Coating Rice Hulls

[pyronoob]

i'm having some problems with coating rice hulls either in mill dust bp with +2 dex or with KP burst powder...i'm trying to coat 7:1 however i'm only getting about half of the powder to stick and the hulls are not that nice and crisp.....what am i doing wrong??

[OldMarine]

How are you preparing your hulls?

[pyronoob]

im soaking them in hot water for a minimum of 10 mins...using an old pillow case, draining the water and slinging the rest off just like the article on FW says to do.....put them in a 5 gallon bucket and then adding the mill dust

[NeighborJ]

I've had the same problem with that method. In the end I threw them all in the star roller and added the bp with spritzing water. I will follow this thread to see how everyone else does it.

[OldMarine]

pryonoob, like NeighborJ said, just spritz in some more water until all the powder is picked up. Be sparse with the water to avoid clumping. I put a lid on my bucket and shake the snot out of it between spritzes.

[pyronoob]

Okay...I've screened out the powder and have tried to salvage what i have already....OM...i put it back in my bucket and have been shaken and stiring the crap out of it....we'll see how it works....just in case i've made a batch of BP with +5 dex

[Mumbles]

Everything sounds about normal so far. Just wetting and soaking the hulls will not usually provide enough moisture for all the BP or KP to stick. After the initially coated hulls have basically taken up all they can you will need to start spritzing and stirring/tumbling. A star roller makes this process the easiest, but shaking or stirring by hand also will work just fine.

 

I tend to keep the hulls on the damper side when I'm doing this personally. I like the damp hulls to pick up the comp as opposed to having dry hulls tumbling around in loose powder and spritzing on top. I feel this provides less dust and unbound comp as well as providing a denser more well adhered coating, but that's mostly anecdotal. That's of course just one point of view, figure out what works for you.

[DavidF]

I actually boil my hulls in water, and I leave them on low heat until they all sink. 10 minutes is not long enough. I do mine in a bucket too, with a lid on it. I break up the clumps partway through by screening through a 4 mesh (or so) sieve. To get 7:1 to all stick is a tall order. Extra spritzing is needed, at least for mine. I use 5% dextrin.

[braddsn]

I first take my dry hulls, and screen all of the fine stuff out of them. If you don't do this, some of your bp will stick to these little bits and it will appear like your bp didn't stick to the hulls. After I screen all the fines out, I put the hulls in a pillowcase, then drop them in a 5 gallon bucket of water. I let em soak for 5 minutes or so, then spin the pillowcase until most of the excess water is out. I use a 5:1 bp:hulls ratio. I pour some hulls in another 5 gallon bucket (that has a lid). then pour some bp in, then hulls again, then bp, in layers until all of my hulls and bp are in the bucket. Then I snap the lid on, and shake, rattle, and roll!! I shake it, roll it on the floor, etc for a good 5 minutes vigorously. Then I open the lid, pour the hulls out onto a big screen to dry, and I am done. I suggest trying 5:1 instead of 7:1. I used to use 7:1, then I switched to 5:1 and they perform exactly the same, and seem easier to make. Hope this helps.

[ExplosiveCoek]

If you have a star roller:

 

Roughly 200 g rice hull's, one cup of water, dump in the water and let it spin. It will stick together.

At this point make sure everything has been whetted properly. Add the bp whilst breaking up any lumps that form, and you'll get nice coated hull's.

 

I always had the issue of hull's that were too damp after soaking, but then again, I never removed the excess of water thoroughly.

[pyrokid]

The way I've always done it is to soak the hulls in room temperature water and then drain them, and separate the powder into 5 increments. The first four contain binder, and the last one doesn't. The goal of this is to prevent the finished hulls from sticking to each other. I like the sound of the star roller method, but I don't do enough volume to make it worthwhile, and I think it would be challenging to get the right water content in the hulls at the beginning, unless you start that process by soaking them as well.

[NeighborJ]

If you ask a hundred pyros how to coat hulls, you will receive a hundred different answers. Like what Mumbles said at the beginning of the thread, just find what works for you. The only requirements are that it be fast and lighter then granulated bp. If you meet those, then you are doing it right.

[OldMarine]

I use hot water, soak the hulls (after screening fines) about 15 minutes and then sling them in a pillowcase to remove excess water. Then I proceed exactly as pyrokid outlined above. I use my hand and a bucket rather than a roller since I have neither a roller nor a mill that would produce enough powder in a reasonable time to use a roller....YET!

