Flash mixing

[nater]

I disagree completely. Mixing 2kgs of flash at once!!! Are you mental!?

His words are wise and he has all 10 fingers too. Something to think about, if the riskiest part of an operation is mixing, then limit the number of times you perform it as much as possible to reduce the risk.

Edited October 26, 2013 by nater

[Mumbles]

100g will make you just as dead as 2000g. It's far safer to mix one large batch than multiple smaller ones. Even for one moderate sized shell, a kilo of flash is not unreasonable. I typically would make all of my bottom shots and salute inserts in one day. If I were to build three 5" multi-break cylinder shells, that's conservatively 5lbs right there. The binary method works for some things. Bottom shots, or (in my opinion) anything resembling a safe or structurally sound report insert are not one of them.

[pyroman2498]

Would it be safe to weigh the flash after mixing ? like in a paper cup, say im making inserts for a ring, and i want the bangs/ pops to get louder as the ring goes around, if this makes any sens. im not planning on doing this but i do get this question a bit by PM so i thought i would ask . I dont use flash anymore , and dont plan to till i get more experience with building regular shells first.

[pyrojig]

weighing would be no prob. if you reduce the dangers of fire and static from outside sources. Your idea is interesting , but diff, weighted inserts will have a non-symmetrical burst . The heavier ones will fly further . Flash is a wonderful comp if used properly , and safely. It is a incredible booster for small shells, and is the industry standard for most smaller shell manufactures . There is a load of hype about the dangers of flash, and lots of good info. I agree , that one should get due experience first before working with more energetic materials . There is a reason most moderators will steer a "noobie" away from it. Its power is greatly underestimated by inexperienced people, and this can lead to loss of digits or worst. But if one where it treat it with respect and has some experience building pyro devices ( not boomers) then I would say work with it in smaller quantities and learn its ability to boost shells .

[cogbarry]

In relation to using the WASP, could you please explain in more detail your technique to install the blackmatch and keep it in place in the tube while pasting on the WASP . Is the blackmatch just a tight fit and pre-positioned so the ends end up flush with the time fuse that is installed after pasting? Recently got a WASP and am researching fusing techniques.

 

I take a piece of fast paper firecracker fuse, the kind that has a few strands of BM in it. I use masking tape and put one continuous wrap towards one end until it fits snug in the passfire tube, leaving some of the fuse above this wrap that will actually end up near the center of the shell. I peel the paper off the bottom end of the fuse, exposing BM. I then insert it into the passfire tube with the warp of tape about halfway into the passfire and tape it to the passfire tube with another wrap of tape, leaving some BM hanging out the other end of the passfire. I then pack the peeled BM into the passfire and glue the passfire to one hemi as usual, using a dowel or something as a jig to line it up with the hole in the hemi. If the depth of the open side passfire is deeper than desired, I simply pack more match in.

 

This is admittedly, a crude hack, it can probably be done with other methods, maybe with a kraft paper wrap on the inside end of the passfire, some string, clove hitch? Then again, I prefer a method in which I'm confident, seals the inside of the passfire from the inside of the shell (no flash leaking into the passfire).

 

You are still penetrating into a passfire with BM. If you were to generate a spark (maybe by your two magnets slamming together, static, etc), you could still ignite the shell. I'm just more comfortable when I don't have to remove magnet, fuse, etc with an open penetration to the now mixed flash.

[ollie1016]

100g will make you just as dead as 2000g. It's far safer to mix one large batch than multiple smaller ones. Even for one moderate sized shell, a kilo of flash is not unreasonable. I typically would make all of my bottom shots and salute inserts in one day. If I were to build three 5" multi-break cylinder shells, that's conservatively 5lbs right there. The binary method works for some things. Bottom shots, or (in my opinion) anything resembling a safe or structurally sound report insert are not one of them.

Some people will have different views and ideas from the amount of experience and knowledge they have. I personally never mix over 20g at one time. The only exemption to this is if I am making a large salute shell in which I use the binary method.

 

I've gone back to using KNO3 flash at the moment, I feel it gives a deeper, lower pitch 'boom' that can be more impressive.

[psyco_1322]

Oh just screen it and be done.

[JayDee2]

Re fusing. Thanks for the info cogbarry. Always good to learn of other people's solutions and techniques.

[jerronimo]

So basically the "binary method" means putting the ingredients inside a cardboard tube and shaking it vigorously? Wouldn't it be safer using a machine to shake it?

Makes no difference in terms of incorporating the oxidizer and fuel.

The advantage of using the binary method is that you won't be handling ''live'' flash in the open.

