Flash Powder Safety

[Swede]

umm, I would stop befor you kill your self cause that is exactly how flash is going to be set off. someone correct me if I'm wrong but I have like read this every where that it should "NEVER BE SCREENED OR BALL MILLED".

 

I tend to agree. Nothing wrong with screening the components SEPARATELY, especially the perchlorate which can tend to clump, but watch out for contamination; keep things clean. A brush on a screen gives me visions of static build-up, especially if the screen is in a wood frame and ungrounded.

 

FP is best diapered.

[Mumbles]

If you couldn't get flash to go off with friction, you wern't trying hard enough. I can get it to start snapping without a great deal of trouble in a mortar and pestle.

 

I definitely wouldn't be using a brush on the flash, or a screen that fine. It's a commonly practiced commercial process to "screen" flash. Screen must not be confused with what is done with other compositions. Generally the components are mixed by diaparing, and then passed through a 40 mesh or so screen. Light tapping on the screen is all the more force that should be used to make it pass. It helps to break up any clumps or pockets that may have formed. Think of it more as a sifting than a screening. I've seen powders that have been screened through 200 mesh screens, and that stuff is scary powerful. Way more than is ever needed for normal pyro. That stuff had a specialized application however.

[Seymour]

I'm one of the ones who would rather make a hundred grams once than ten grams ten times.

 

I believe my mixing process is as safe as you can get without using a contraption to mix it remotely.

 

Firstly I pass the powders separately through a 120 mesh screen on to a large sheet of paper. The Aluminium first, and the perchlorate on top of it, though I doubt this detail is hugely important. I then diaper it (lift the corners one by one to 'fold' he powders together) until it appears homogeneous, and then do it more. The powders are so fine that there is going to be an awful lot of mixing that one can not see.

 

Now I try to load it all in to shells and salutes to avoid storing it.

 

As for the screens, I've heard that horse hair screens are the safest ones for screening whistle, flash and other nastiest, though with the wet (other solvents, not actually water) process producing such good whistle, so safely, I'm not sure why you'd try to screen it!

[50AE]

I think the diapering method is best for small batches. Someone have mentioned before that cardboard drums are used for large quantities needed in firework factories.

I have the habit to mix small batches, 10 grams usually, only when I need them.

Edited May 7, 2009 by 50AE

[Agni]

Greetings from India.

Although I have some family History in Fireworks/Pyrotechnics, I am only getting started now.

I am here to Learn and be SAFE while at it.

Here in India, the Potassium Nitrate Flash Mix(Potassium Nitarate : Sulfur : Aluminium Powder in the ratio 5:3:2) with 1-2% Boric Acid, is the most popular method of making Flash for loud reports.

The method/procedure is as under -

1. Take a piece of pre-cut cardboard(3.25' x 2.25') and fold it to make it into a rectangular box.

2. The bottom and sides are pasted with Dextrine and the cardboard box is filled(2-4 grams) with the above Flash Powder and then the top too is closed and pasted with Dextrine.

3. Next, the box is wrapped up and packed in a piece of newspaper of appropriate size in order to prevent any Flash Powder from leaking from the Cardboard Box inside.

4. Now, the most important part to which my questions will pertain to. This box is now immersed in a solution of Dextrine and then put to dry in the sun until it becomes stiff & hard on the outside.

5. Once it's dry it is wrapped up in Hemp String(Sutli) from corner to corner 5 times and once again dipped in the Dextrine solution and left to dry in the sun till it is hard.

6. Once dry, a hole is made in it with a needle/spindle right through the 5 layers of hemp and the cardboard box and a fuse is inserted and glued/primed with Black Powder.

7. The last step is to cover up the Hemp in Colurful Foil Paper in order to make it look attractive and the Fuse is safely wrapped around it.

As stated in Point No.4 "This box is now immersed in a solution of Dextrine and then put to dry in the sun until it becomes stiff & hard on the outside. " This is done in order to ensure that the box is tightly packed so that even If it is loosely wrapped up 5 times in Hemp String/Fiber, there shall still be a Loud Report.

My questions are as under -

1. By immersing the Flash filled box in a solution of Dextrine and putting it to dry in the sun, is there a risk of Spontaneous Ignition? Deflagration? (Are we creating an external pressure on the Flash Powder inside? )

2. Since there is every possibility of the Dextrine solution seeping inside and mixing with the Flash Mix, what are the chances of Ignition ? Especially when this box is left to dry in the sun for hours.

3. Further, once the box is dry it is wrapped up in Hemp String(Sutli) from corner to corner 5 times and once again dipped in the Dextrine solution and left to dry in the sun till it is hard. Is this adding to Spontaneous Ignition Problem?

3. What can be done to avoid it and make the entire process safer.

[schroedinger]

The dextrine liquoer shouldn't pose any risks there, but if it comes into contact with the flash and binds it, it can render the flash useless.