[braddsn]

Something to add.... I used to make them in my star roller. To be honest, it was messy... dust everywhere, and took a while. Find a 5 gallon bucket with a lid and do it the way I posted above. NO MESS!!! And, it takes waaaaaay less time. With this method, I am done with the entire process in 15 minutes.

[pyronoob]

Thanks for all of the advice!! I increased my dex to +5 and dropped the ratio to 5:1. i hand mixed it in a five gallon bucket and this worked niicely.

[dagabu]

I actually boil my hulls in water, and I leave them on low heat until they all sink. 10 minutes is not long enough. I do mine in a bucket too, with a lid on it. I break up the clumps partway through by screening through a 4 mesh (or so) sieve. To get 7:1 to all stick is a tall order. Extra spritzing is needed, at least for mine. I use 5% dextrin.

 

Ditto for me, I don't run them through the 4 mesh though, I just use my hands. I do find that I do get all the comp to stick except for the last few ounces (I do 1000g of dry rice hulls to 7.5 kilos of BP) but that just gets collected on the drying screen and gets reused.

[starxplor]

I have made two small batches of coated hulls so far, both 20g hulls, 100g powder for 5:1 ratio. I screened the hulls first, dumped them in a bowl with water poured from my kettle(just sub-boiling), and left them for about 15 minutes. I put the hulls in a covered bowl add some of the powder, and shake/roll for a while, repeating until all the powder is in use. After spreading to dry, I shake them with a screen to get just the covered hulls.

 

Now, after all this is my question: What is left appears to be mostly powder, in little balls like on an old sweater, and a few thin bits of hull with no powder. Can I add this to my next batch or do I have to break up these bits and try to get the hull slivers out before I can use the powder on more hulls?

[OldMarine]

Are you slinging the water out of the hulls after soaking? Also don't add your powder all at once, add it in batches so you can adjust the actual amount rolling around in there at a given time. I usually get about 2/3 of the way through and have to spritz a bit of water in my hulls to get them to pickup the remainder of the powder.

[starxplor]

Yes, slung around to remove excess water. As mentioned above, I added powder in bits. I also had to spray a bit of water with a normal water pray bottle on finest setting for even distribution for the last bit of powder. Once I could see some of the last application was still rolling around with the hulls, I started spraying.

 

I am wondering if it is that spraying with some powder on the bottom of the bowl that cause the little balls to bind up.

[OldMarine]

It sounds as if you didn't screen the hulls well enough and left too many splinters which grabbed up the BP and started forming little cores.

[starxplor]

I used a kitchen screener, the kind with a rubberized rim and handle, so if anything, I would expect to let too much through when screening.

 

The 'little balls" I mention are small enough to pass through the same screen, so if they built up on something else, I would expect that core material to have made it through the screen in the first place.

[Mumbles]

It's a little hard to say where they came from. You can certainly add the powdery mix back to the next batch of hulls however. They'll soften and stick. If you're at all concerned, add it with the first batch of powder while the hulls are good and wet. It'd be equally fine to add it into blackmatch slurry, BP to granulate, or something similar as well.

 

Another application I use it for is the final BP coat on stars or whatever. I like the slightly coarser texture on the outside surface to help take fire. I save up the excess from coating hulls, priming stars, etc. for this purpose. I tend to keep the fines from making BP or polverone separate, and use that for some other applications however.

[starxplor]

I like the idea to use as priming, think I will label a new container for this use. Thanks.

[Richtee]

Something I never done. Just got a pound of hulls for grins.

 

What’s the phenom anyway? It acts like quickmatch kinda?

 

On Edit: I mean it’s rapid flame front/deflag. Like my quickmatch tubes sound like a 1911 forty five

Edited February 4, 2022 by Richtee

[SharkWhisperer]

Something I never done. Just got a pound of hulls for grins.

 

What’s the phenom anyway? It acts like quickmatch kinda?

 

On Edit: I mean it’s rapid flame front/deflag. Like my quickmatch tubes sound like a 1911 forty five

Conserves BP when you don't need the full shell void charged with granular powder to get desired spread. Also provides additional airspace voids (both between hulls and within hulls) that allows more gas expansion before burst pressure is achieved. In some shell sizes, if the burst:star volume ratio is too large, you'll still have burst charge burning when the shell ruptures, which is pretty much wasted energy and light production that you may or may not want.