It helps to add 1% of SiO2 to the oxidizer and premix this in a ballmill or coffee grinder to make it free flowing.

When you use a machine to mix it you still need to handle the ''live'' mixture in the open where it is susceptible to static and friction.

 

If a shell filled with flash can survive the shock from lift, it will certainly survive shaking and handling.

Hell, millions of fireworks are exported from China every year, and most of them contain flash in one way or another.

[Seymour]

 

Mixing 2kgs of flash at once!!! Are you mental!?

Surely we all know that we are somewhat insane?

 

 

Oh just screen it and be done.

Agreed!

 

I find that screening over ten kilos at once is a bit difficult with the screens I use, so while I try and do it all in one batch, if I need a lot, I'll do it in several batches of 5-10kg.

 

In case someone is reading this without having read about screening flash, it should be done as gently as possible. Typically the oxidizer is screened separately to break up any lumps. Then a little Aluminium is screened with the perchlorate and sometimes a little perchlorate with the Aluminium, before the two are fully mixed.

[Mumbles]

There is definitely a different technique to screening flash. It might sound crazy, but it's honestly the only safe way to mix large quantities of it. I really don't recommend anyone try it without being visually shown the proper technique. It really is different than screening star compositions.

[cogbarry]

There is definitely a different technique to screening flash. It might sound crazy, but it's honestly the only safe way to mix large quantities of it. I really don't recommend anyone try it without being visually shown the proper technique. It really is different than screening star compositions.

Can you elaborate a bit on this? I was told this should be done with a 40 - 60 mesh stainless screen and wooden spoon but I didn't know the technique was different.

[Mumbles]

The way I was shown is really more of a sifting than what I'd typically think of as screening. I even get a little uneasy pressing the last little bit through on the first pass. I generally will diaper the mix to roughly integrate the flash, and then give it a final pass or two through the screen. You'd be surprised at how poorly diapering actually mixes flash.

[cogbarry]

The way I was shown is really more of a sifting than what I'd typically think of as screening. I even get a little uneasy pressing the last little bit through on the first pass. I generally will diaper the mix to roughly integrate the flash, and then give it a final pass or two through the screen. You'd be surprised at how poorly diapering actually mixes flash.

 

Thanks,

I've been told by another pyro that screening really is the only way to mix flash well. I know that some of the claims of the sensitivity of flash have been exagerated. The idea of screening still makes me nervous though.

 

I would think that if you screened the oxidizer through a fine screen first, you could avoid having to push the comp through the screen. Correct me if I'm wrong but I don't think you need to use a real fine mesh for mixing. I use a regular kitchen strainer for most of the other comps I mix.

[Shadowcat1969]

The way I was shown is really more of a sifting than what I'd typically think of as screening. I even get a little uneasy pressing the last little bit through on the first pass. I generally will diaper the mix to roughly integrate the flash, and then give it a final pass or two through the screen. You'd be surprised at how poorly diapering actually mixes flash.

So something like a gentle shaking back and forth?

 

I think maybe screening the first pass or two with 5 or 10% of the aluminum in all the oxidizer? That way when you have to push that last little bit through in the first pass it won't be at an ignitable state, but the initial mixing would allow for the perchlorate to not clump up again. Does that sound like a reasonable idea?

[psyco_1322]

Yeah that's a good technique. It doesn't take hardly any Al to anti-cake the perchlorate, maybe a gram. Just screen them a time or two, I always go a second time with the oxidiser to get it good and mixed it. Then add in the remaining Al and "shake" it through the screen. You should not be touching the chems, or in any way forcing them through or around in the screen. I go ahead and screen the mix 3 times to get it well mixed, but I'm sure that once or twice would suffice for making the stuff work.

[Mumbles]

I would normally screen the perchlorate itself through a 60mesh screen, diaper with the Al, and then sort of sift through a much coarser screen (20-30 mesh or so). Even with the pre-screening, there was always a little bit that needed a little gentle coaxing through. With that, I just sort of flatten it against the screen, and that did the trick. Maybe pre-screening a little Al would help, but it's really not a big deal.

[cogbarry]

I did follow a tip I read from Ned G on pre-screening 5% Al with the Perc. I do this when binary mixing and from what I've seen so far, it does solve any clumping issues.

[countryboy7978]

Some people will have different views and ideas from the amount of experience and knowledge they have. I personally never mix over 20g at one time. The only exemption to this is if I am making a large salute shell in which I use the binary method.

 

I've gone back to using KNO3 flash at the moment, I feel it gives a deeper, lower pitch 'boom' that can be more impressive.

 

I know I only have 15 posts here but I've been at this for over 15 years.

