Flash Safety - Bill Ofca on Flash

[Frozentech]

WHAT ABOUT FLASH?

 

Of all the thousands of variations available in the elements of fireworks, flash powder is perhaps the most spell-binding fascination to capture the attention of most pyros. Perhaps this is due to the high energy, awesome nature of its effects. The blinding white flash, sometimes followed by a cluster of titanium sparks, then followed by a gut tickling sound pressure wave, is somewhat exciting to say the least. The remarkable aspect is that flash powder is relatively inexpensive and simple to manufacture when compared to stars, for example. Fireworks makers (in the U.S.) use more flash and report components in aerial shells than any other single device or color.

 

When accidents involving flash powder occur, the high energy, violent performance of flash results in serious and catastrophic damage. In recent times, the legal as well as illegal fireworks trade has experienced the (high incidence) tragic loss of human life with almost all involving devastating flash powder explosions. The problems that lead to "accidental" disaster are all too common: complacency, carelessness, forgetfulness, apathy, contempt, and blind trust ("it won't happen to me, never has, therefore never will"). Those who fit this last category, the never-never people, cop a narrow minded attitude of "don't confuse me with facts, my mind is made up!" Notice that all these categories are products of the human mind: attitude and awareness. Can it then be questioned: are the "accidents" occurring from these problems really accidents? I think not. Irresponsible attitudes where safety is compromised can only be truthfully stated as negligence. When a bolt of lightning strikes the powder shed, - that's an accident;!

 

Lets examine some facts about flash and some safety tips on handling. A good quality flash has a critical mass of about 50 grams (less than 2 ounces). This means it will detonate with concussion in open air (no container), when ignited. Less than 50 grams will burn violently but without report. Compare this with black powder which has a critical mass of about 500 pounds!

 

A three inch aerial salute (2-1/2" X 2-1/2") containing about 4 ounces of flash, when ignited and if held in the hand, will dismember the human torso, not just a hand. Large salutes are very lethal;! The thought is rather horrifying, yet we must be realistic to understand the nature of the beast. Be thinking about this and the safety rules before you blend your next 10 pound (160 ounce) batch!

 

In a recent demonstration of the power of flash, a 1 pound bag was detonated electrically inside a wood structured shed. The blast and fireball was awesome! The shed was demolished with chunks scattered around where it once stood. Imagine 100 pounds of flash in an accident;! Instantly lethal in a 25 foot open air radius, and lethal up to several hundred feet if hit by missiles propelled from the blast. Windows will break for a 1/4 mile radius, and buildings will sustain structural damage to window and door frames up to 600 feet away. Buildings within 200 feet will sustain structural damage to framing timbers. Think about this: as the size (density) of the flash charge doubles, the force (or energy;) of the blast increases 8 times!

 

Here are some do's and don'ts on handling flash;:

 

1. Do mix outdoors only in humid weather .i.;(above 50% relative humidity;) to reduce the hazards of static electricity sparks.

 

2. Do wear only cotton clothing when mixing flash.

 

3. Do remove all jewelry and all metal including belt buckles.

 

4. Do spray yourself down and all tools, tables, etc. with Anti- Static Spray (aerosol cans). This material is amazingly effective in eliminating the chances of static electricity from ever occurring. I have personally tested this material while observing the results on a sophisticated electrostatic field strength meter. Anti-Static Spray is available in cases of 12 cans from Chiswick Trading, Inc. 31 Union Ave., Sudbury, MA 01776-0907. Similar material can also be purchased in super-markets and is known as Static-Guard laundry treatment spray.

 

5. Do screen all chemicals separately to remove lumps. Never screen flash powder after chemicals have been blended! The risks of friction ignition should always be avoided. A second and very real reason for avoiding screening any mixtures containing large quantities of conductive aluminum powder, is that the resulting aluminum dust cloud can and does generate static charges. Although humid conditions reduce the risk here, a life is not worth the risk.

