BP coated rice hulls, Why?

[MWJ]

I was just wondering why use bp coated rice hulls instead of just bp? Is it to soften the bust to not get a blind burst? Or is it so you don't use so much bp?

 

I'm working on my first 3" shell and need to know the ratio of bp and rice hulls. I read here that for a 3" shell to use 5g bp (meal powder) to 1g rice hulls. Is this right?

 

Thanks guys,

Mike

[nater]

Usually hulls are coated between 4:1 and 7:1 meal to hulls, so your ratio is in the ball park. Coated hulls are used to keep the proper amount of BP without getting too heavy. Imagine how heavy a 12" shell would be if it were filled with granulated BP. Coated hulls also help the flame propagate through the burst Edited February 28, 2014 by nater

[MWJ]

That makes sense. Thanks. I check our local feed store for rice hulls and they sell it for $32.00 for 25 lbs.

Thanks again Nater

[bob]

Sorry about this post, by the time I was finished writing Nater had posted and he did a much better job at explaining it then I did.

bob

Edited February 28, 2014 by bob

[nater]

Other things can be coated with BP as well. Rice Crispy cereal, grass seed, cotton seed, bits of cork and other things as carriers. On Passfire, Kyle has a tutorial for a puffed grain he likes to coat for burst on small shells.

 

Ned uses his coated rice hulls for lift, so burst is not the only possible use.

[pyrodoc]

Even, i used to get puzzled by rice hulls..

 

One more ques: Sometimes the use flash powder also as a burst charge.

Is it to give more burst power?

[nater]

Yes. Small amounts of flash or whistle can be gently coated on the BP hulls as a final layer or a small amount can be sprinkled on top before the shell is closed or pasted.

 

Slow flash made from KNO3 is often used. I like whistle since I usually have some ready for rockets. Just be careful with boosters on your burst. It is easy to blow shells blind and the white spot from flash can be distracting.

[MWJ]

Other things can be coated with BP as well. Rice Crispy cereal, grass seed, cotton seed, bits of cork and other things as carriers. On Passfire, Kyle has a tutorial for a puffed grain he likes to coat for burst on small shells.

 

Ned uses his coated rice hulls for lift, so burst is not the only possible use.

What would be better to use for burst? as far as rice hulls or any of these.

[Maserface]

What would be better to use for burst? as far as rice hulls or any of these.

Rice hulls, unless you cant get them.

 

Cotton seed is common larger shells, for everything else, rice hulls

[nater]

I have only used rice hulls myself.

[ddewees]

This stuff is great, get the 3/8 size.

 

http://www.marylandcork.com/Granulated-Cork.aspx

[bob]

I personally use grass seed. I have been told that grass seed works better than rice hulls because grass seeds are shaped like well seeds so the seed will get an even coating of black powder, where as rice hulls are shaped like little canoes, so the hollow spot on the hull gets an unproportionatly high amount of black powder, this pocket of black powder on the rice hull takes longer to burn then the coating on the outside of the hull. Another thing is grass seeds are smaller so if you are making small shells (under 5 inch I believe) grass seed will work better.

bob

[pyrodoc]

Yes. Small amounts of flash or whistle can be gently coated on the BP hulls as a final layer or a small amount can be sprinkled on top before the shell is closed or pasted.

 

Slow flash made from KNO3 is often used. I like whistle since I usually have some ready for rockets. Just be careful with boosters on your burst. It is easy to blow shells blind and the white spot from flash can be distracting.

I have dissected one big 6 inch shell. (It was damp as it had fallen in water, i could never see any fire from spollete after firing).

 

But, it contained a huge amount of flash. It was sprinkled all over rice hulls as well as every damn star was coated with it). Infact, i was kinda shocked to see the amount of flash inside it.

May the companies here practice something different. Yesterday was talking to a local pyro from here and he told me that they use flash frequently in shells as it acts as a good prime, and also keeps the large comets in place as it fills up all the empty space.

[nater]

Chinese shells, especially small ones, often do have a large amount of flash. You can tell by the white spots burning your retinas when they break and the large sloppy bursts. However they prime their stars, it seems to work. Using the formulas common to hobby builders, you are not likely to have those same results.

[Peret]

Another advantage of coated rice hulls is they're somewhat crushable, so you can overfill your shell and still get it closed. I'm not sure you'd have that same property with coated cork, corn cob or grass seed.

 

As for why rice hulls, one word - Shimizu. Rice hulls are obviously plentiful and cheap in Japan. In wheat growing countries, not so much, so you find instructions to fill "Italian" shells with polverone (roughly screened gunpowder). Polverone is heavier and considerably more expensive in materials and doesn't appear to give you any better burst, but it fills small gaps better and Italian shells probably need that for rigidity. In my opinion, it's mostly wasted except for the central canule.