 

Mix the amount you feel comfortable mixing but keep in mind if you are filling more than a few small reports or one larger report, you will be exposing yourself to the mixing process more than necessary. While the law of averages plays into this to a certain degree (the more times you mix the greater the chance of an accident from static, etc.), I feel that if you have to mix 20, 100 gram batches to make 20 shells you will grow fatigued and possibly complaisant. That is where the danger lies. You start to get bored, or worse bold and do things you otherwise wouldn't do if it was your first and only batch. Mix once, fill all your casings and seal them in one sitting, clean up any spills properly and be done.

 

I didn't always do things this way, but the more you work with energetic materials and the more you learn from other pyros the more knowledgable you become.

 

Thanks Nate for the props. Surprisingly yes I still have all my fingers

Edited November 4, 2013 by countryboy7978

[LambentPyro]

I know I only have 15 posts here but I've been at this for over 15 years.

 

Mix the amount you feel comfortable mixing but keep in mind if you are filling more than a few small reports or one larger report, you will be exposing yourself to the mixing process more than necessary. While the law of averages plays into this to a certain degree (the more times you mix the greater the chance of an accident from static, etc.), I feel that if you have to mix 20, 100 gram batches to make 20 shells you will grow fatigued and possibly complaisant. That is where the danger lies. You start to get bored, or worse bold and do things you otherwise wouldn't do if it was your first and only batch. Mix once, fill all your casings and seal them in one sitting, clean up any spills properly and be done.

 

I didn't always do things this way, but the more you work with energetic materials and the more you learn from other pyros the more knowledgable you become.

 

Thanks Nate for the props. Surprisingly yes I still have all my fingers

You make some good points here. When I get bored, I make myself step away so I don't skip over any precautionary measures that I could possibly forget.

[psyco_1322]

 

I know I only have 15 posts here but I've been at this for over 15 years.

 

Mix the amount you feel comfortable mixing but keep in mind if you are filling more than a few small reports or one larger report, you will be exposing yourself to the mixing process more than necessary. While the law of averages plays into this to a certain degree (the more times you mix the greater the chance of an accident from static, etc.), I feel that if you have to mix 20, 100 gram batches to make 20 shells you will grow fatigued and possibly complaisant. That is where the danger lies. You start to get bored, or worse bold and do things you otherwise wouldn't do if it was your first and only batch. Mix once, fill all your casings and seal them in one sitting, clean up any spills properly and be done.

 

I didn't always do things this way, but the more you work with energetic materials and the more you learn from other pyros the more knowledgeable you become.

 

Thanks Nate for the props. Surprisingly yes I still have all my fingers

 

 

That is a very good point. After repeating a process so many times, you tend to become more sloppy as you go about it. Plus there is no reason to make a separate batch for each it shell, you can just as easily screen half a kilo as you can 100g. It's not that flash is more sensitive than other comps, it's the fact that if something is to go wrong, the outcome is going to be much worse.

[Sammikins]

Use the diaper method! It's very safe, and low risk. Pour both chemicals on a piece of paper and just fold one way, then fold the other. Keep doing this until is is fully mixed(uniform color).

[cogbarry]

Use the diaper method! It's very safe, and low risk. Pour both chemicals on a piece of paper and just fold one way, then fold the other. Keep doing this until is is fully mixed(uniform color).

 

This is how I have mixed in the past when not binary mixing. However, I considered it my variation of the diaper method. I think that the definition of the diaper method is lifting alternating corners of the paper, not folding it.

 

This method is faster and IMO mixes the two components better. Not sure how it compares in terms of safety, I use my hands/fingers to sort of mush the components together so I'd say it puts more pressure on the mix.

 

I know that many pyros, including at least one that manufactures commercially screen their flash and in large quantities. IMO, it's the precautions for static/low humidity, not mixing near anything electrical that could spark, sticking with the more stable comps, not slamming/dropping things, etc, that is important.

[dagabu]

Use the diaper method! It's very safe, and low risk. Pour both chemicals on a piece of paper and just fold one way, then fold the other. Keep doing this until is is fully mixed(uniform color).

I once was told that "diapers are for babies, not flash".

 

My case in point was 200 inserts that didn't light because of a non homogenous flash mix. Opening several and screening the mix resulted in a robust amd easily lit mix in the inserts.

 

My personal opinion is to screen it like Mumbles does, make enough to finish your project so you don't have extras sitting around.

[cogbarry]

I'd still recommend using the diaper or binary method until one has a couple years of experience with pyro in general.

 

I'd also add that a good non ferrous/non sparking screen be used. Fine screens for individual components, course screens for mixing. I need a good set of stainless or brass screens myself.