13 replies to this topic

[NorCalPyro]

I have been using a 70/30 whistle mix made by diapering as a booster for burst on spherical shells and it has worked well for me. At the Western Pyro Association Winter Blast I saw a lot of folks using flash as a booster and claiming it is "safer" than whistle for building spherical shells. The comment was that Whistle is more friction and shock sensitive than flash and hence flash is "safer". Their thought is that the closing of the shell inherently has frictional grinding of the whistle between the rice hulls and also potentially an impulse to the whistle from taping on the shell to settle the contents in order to help close the shell.

I would appreciate hearing what folks are using and why.

[MMMMMM Pyro]

Now thats a tough one,

Personally, flash because for me I feel it provides a better break.

With regards to Whistle being more sensitive however... I think it depends very much on the formula, Salicylate or benzoate? Fe2O3 or CuOCl (for example)?

[YT2095]

BP slurry coated Rice or Wheat chaff / husks would be my choice, I don`t trust either composition really.

but I speak as a Chemist rather than a Pyro.

[BrightStar]

Granulated benozate/perc whistle is certainly easier to ignite than perc/dark al flash so your friends may well have a point. Whistle can however be desensitised to friction by granulating with vaseline and it works just as well. As far as I can see, the main reasons why whistle is often said to be 'safer' are that it may be prepared in a wet state (unlike flash) and will only self confine in large quantities.

If you image closing a small shell, it is not yet glued or pasted and so would not burst in the conventional manner. In case of an accident at this stage, a flash boosted burst might lead to more of a hazard than slow burning unconfined whistle. On the other hand, I could see myself preferring to use a small quantity of 70/30 flash (hopefully mixed by someone else) in big shells for the purported lower friction sensitivity. With the larger shells an accident would probably be equally serious either way.

One trend I have seen from across the pond for 6" ball shells is to dust the BP burst with slow nitrate flash (KNO3, S, Bright flake Al) before use. This is apparently a good booster but is it safer? Does anyone know?

Edited by BrightStar, 20 February 2008 - 07:13 PM.

[YT2095]

it still needs stabilising, Boric acid is the Usual "fix".

I have no idea as to longevity in way of shelf-life however, I don`t like metal oxidizer mixes fullstop anyway.

[Pretty green flames]

The probability of an accidental ignition of the booster, be it flash of whistle, can be greatly reduced by the use of a flash bag, as this prevents Booster/Rice hulls contact which can cause friction during the handling of the shell, it also prevents the booster getting "lost" in the shell as it keeps it all close together thus a smaller amount might be needed to get a similar effect as with no flash bag.

I personally use Perch flash reduced with KNO3 to make it a bit more forgiving.

[dr thrust]

sorry to ask its properly on the forum somewhere what material are you using as a flash bag?

[starseeker]

sorry to ask its properly on the forum somewhere what material are you using as a flash bag?

For a round shell i would use some tissue paper for the flash bag {not loo paper }and for a can shell i would use a couple of turns of 70lb craft paper,
regards.

[Frozentech]

I have been using a 70/30 whistle mix made by diapering as a booster for burst on spherical shells and it has worked well for me. At the Western Pyro Association Winter Blast I saw a lot of folks using flash as a booster and claiming it is "safer" than whistle for building spherical shells. The comment was that Whistle is more friction and shock sensitive than flash and hence flash is "safer". Their thought is that the closing of the shell inherently has frictional grinding of the whistle between the rice hulls and also potentially an impulse to the whistle from taping on the shell to settle the contents in order to help close the shell.

I would appreciate hearing what folks are using and why.

When I use flash in round shells, it's in a coupette ( flash bag - either a "bubble" of saran wrap, or paper tube such as coin wrapper or 2 turns of 30lb kraft ), which isolates it from friction during loading/closing of the shell.

With whistle, I usually dump a few grams at the center of the shell, I never really gave it much thought as to the sensitivity of whistle, I dust whistle on KP/rice hulls for burst in cylindrical shells all the time though, have not used flash as a booster in those... I guess a few sensitivity comparison tests are in order.

[BigG]

Now thats a tough one,

Personally, flash because for me I feel it provides a better break.

With regards to Whistle being more sensitive however... I think it depends very much on the formula, Salicylate or benzoate? Fe2O3 or CuOCl (for example)?

I'll be very intrested to see where they got thier information. Any reasearch I read suggest that flash is more sensetive then whistle, and whistle comp has a much smaller record of accidents on sites that process both. The law - backed by wide reseach put seavere limit of flash becuase of those issues (in europe, no one device can have more then six gram of flash) - such issues do not exists with Whistel comp.

I do not use flash AT ALL.

[NorCalPyro]

Great discussion and comments! I am using perc and salicylate diapered for mine. One of the more experienced shell builders I spoke with liked a granulated whistle made with Vaseline. For those using a flash bag, have you noticed any change in the break performance of your shells as opposed to having the booster loose in the BP hulls?

[MDH]

Whistle is better for bigger shells. Flash for smaller ones.

[pyrotrev]

A lot of Chinese shells seem to use just a little flash dusted all over the break charge. You don't seem to get much of a flash when it goes off, so I assume the benefit is to spread fire throughout the burst charge more quickly.

[MDH]

I know that some companies do use a small portion of aluminum dust and a strong oxidizer over their lift when they run low of lift powder...