[pyrokid]

Ddewees, could you please elaborate a bit on your experiences with granulated cork?

 

Did you try different sizes? How laborious is the coating process?

 

I'm looking for a way to cut down on my polvorone use in can shells.

[BrainDamage]

will any grass seed work

[bob]

I would think that any seed that is in the size and weight range we need it to be in should work.

bob

[ddewees]

Ddewees, could you please elaborate a bit on your experiences with granulated cork?

 

Did you try different sizes? How laborious is the coating process?

 

I'm looking for a way to cut down on my polvorone use in can shells.

The biggest advantage is it consolidates so well. You soak it and coat it as you would rice hulls... I've only heard of people using the 3/8 size.

[Arthur]

BP as filler uses a LOT of powder which costs and weighs a lot, so it's best avoided. As shells get bigger they need proportionately less burst, so while a 2" shell may need BP for break a 4 - 10" will not. using rice hulls is good if they are cheap -remember that most fireworks are made down to price not up to quality! Hulls will compress as the hemis close so hold the ingredients in the right place, likewise a few plain rice krispies will crush under closing force. Part of the objective is to form a spaced matrix of powder so that the flame front propagates as rapidly as possible -which is why some people roll stars of burst onto krispies as cores.

[enanthate]

Just to add my 2 cents from testing 2 different materials; Original rice hulls seems to be the quickest mix. I was using cereal (damped and let dry puffs, becoming rock hard at the size of normal rice), and the rice hulls poofed a bit quicker (noticeable by eye).

 

A bit offtopic: Is over-milling my BP good or bad? After thinking about it, the quicker it is it generates less heat I assume. The faster BP the better prime is needed? Perhaps it doesn't really matter?

[marks265]

Just to add my 2 cents from testing 2 different materials; Original rice hulls seems to be the quickest mix. I was using cereal (damped and let dry puffs, becoming rock hard at the size of normal rice), and the rice hulls poofed a bit quicker (noticeable by eye).

 

A bit offtopic: Is over-milling my BP good or bad? After thinking about it, the quicker it is it generates less heat I assume. The faster BP the better prime is needed? Perhaps it doesn't really matter?

 

Really, and in the grand scheme of things, all you want to do is be consistent. There are 3 important variables that control what we do, time, money, and the materials that we have readily available to us. Next we have artistic variables such as varying the chemistry and/or the "3 important" variables that I suggested above. As far as over milling goes, you may find you can use a little less because you had more time. In the end the testing of your handy work will tell you what your next move might be. A "poof" on the ground really means nothing, compared to an actual test to put something skyward or outward such as lift and break, respectively of course.

 

When you used cereal and hulls you changed the grain size and structure. These types of things matter when you're loading a shell because of how much powder you actually put in a shell. You may have had more or less air space in the completed shell or had a different characteristic to the flame propagation through the shell. If packed to tightly you may have a fire block for part of the shell and a section of stars may not light. Where black powder carriers won't matter is when setting them on fire on the ground and in the open.

 

 

Mark

[Mumbles]

I'm always sort of torn on the idea of using a filler in cylinder shells. I guess it would make sense if you were still paying $5/lb for potassium nitrate. When you start to get into making cylinder shells, especially big ones where the costs add up, typically you'd begin to buy in bulk. Even with rising bulk prices, you're still looking at less than $1.50/lb for polverone. I do feel that the polverone plays a non-zero part in the proper burst of a shell. Given that burst space is already limited in a cylinder shell, I don't know that I'd want to go reducing the active component significantly.

 

To be a good substitute for straight polverone, you'd want something non-compressible. For it to make any sense, you'd need something with suitable physical properties that was cheaper than polverone on a volume basis. Even for something that might work, like ground corn cob, you're still possibly spending more money. I can't find a good reliable bulk density to get any sort of good idea though.

[enanthate]

Cheers, Mark. What you're saying sure makes sense. Will keep experimenting until I find my own way.

 

Mumbles, the prices you are mentioning are ridiculous! You guys are lucky to stay in America. I'm easily paying $20/kg KNO3..

[nater]

I just made a few pounds of polverone and I don't really think of the cost of anything I make. I have KNO3 that was purchased for $1/lb. Sulfur, commercial airfloat charcoal and dextrin are all inexpensive too. I'm guessing the finished product is around $1 - $1.50 / lb. Not too bad, I don't think. I don't build the large shells, so what I use goes far. 6" cylinders are the biggest thing I have planned for this season and for a while, you can always add more breaks for something more impressive once the construction techniques are down.