 

6. Do mix flash on a large sheet of paper, rolling the pile of pre-screened chemicals as diagonal corners of the paper are lifted and pulled towards the center. (This is also known as the diaper method of mixing;). This method is common throughout the explosives industry (not just fireworks) and is practiced with making many types of sensitive explosives)

 

7. Do add the titanium last after most of the mixing of each batch is complete.

 

8. Do mix outdoors, isolated, away from people and buildings.

 

9. Do limit batch sizes to no more than 10 pounds (it's now an ATF regulation) or to the smallest batch needed to satisfy your requirements if less than 10 lbs.

 

10. Do limit to one batch and one worker in the work room when charging salute casings.

 

11. Do remove all charged casings from the work room to a magazine before introducing a new batch of flash to the same work room.

 

12. Do wear a dust respirator when mixing flash or charging it into salute casings.

 

13. Do clean up any chemical or flash powder spills immediately, especially if titanium is present.

 

14. Don't store bulk quantities of multiple batches in the same container, i.e. drums, etc. The larger the container, the heavier and harder to handle, which can result in catastrophic consequences if dropped.

 

15. Don't mix in plastic bags. (static)

 

16. Don't store in plastic containers!

 

17. Don't use plastic scoops or utensils - use only wood or aluminum.

 

18. Don't screen flash after blending chemicals. Never screen any formula with titanium present.

 

19. Don't mix, handle or use flash formulae containing potassium chlorate, especially if sulfur, antimony sulfide or titanium are included.

 

20. Don't mix indoors where aluminum dust suspended in the air can be ignited by the electric spark of appliances or light switches. The resulting blast has been known to level buildings such as in a gas explosion.

 

21. Don't smoke, even in a safe area, if your clothes are contaminated with flash powder.

 

22. Don't expose too many workers to flash operations. Limit the number of workers to only those necessary to complete the assigned task (usually 1 or 2). Keep all operations in separate sheds or limit one work room to one operation at a time. -W.O.

[nickle]

I want to thank you for posting this even though I don't use flash or think I ever will. I've downloaded and printed this essay in nice big letters and posted it on the wall behind my work bench.

 

This is a reminder to myself as to what can go wrong when we get a little too complacent, and think this can't happen to me.

[PyroMedia]

Please point out anything incorrect but couldnt flash powder be mixed in a mall mill without the media? it seems like the diaper meathod to me, espically with those lorotone tumblers with the soft rubber barrels.and you wouldnt have to be anywhere near it while mixing. and airborne dust could be solved with a little bit of water mist sprayed on the comp.

This seems like a good way for small quantities (under 50 grams) With harbor freight models you can have the container not properly secured on (without the nut) so if an explosion did occout the lid would just pop off without too much pressure.

Edited September 14, 2008 by PyroMedia

[Mumbles]

I think static is normally the factor that people tend to shy away from that make that method unpopular. It is actually commonly done on much larger scales in commercial manufacturing. 200lbs at a time in a modified cement mixer remotely. If you can get an area far enough away from anything else it may be useful, but without that it's exceedingly dangerous.

 

FYI, it is going to go up like a bomb if it does go off, because that is essentially what it is. A jar, no matter how loose the lid is will be enough to self confine it.

[Richtee]

FYI, it is going to go up like a bomb if it does go off, because that is essentially what it is. A jar, no matter how loose the lid is will be enough to self confine it.

 

With a hot mix it will not matter if it's in a 5g pile on the ground. BaLOOOIE.

 

Wow cement mixer full of flash? LOL!

[PyroMedia]

true, but if your using a rubber barrel, like a lorotone, that more or less kills static dosnt it?

[TheSidewinder]

I wouldn't count on it......

[Miech]

That rubber barrel is isolated quite well grom the ground, and especially when my lortone was standing in the sun I've noticed the barrel can get quite static. You'll probably never get a shock from it, but it was enough to be measured by a relative insensitive homebrew static detector.