 

You are far better off, using the traditional german way of making such cubes. You take a precut carton that can be folded into a box (look a little like a T, made out of 6 segments of equal size, 4 long and the T-bar 3 wide. It needs to have flanges for gluing it together. Fold it into a cube, leave the top open. If you have good fuse that can stand a little moisture, glue it into the top now (better not to poke into flash with an ale). Now add the propellant (Corned B.P., H3, Flash). Shut the top, ans wrap 2 times with gummed Tape, in each direction (x, y, z axis). Now let dry and do the same with pasted string. Let dry. Now the cube is ready, or it can further strenghtend by dipping in paste, paste + waterglass or molten colophony resin.

[Ubehage]

I found this video of "Dirty Jobs", where he works as a fireworker.

 

In this episode, they mix flash BY HAND through a screen!

Everything I have learned, tells me that they are idiots. But, it is a professional fireworker...

What do you guys say?

(They begin at 4:05)

https://www.youtube.com/watch?v=u1x12nASDXo

[schroedinger]

Well screen mixing flash is quite normal in industry, and there are many amteurs who do the same. The good thing about it is, that you only mix the flash one time and still can process a big ammount. But yeah the way they do it looks quite dangerous. I would never use a sieve in an iron frame, that stands on the paper where the flash is falling at and pushing the flash though the screen like a normal comp also isn't the best way, but appart from the first point i don't think that it is unsafe in any way.

In industry there where also "ball mills" that just employed an empty barrel (no media only the chemicals) turning at about 5 rpm to mix flash.

[Mumbles]

Screen mixing is probably the safest and most effective way to mix large quantities of flash. I know it seems contrary to common sense at first. It's pretty well known among the fireworking community, but also not well publicized. I've always felt that's its to prevent bad ideas, or people attempting it without proper training. It's not difficult, but it's one of those things that's really better passed on in person in my opinion.

[OldMarine]

I've not understood the danger of screen mixing flash. It would seem that as long as you're not scrubbing it through but only sifting and maybe using a soft brush it would be as safe as diapering.

I haven't made any yet but I'm sure I'll want it before long for rocket headers.

[Seymour]

I think screening is not recommended for initial experiences making flash because of the risk of the maker scraping something on the screen, or using too much force. These risks are there with star mixes too, of which many are nearly flash sensitivity and some the same or more sensitive than flash. However you don't live if 200g flash goes off on you, but 200g star mix may be "only" badly burned.

 

The consequences of a flash accident are so serious that extra measures that are somewhat disproportionate to its sensitivity are justified. I feel that people sometimes feel like the consequences of a flash explosion are matched in level of intensity by the sensitivity of the mix. thankfully this is not the case and it can be handled quite safely with enough care and knowledge.

 

Ubehage, I've personally screened hundreds of kilos of 70/30 now. Yes I do it carefully, but that also applies to compositions in general.

 

Standing there with 25kg flash in one pile is an experience at first, but you get used to it

[MrB]

and maybe using a soft brush

 

Just be aware that most soft brushes are prone to generate static charges.

 

Anyway, the biggest issue i bring with me from that episode of dirty jobs is the lack of eye-protection.

B!

[schroedinger]

Not only the lac, of eye protection, look when they roll the stars, he is black and a little later removes the dusk mask an you can seenhow good these paper mask are, even under it he is black.

Also i find it interesring when he complains about his eye hurtingn and get told that comes from the dextrine in the mix, well I'm pretty sure the dextrine is the stuff least present in the mix and not what causes the problem.

[Seymour]

This is a bit off topic, but I'm not sure if it's worth a whole new thread.

 

Does anyone have a mask that completely prevents all of that dust? I've been using one that the safety shop said was the very best for particulates and was fitted to the shape of my face. When doing "heavy dust" work, such as screening 10kg of ball milled charcoal some of it inevitably gets in, I assume through tiny gaps in the seal. While obviously I am very appreciative of the 99.something% of the dust that it keeps out, it's not that great a feeling having somewhat black snot after wearing it.

 

When things are super super dusty I try to hold my breath during the worst of it as well as wearing the mask.

 

I feel like a positive pressure suit would be ideal, but obviously not practical for most pyros.

[BlueComet24]

For BP chems, I just wear an N95 particulate filter. When dealing with more toxic chemicals, I wear a P95 organic vapor respirator. It seems to keep out all dust except when I'm moving my head around a lot (because of small gaps that may temporarily form around the edges of the mask where it fits to my face). Also, because it's sealed with rubber to my face, it doesn't fog up my goggles or glasses, which is another plus.

[dynomike1]

Well i do 7 ounces at a time i put each chem in a stainless thermos and roll it around. Seems mixed good enough.