Safest way of mixing TPA based flash?

[Czx7]

Im looking at making some TPA flash and I was going to default to just using the diaper method as that is the a tried and true method. I was wondering if with the decrease in shock and friction sensitivity of TPA flash would it be safe to just screen the chems together or would that be unwise. If there is a quicker and more effective method that the diaper method please share. Thanks.

[Carbon796]

The safest way, is clearly going to be the diaper method. 

Can you screen it, sure. But, I also routinely screened mixed 8:3:2. 

True TPA based flash. When properly processed, was a granulated product. It is at this point, where it was proposed to be a safer to handle product.

In larger quantities, in power form it's possible for it to self contain. 

Edited October 1 by Carbon796

[Czx7]

Thanks for the input. I don't plan on making more than 100g at any given time so I don’t think self confinement is a problem.

[pyrojig]

There is always the closed container / shell mixing approach. All unmixed components are added , container closed and during the movement of or pasting, the container it is in makes a complete mix

[Czx7]

By movement do you mean like a small star roller that tumbles the mix?

[Carbon796]

He's talking about the binary mixing method. For small ball shells or rocket headings. The " container " is the shell hemi's themselves.

Is there a particular reason your wanting to make TPA based flash. It's only real advantages are " safer and cleaner handling " for larger batches ( multiple pounds ) while filling multiple ( 10's of ) salute/report cases. Once it is granulated. It still is not without risk though. It is still a hot and energetic burning composition. Should you have an accident during processing.

Usually confinement for it needs to be very good, as well as a good ignition source. It's usually not recommended for smaller reports. 

Edited October 4 by Carbon796

[DavidF]

There's a tutorial on this site with a link to a video on making and granulating this stuff, if anybody is interested. The member has now passed on, but the video is still active.

[pyrojig]

Please do share … I recently saw a members Italian shell building project using a flash coated bp granulation mix . All claims to be very hot. Even heard of members coating rice hulls with flash , or other inert materials 🧐. Binders usually a nc or shellac type , red gum alcohol bound.etc.

 Hell even guys pressing flash fueled rockets , amazing the things you can do with vitamin F 🫣

Edited October 6 by pyrojig

[DavidF]

It's here:

 

[Foguete]

On 10/1/2024 at 1:45 PM, Czx7 said:

Im looking at making some TPA flash and I was going to default to just using the diaper method as that is the a tried and true method. I was wondering if with the decrease in shock and friction sensitivity of TPA flash would it be safe to just screen the chems together or would that be unwise. If there is a quicker and more effective method that the diaper method please share. Thanks.

You can screen the chems each one separately in a 100# mesh screen to break any lumps and the mix these together by screening them together in 30# screen. Passing the mix 2-3 times by 30# screen should be enough to get the mix properly mixed.

 

 

[Carbon796]

There is no reason to be screening the needed chems for this comp. Through a 100 mesh screen. That's a lot of work for no real benefit. If you want to break up clumps in a material. You start out with a coarser mesh than you plan to mix with. 

You also shouldn't be screening a flash comp, through a 30 mesh screen. Something on the order of a 12 mesh would be more appropriate. It should mostly flow through the screen on its own. With a minimal amount of physical manipulation.

Edited October 9 by Carbon796

[Foguete]

3 hours ago, Carbon796 said:

There is no reason to be screening the needed chems for this comp. Through a 100 mesh screen. That's a lot of work for no real benefit. If you want to break up clumps in a material. You start out with a coarser mesh than you plan to mix with. 

You also shouldn't be screening a flash comp, through a 30 mesh screen. Something on the order of a 12 mesh would be more appropriate. It should mostly flow through the screen on its own. With a minimal amount of physical manipulation.

Actually when you screen the chems on 100 # is easier to integrate these together when you pass these for the 30#, this applies to any other composition, even Green mix.

Screening the F is not hazardous as long as you dont rub it with a metal tool against the mesh. In fact the powder flow easy through the mesh with no problems, just be gentle and you will be fine. 

[PyroGnome]

On 10/6/2024 at 1:42 AM, pyrojig said:

Please do share … I recently saw a members Italian shell building project using a flash coated bp granulation mix . All claims to be very hot. Even heard of members coating rice hulls with flash , or other inert materials 🧐. Binders usually a nc or shellac type , red gum alcohol bound.etc.