[PyroMedia]

Time to go do some testing. good thing i have like 3 lorotone tumblers.

[Mumbles]

Whatever happened to "I'm not going to be making any flash for a long time"

[Richtee]

Whatever happened to "I'm not going to be making any flash for a long time"

 

In my youth, 12 hours was "a long time". Sigh.

[PyroMedia]

Slow Flash for boosting shells. I cant get Kclo4 here. Edited September 20, 2008 by PyroMedia

[billofca]

I think static is normally the factor that people tend to shy away from that make that method unpopular. It is actually commonly done on much larger scales in commercial manufacturing. 200lbs at a time in a modified cement mixer remotely. If you can get an area far enough away from anything else it may be useful, but without that it's exceedingly dangerous.

 

FYI, it is going to go up like a bomb if it does go off, because that is essentially what it is. A jar, no matter how loose the lid is will be enough to self confine it.

_______

 

Please, please, my fellow pyro guys, NEVER, mix flash in any kind of machine or tumbler! Only the diaper method on paper is safe. I once had a devastating explosion on June 4th, 1980 mixing 50# of flash in a modified cement mixer where the blades had been removed and the motor changed to an explosion proof non-ventilating motor. Powder leaked into the seams of the drum and was pinched by the weigh shifting of powder as the drum rotated. Windows broke for 1/4 mile radius to the plant costing $10,000 to replace. Commercial FW companies do not use mixers; they only use the diaper method on large sheets of Kraft paper. - Bill Ofca

[fredhappy]

Very good information, thanks!

 

Bill, I have a question concerning that accident which you describe. What kind of flash powder was involved? Standard 70/30 pot perc/dark al, or a formulae with added sulphur?

 

friendly pyro greetings,

[optimus]

Bill, I have a question concerning that accident which you describe. What kind of flash powder was involved? Standard 70/30 pot perc/dark al, or a formulae with added sulphur?

 

Bill doesn't post here (AFAIK anyway) - Frozentech was quoting a chapter from his book.

 

EDIT: I'm an idiot. Note to self: review topic before posting to avoid loooking like an idiot. Hi Bill

Edited October 27, 2010 by optimus

[dagabu]

Commercial FW companies do not use mixers; they only use the diaper method on large sheets of Kraft paper. - Bill Ofca

 

Bill,

 

What about Albert Knobloch from Little Big Shots? He screens all of his flash and has done so for decades commercially. Dan Mike Row from Dirty Jobs did an episode of making flash this way.

 

Dave

Edited October 28, 2010 by dagabu

[Dr Boom]

Dave- I was just about to post that, I've mixed flash on screens for years without incident.

 

And while there are accounts of people hitting their finger nails along a screen with enough force to set off the flash- those are few and very far between.

 

Now, maybe all that means is I've been darn lucky over the years- and so has everyone else who uses screens... maybe it doesn't and screens are quite safe. Should that be a point of contention here? Meh, I'd say no because working with flash (to any degree) is not for the novice nor fool-hardy. IF and WHEN you are ready for flash, don't go right for the 6" can salute, however tempting it might be. Start small and gain confidence.

Even for the bigger items; if you are not comfortable making a large batch at once, do several small ones and keep them all seperate until the last moment of construction.

 

Of course I'm not going to discount Bill's plug for the diaper method either- has anyone EVER heard of that setting off flash?? Didn't think so...

 

Static electricity is a nemesis we must learn to control and never take for granted.

[Ralph]

Bill,

 

What about Albert Knobloch from Little Big Shots? He screens all of his flash and has done so for decades commercially. Dan Row from Dirty Jobs did an episode of making flash this way.

 

Dave

 

mike not dan just fyi

[dagabu]

LOL! I have a buddy I hunt with named Dan Row, I do that all the time.

