski lecture series on Flash Attributes & Measurements). That's a damn rough figure but he was dealing with pyrotechnic applications and related measurements were fairly casual.

A Flare mfg site in Henderson NV had a terrible explosion resulting in one or more fatalities from their standard of KCLO4, Al, and a NC binder back some years ago. Flash is vicious due to a variety of reasons. One of them is that the Al becomes airborne and more easily subject to static. That's why one of the best improvements was to use enclosed tubes to distribute the materials; eliminating open containers and gravity mixing instead of contact mixing.




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[*] posted on 17-4-2011 at 11:11


Quote: Originally posted by Blasty  
Quote:
The ratios are Barium Sulfate 6, Aluminum (Dark Pyro) 3, Sulfur 1.


I recently tested this mix to see how it burned. Instead of using dark pyro aluminum, though, I used atomized (spherical) aluminum but in very fine powder (3000 mesh.) The thing is quite difficult to ignite, but once it does it flashes nicely. Sometimes the regular visco fuse I use just runs right through a small pile of the powder without igniting it (the ejecting gases from the fuse tend to scatter the flash powder and do not give it enough time to get hot enough for it to ignite.) A slower burning fuse helps avoid this from happening. Putting a little bit of granulated black powder on this mix it ignites readily even with the faster fuse.



I just finished some tests on this mixture but using strontium sulfate instead of the barium one. It is even harder to ignite. Not even putting a heap of black powder on it ignited it. The only way I managed to ignite it is by putting the flame of a butane lighter-torch on it until it was glowing orange-white for a while, then all of a sudden it ignited with a quick bright flash and a loud "THUMP!" If this mixture could be ignited a bit more easily it would make a very good and safe flash powder.
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[*] posted on 17-4-2011 at 11:38


There is a fascinating phenomenon that takes place in deflagration where the particulate gets smaller and smaller. Magnesium is a very good example. There is a point where the smaller particulate can "cake" or compress to such a degree that ignition becomes more difficult instead of easier. The demand for oxygen between the particulate (for flame initiation) reaches a point where one is almost attempting to "ignite a solid" unless the material is "fluffed" or brought to a point where oxygen can access the composition. Flame initiation is decidedly different that initiation via a detonation in extremely fine particulate. That threshold will differ in various compositions but it will exist in many, if the particulate is in the single micron (2-9um) size.



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[*] posted on 17-4-2011 at 14:20



I often wondered what the effect would be if a relatively large quantity of some flash composition was subjected to a long exploding wire(s).
If, say, a quanity of flash that was 4 inches by 4 inches had a number of thin wires threaded through it's bulk and all these wires were energised at the same moment (+ - some tens of mircoseconds) then 'all' of the flash would be 'going off' throughput it's bulk as opposed (if initiated with a flame) to travelling from one side/end to the other side/end.
Would this not have the effect of increasing 'the brisance' of flash my a large order?

Not pyro related I guess.

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[*] posted on 18-4-2011 at 06:05


Blasty:
I accidentally lost your comment it responding to it: apologies. But it DOES explain the Cab-o-sil issue indeed. You were right on track (IMO). Yes. anti-caking agents really DO have a positive affect. As do the use use of "spread" size spectrum ingredients. Whenever exampling a deglagration of DDT element, especially in a mechanical composition, you will see this agenda often raise it's head.




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[*] posted on 18-4-2011 at 06:21


I think that was my comment. Thanks though. That's what I had always assumed. Kind of counter intuitive when thinking about density and explosive propagation.



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[*] posted on 18-4-2011 at 09:39


Sorry, It was early in the morning and I was rushing around typing & looking at the clock.
I believe it was Konski (sp?)who either wrote and / or spoke of the need to work against materials compacting into a near solid due to particulate size. His example was rice hulls used in burst charges for entertainment fireworks but I supposed you could extrapolate that to most any per/chlorate flame initiated composition.
Personally, I have seen this myself. My personal experience was w/ magnesium. I had seen a design of a pyrotechnic that was fairly interesting (photographic flare genre') in that it used a two layer design similar to a Class B entertainment firework.
The thing had a burst charge made simply within a strong enclosure. The inner most layer containing a burst charge; the outer, containing extremely fine magnesium. The idea being that the burst charge would distribute the finely powdered metal in a small scale air-fuel explosion.
The technique was complicated by several factors. One of which was that the finely powdered metal alone often didn't ignite that well. It needed to be kept from compacting. The burst charge needed to be slow and substantially "flame-imbued". Black powder was actually the best form of burst charge as it spread a substantial amount of flame & was slow enough to allow the metallic particulate to spread just enough to catch.
The result for a SMALL design (3 grams - 1x3" outer tube; 1/4 x 2" inner) made a substantial blast, providing enough light to illuminate at lest 700 sq ft. It was very entertaining: the "fire ball" was about 15 sq ft and the noise was of low frequency & unique. Without a "fluffer" the metal would never spread to desired area. Rice hulls do very well with Al but Mg was best when interspersed with larger particulate of Mg, pyrophoric lead salts and cab-O-Sil. From an entertainment standpoint the noise and flash were very gratifying from a device that small.




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[*] posted on 18-4-2011 at 10:47


That sounds extremely beautiful.

*Runs to his workshop, inspired*

I also use BP coated hulls or hay for my burst charges. It always seems to give a better spread and I nice thump. I have never experimented with a magnesium dust cloud. Sounds amazing.

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providing enough light to illuminate at lest 700 sq ft.




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