 Hell even guys pressing flash fueled rockets , amazing the things you can do with vitamin F 🫣

The military airburst simulator is something like 91% granulated bp coated with 9% aluminum flake, so I don't even know that the flash is strictly necessary if that's the base.  It probably acts as a fuel-air explosion with the BP just being a dispersal mechanism. 

 

[Carbon796]

Forte Nitro is a traditional granulated flash type booster, for cylinder shells.

I typically used both a granulated non traditional flash based booster. And a as screened flash based booster. The granulated booster would be blened with the 2FA canulle BP. If the as screened booster was used, it would coat the 2FA in the canulle. Just based on its fineness and the unglazed nature of 2FA. But, it wasn't applied with a binder. If an inert material was being coated with a flash based booster. It's likely it was for ball shells rather than cylinder shells. And, a binder would most likely have been used. Cylinder shells typically don't need to employ inert materials in their break charge. It's usually counter productive.

An air/fuel effect is entirely different. From boosting cylinder or ball shells for performance.

Edited October 11 by Carbon796

[Mumbles]

Use whatever screen size makes you happy to break up clumps. As an aside, I had a set of nesting stackable screens.  Passing the material through 2 or 3 progressively finer screens made quick work of breaking up clumps and mixing materials.  I never really went any finer than 60 mesh though, and never noticed any visible clumps of chemicals in my mixtures.  Your mileage may vary.  60 mesh was also the right size for me to get rid of the small amount of chunky components of parlon and red gum as an added bonus.

Carbon and I have similar thoughts on cylinder shell boosters.  I found that about 6% by weight loose powdered flash would stick to my BP burst granules.  I always used a coated flake aluminum for this mix, and I think the stearin coating helps to get it to stick somewhat.  

[PyroGnome]

Yeah I was positing it as a mechanism for the noise production of those things, I kinda went off topic there. 

Thanks for making that distinction, I knew it was more common with round shells.  Shimizu and Bleser both mention it or something like a KP mix.   I didn't have fulcanelli back then or any solid reference to cylinder shell construction and could have been doing some things better;  I spiked with dry twine for example...  I know wetting it isn't strictly necessary for pasted shells since it'll end up happening anyway but it would have been better to do it while tensioning so it would shrink even more tightly onto the shell, if that was even needed.  I usually used two strands of 10 ply running through one of those swiveling types of spiking horses made of wood that was bolted to the work table, and the amount of tension was "my arm strength + whatever weight I could add by leaning back and letting the twine hold me up", and probably going far too light on the kraft paper weight vs layer count for pasting them in, although since I was mainly making 3" shells I probably just needed add a bit of flash.  I don't know what they're breaking the consumer reloadable <2" shells with these days (except the ridiculous Mg salutes that show up labeled as star shells in multiple brands every year) but it's strong enough that I wish they were timing them to go off higher than 75 feet. 

The "loud star" shells go at least twice as high as the regular ones, amusingly. 

I found the following while looking up information about grades of NC to respond to an old question in the dragon egg flowers thread:

Quote

 

"During World War I another type of explosive used by the Germans for filling hand grenades. This was blackpowder mixed with potassium perchlorate and aluminium. The mixture consisted of:
83% of blackpowder
12% of potassium perchlorate
5% of aluminium

The presence of perchlorate and aluminum conferred high explosive properties on the mixture."

Urbański, Tadeusz. Chemistry and Technology of Explosives, vol. III, p270. Pegamon Press (1967)

 

Not completely surprising I guess given the properties of flash.  Don't use too much I guess?  🙂 Unfortunately that's about as much as they cover things, and I've not heard anyone recommend using nearly that high a percentage of flash mixed in BP or as percentage of total burst material (and this was in a grenade which is a wee bit different).  It would be nice to know what the practical cutoff is, but I guess that could be found via testing. 

[FlaMtnBkr]

I'm pretty sure I'm one of the first people in the hobby world to test TPA flash back when TPA was basically impossible to get without buying a rail car full. I tried lots of different ratios and burned some pretty big piles of it to test. It definitely makes flash safer to handle when not contained and I advocated it's use on multiple forums and even offered to ship it to people for the cost of shipping but was mostly ignored. I had a few hundred pounds of it and gave a bunch out at some of the FPAG functions which I think finally got some people interested (or at least a couple more influential ones) which was also around the time I had my first kid and didn't have the time for pyro for quite a few years.

It sounds like people are using it now and have probably documented it, but here are some of the things I found though I'll have to find and check my notes to get more exact numbers...