 

Correction: Mike Row

 

Dr. Boom-

 

IMHO any mixing of flash, including binary mixing has inherent danger as does diaper mixing since the dry powdered aluminum can and will generate static under certain conditions. In any case, friction and static are enemies of flash and a very light coating of an anti static spray can all but remove the static problem where as a paper scoop method of dispensing would make generating enough friction unlikely.

Edited October 28, 2010 by dagabu

[billofca]

Very good information, thanks!

 

Bill, I have a question concerning that accident which you describe. What kind of flash powder was involved? Standard 70/30 pot perc/dark al, or a formulae with added sulphur?

 

friendly pyro greetings,

 

It was a standard 70/30 mix, no sulfur, potassium perchlorate/aluminum using dark aluminum 400 mesh. The analysis of the accident determined powder had leaked into a seam of the drum and as the drum rotated, the powder would slide, tumble and shift weight inside the drum causing distortion of the drum and pinching of the perchlorate. A piece of the large gear on the back of the drum was found 1200 feet away in someone's back yard tomato garden. The center shaft of the drum was found sticking through the side of a trailer magazine 500 feet away. Every light bulb on the plant was broken with structural timber damage to sheds up to 400 feet away. I heard the explosion 20 miles away, it sounded like thunder on a clear blue sky day. My business partner was running operations on the plant that day. Less than a minute after the explosion I was called. By the time I got to the plant, there were 3 police agencies, the fire department, and various news reporters and camera crews on the scene. There was a hole in the ground 2 feet deep and 12 feet in diameter where the mixer was. I can't begin to tell you the bad publicity, embarrassment, and PR problems we suffered from that incident. We were fully licensed so there were not legal repercussions. A valuable lesson was learned that day. Machines can't handle fireworks mixing.

[billofca]

Bill,

 

What about Albert Knobloch from Little Big Shots? He screens all of his flash and has done so for decades commercially. Dan Mike Row from Dirty Jobs did an episode of making flash this way.

 

Dave

 

Dave, I have also used screens to mix flash. The point being in my previous post is that the diaper method on paper is the safest method. Perchlorate (and only perchlorate) needs to be first screened to take out any lumps. I used cotton gloves (no static) to push the perchlorate through the screen. The screen was made of brass. Then the perchlorate was added to aluminum on the mixing paper and the flash was rolled on paper (diaper method) many times back and forth. After mixing on paper, I screened the entire batch of flash by shaking it through the screen 2 times. SHAKING, not rubbing. The flash was collected in a cardboard box under the screen. Then the flash was placed on the diaper mixing method paper and 5% sponge titanium added and rolled into the mix. The flash was then put into a box with a cover (box top) and put into a magazine before the next batch was started. Review my safety rules especially regarding static protection and humidity.

[dagabu]

I cant find fault with your method Bill but I am wondering why the cotton gloves while screening the perc? It has a flammability rating of 0 on my MSDS and needs a fuel to burn. Also, it is an irritant to the skin so I use nitrile gloves.

 

I do like the reminder to use a cardboard box but the use of an anti static bag is fine as well. I use the antistatic pink bags from Uline.

[fredhappy]

Geesh, I understand what happened. I guess that just sums it up for mechanically mixing flash powder.

 

The one thing that is on my mind is : what about when you close your shell. I am used to making flashbags . I just don't feel very comfortable chucking the flashpowder on top of the rice hulls and slapping the two halves together. Would it

be possible to have this pinching of the perchlorate if I would choose for the loose flashpowder route instead of using flashbags. I am not very pleased with the ( small) delay the flash bag gives my shell. I add another layer

of paper on the flashbag, so that it is somewhat cushioned for any stress during the closing of the hemis.

 

I would be very interested in your opinion regarding this construction dilemma for me. Safety wise, should I stick with flashbags, or would the friction stress of closing the hemis not be enough to accidentally cause a catastrophe whilst

closing my shell?. I hear different opinions all the time. One person told me that the Chinese just dump the loose powder on top of the ricehulls. He did however stress not to be too rough when closing the shell... ...

