First post--a couple questions about various large firecrackers. Why are the cases only about half full?

[JohnWI]

Hello folks, first post on this forum.

I'm a chemist by training, but have had a lifelong interest in pyro.  That said, I have never manufactured any (in the name of safety and legality).  I'm trying to brush up on some legalities and ordered a couple of books on the subject.   So, that said, my questions here are purely academic.  I have never, and will not until I legally can, produced any pyro devices.

My question are regarding larger firecrackers of the M-80 or cherry bomb sized devices (which were commonly, although illegally available during my youth).  It seems that they were maybe 1/2 full of flash powder.  I tried doing a little research, and am wondering if their was an actual reason for that (ie, the dead air space, for whatever reason, made the devices louder)? or if it was some kind of marketing ploy--ie, a bigger tube implied a more powerful device, whether it was true or not.

Another was with the use of sulfur in flash compositions.  Several sources claimed it made for a more vigorous, louder report, while others claimed the addition of sulfur did little more than destablize the composition and make it more sensitive--perhaps dangerously so.   Can anyone vouch for whether sulfur is or is not a good component of flashpower (perch./aluminum powder).

 

Thanks!  Again, these are academic questions.  I have no intention of building any of these devices.  Certainly not until I'm confident about the rules and safety issues.

 

[Arthur]

There is, in professional manufacture, a constant demand to minimise cost, so leaving an air space inside MAY simply be a cost reduction measure. Maybe there is also something to do with flame propagation through a packed solid vs propagation through a dust cloud in the microseconds between ignition and the case  bursting.

If you are in the USA there are several pyro clubs that hold licensed making events in the summer/autumn. 

[All10Fingers]

I believe the cards were half empty, not because of the dead space inside. But because of the increased surface area of the casing creates a bigger sound. So it's not about having empty space. It's about Maximizing the decibels produced from a certain amount of powder

[Richtee]

Well, this is from an archive I have- of flash formulations of all sorts. Your sulfur is mentioned and called out by a master: And, on edit, the space left does indeed contribute to the bang, allowing better flame front propagation and pressure build-up in the casing.

 

 

Edited May 26 by Richtee

[countryboy7978]

Empty space was not there to increase sound. Plain and simple, more report composition equals a louder report. The original factory made salutes were tumble mixed. This was especially true of the cherry salutes and torpedos. The components were loaded into the casings unmixed, especially since many of them used potassium chlorate as the oxidizer along with sulfur and or antimony sulfide. They needed the space in the casing to mix. Even the cylinder type salutes were tumble mixed with a saw dust buffer. Later on they used premixed composition especially when perchlorate became more common. The composition was added using jig boards for some of these that dispensed a premeasured amount of composition. 
 

Flash composition settles very rapidly so the space increases as they are handled. 

[Mumbles]

If you want to get more involved, there is a state club that meets about an hour and a half from you.  I used to be a member until I moved away, and cannot recommend it enough.  Fabulous people.  

[Richtee]

On 5/29/2024 at 12:16 AM, countryboy7978 said:

Empty space was not there to increase sound. Plain and simple, more report composition equals a louder report.

I would bet it would. But for EQUAL amount of comp and varying only casing size I’d also bet a larger casing would be louder, holding all else constant.

 

That I think was the question. Or what I gleaned from the OP.

Edited May 31 by Richtee

[pyrojig]

Everything (as mentioned )in manufacturing comes down to cost . 

While more flash (full tube ), vs standard (1/2 full) is almost indistinguishable in decibels. So there is a huge savings as a manufacturer to do this approach.  Cherrys and other 2 cup crackers are virtually impossible to get more than half volume when assembling. 
There are some really great replies above giving insight