I didn't have a good way to test sensitivity but just lighting a pile of it made it burn like a slow star comp. I think the biggest pile I lit was either 300 or 500 grams and it still burned slowly, but most things eventually go boom once there's enough of it and I have no clue how much that is. Just the slow burning seemed to me like a good enough reason to use it.

I also didn't find the need to granulate it. It would probably make loading devices easier and could probably even make measuring by volume feasible but I never felt the extra processing was worth the extra handling that's required.

I think the formula I found worked best with most reasonable amounts of vit F was 12-17-71 (TPA - dark aluminum - KClO4)

Higher percentages of TPA could be used with larger amounts like multiple pound bottom shots assuming the time fuse/spolette was cross matched etc to get extra flame and heat. I didn't go very high with the TPA percentage because I didn't use large amounts. 

With the above ratio I found under around 5 grams needed something to add heat to make it reliable. It could be a couple pieces of black match long enough to be close to the fuse, BP granules added in, or cutting the fuse at 45 deg and dipping into a flammable slurry. More than 5 grams using my chemicals would light with just visco or time fuse assuming there was decent confinement (basically anything more than a triangle cracker). But it also can't hurt to add something to get the temps up the first few times while you get a feel for it, if it's a salute with only flash so you don't have to worry about reliability.

I lit the same devices side by side multiple times with the only difference being 1 was regular flash and the other TPA flash, and most people seemed to agree that it was either louder or had a deeper tone so it sounded louder. In small salutes (2" or 3" ball) I found I could use 10-20% less and it sound the same.

Since TPA is basically plastic, I found some of the bags I was able to get of it had water in it. Not sure if it got wet or if absorbed water from the air or never got dried properly after production? But I got in the habit of putting a new bag in the sun for 20 or 30 min to see if any condensation formed. Hopefully there are better supplies of it now but it can't hurt to check.

I may have forgot some things but I tested a bunch with it before I started suggesting it's use so if anyone has any questions I might be able to answer? I also got some blue aluminum when it first started showing up and I found I preferred the TPA flash, at least for smaller hobby size amounts. I found the blue aluminum difficult to impossible to ignite unless you were using large amounts or cut it with dark aluminum to make it easier to light.

Anyways, I only check in every so often and haven't seen TPA mentioned much so thought I'd put my 2 cents in, though surely is getting closer to a quarter the way prices keep going up...

Someone also mentioned adding flash to BP to get more noise I think? That's one possibility but another is just adding some aluminum to coat the BP granules. The aluminum increases the heat which increases the pressure in a fixed volume (ideal gas law) as well as increases the burn rate of the BP which makes the now higher pressure spike quicker and get even higher before the shell starts to fracture and come apart. Basically, a little aluminum was a trick to get more power and noise from a BP burst without having to mess with flash. Might be worth a try...

Edited October 24 by FlaMtnBkr
Typo

[pyrojig]

Excellent description. Couldn’t have said it any better. I have found the same results both mix’s . Hot ignition is key. Also if you had a cheap source for tpa that cuts costs way down vs lg amounts of al. Not sure if the boom was deeper , more of a crack sharp like antimony mix

[Carbon796]

Iirc, I read a mil-spec paper/document once. That was comparing TPA based flash compounds. To other more conventional AL based flash compounds. The TPA based flash compound, developeds a higher "pressure signature" than a standard 70:30. As far as sound quality is concerned. TPA based reports or BS's sound excellent to my ears.

One trait of TPA based flash that I didn't really care for, for overall use. Was the reduction in light output. But creatively, that does give you an added "tool" to work with.

I don't know about current pricing. Back when I bought a 50# bucket of it. It was a little over $2 a pound iirc. So it can definitely cheapen the comp up some.

10# will definitely go boom. In an open 5gal bucket. I used to prefer to process star comps, in 5gal buckets. Anywhere from 10 to 30# at a time/color/effect. So I was curious if TPA flash,  processed in a similar manner. Was really as safe as processing/working with star/BP based comp's. As I had previously read from others. It was not  . . .

 

Edited October 26 by Carbon796

[FlaMtnBkr]

I figured at a certain point if there was enough of it there would be a boom. But I'm pretty sure 10# of any pyro comp going up is something you wouldn't want to be close to. I'm sure many know, but even a few packs of sparklers bundled together can be pretty devastating...

For the people that have used it, did you use it as a powder or go thru the process of granulating it with NC? I'd also be curious if anyone ever did any sensitivity testing to see if it reduced friction/impact/static sensitivity or just slowed down the burn rate when unconfined (in amounts smaller than 10#