 

Thanks a lot for your opinion, I ve read tons of stuff you wrote, it would be great to hear what you think about this. It is such common place to just dump your flash on top of the ricehulls, but I ve always wondered if an accident

might occur from this practise.

 

I've enclosed a picture of one of my black titanium salutes which I do like to boost with some flash. That gives you and idea about how I am currently constructing my flashbags.

 

friendly pyro greetings,

Edited October 29, 2010 by fredhappy

[billofca]

Geesh, I understand what happened. I guess that just sums it up for mechanically mixing flash powder.

 

The one thing that is on my mind is : what about when you close your shell. I am used to making flashbags . I just don't feel very comfortable chucking the flashpowder on top of the rice hulls and slapping the two halves together. Would it

be possible to have this pinching of the perchlorate if I would choose for the loose flashpowder route instead of using flashbags. I am not very pleased with the ( small) delay the flash bag gives my shell. I add another layer

of paper on the flashbag, so that it is somewhat cushioned for any stress during the closing of the hemis.

 

I would be very interested in your opinion regarding this construction dilemma for me. Safety wise, should I stick with flashbags, or would the friction stress of closing the hemis not be enough to accidentally cause a catastrophe whilst

closing my shell?. I hear different opinions all the time. One person told me that the Chinese just dump the loose powder on top of the ricehulls. He did however stress not to be too rough when closing the shell... ...

 

Thanks a lot for your opinion, I ve read tons of stuff you wrote, it would be great to hear what you think about this. It is such common place to just dump your flash on top of the ricehulls, but I ve always wondered if an accident

might occur from this practise.

 

I've enclosed a picture of one of my black titanium salutes which I do like to boost with some flash. That gives you and idea about how I am currently constructing my flashbags.

 

friendly pyro greetings,

 

The Chinese put a bit of flash on top of their rice hulls in 3 inch shells. I recently opened 25 three inch shells and they all had about a half teaspoon of flash in with the rice hulls. I don't think its a problem or we would have heard about a lot of Chinese accidents. The mechanical energy of crushing potassium perchlorate in a rotating drum pinching the flash that leaked into the seams is a lot greater than anyone can produce when closing two hemispheres of a shell. I wouldn't worry about that. Here is a related story. I remember one time I was digging into a 200# drum of perchlorate with an aluminum scoop (a big one). The perchlorate had hardened into very large chunks, and I was stabbing at the chunks to break them up. Then I took a huge scoop of the perchlorate and drew the scoop out of the barrel. As the scoop passed the rim of the barrel top, a huge blue electric spark jumped from the scoop to the barrel lid opening rim. There was no danger there as it was only potassium perchlorate, but it got me thinking. I could only conclude in my head that it was piezo-electric charging (not static). Piezo electric occurs when crystals of quartz are struck and compressed, such a a gas grill push button lighter does to do an electric spark ignition. A spring loaded hammer strikes a quartz piezo generator. The drum of the perchlorate had a plastic bag liner, insulating it from the perchlorate. It in effect became the plate of a capacitor, and the metal scoop was the other plate. Stabbing at the chunks of perchlorate (I think) produced the piezo-electric charging. Just a theory that I would like to test some day with the proper lab instruments. It would definitely explain why perchlorate is impact sensitive in explosive mixtures. It also explains why the cement mixer exploded. I used cement mixers again for star mixtures (never flash) after that accident but the seams were braze sealed on the inside of the drum before they were used. Flash bags are okay but will blow stars blind most of the time unless they are spider web stars. Try my slow flash mix, it works pretty good. It's published in TIF #2.

[dagabu]

Sorry Bill, the only Potassium Crystal that is a piezo generator is Potassium Niobate (KNbO₃), but since tendons, bone and silk do have piezo tenancies, perhaps your tests of whole crystals would yield and electrical charge.