Coating rice hulls most efficiently?

[AdmiralDonSnider]

On my way to the first spheres I´ve recently attempted to coat rice hulls with H3. I followed the steps given in Dave Blesers book (Round stars and Shells), including soaking the hulls in warm water for about half an hour, letting them drain on a screen for 15 mins and applying the powdered H3 by shaking/swinging it together with the damp hulls in a container.

 

Bleser suggests to add the H3 in two increments. Doing so, the hulls seemed to take up the first portion well, but unfortunately most of the second increment came out still separate, in powder form or slightly clumped, but not on hulls. So my result is a mix of coated hulls and H3 in powder form, more or less granular.

 

The outcome burns really fast, but: As you want to know the exact ratio hulls:break for optimum results, I guess this is bad news as the hulls now carry a lot less than expected.

 

I used 2 add% of rice starch (as suggested by Shimizu), in contrast to the 5% dextrin suggested by Bleser. Maybe not enough binder?

Or did I allow the hulls to get drier than desired?

Don´t know what went wrong...

 

How do I efficiently coat stuff like hulls to make sure that 100% of the powdered material will adhere? How do you usually do that? Do I have to wait for my star roller?

 

Thanks folks!

[jrin0630]

On my way to the first spheres I´ve recently attempted to coat rice hulls with H3. I followed the steps given in Dave Blesers book (Round stars and Shells), including soaking the hulls in warm water for about half an hour, letting them drain on a screen for 15 mins and applying the powdered H3 by shaking/swinging it together with the damp hulls in a container.

 

Bleser suggests to add the H3 in two increments. Doing so, the hulls seemed to take up the first portion well, but unfortunately most of the second increment came out still separate, in powder form or slightly clumped, but not on hulls. So my result is a mix of coated hulls and H3 in powder form, more or less granular.

 

The outcome burns really fast, but: As you want to know the exact ratio hulls:break for optimum results, I guess this is bad news as the hulls now carry a lot less than expected.

 

I used 2 add% of rice starch (as suggested by Shimizu), in contrast to the 5% dextrin suggested by Bleser. Maybe not enough binder?

Or did I allow the hulls to get drier than desired?

Don´t know what went wrong...

 

How do I efficiently coat stuff like hulls to make sure that 100% of the powdered material will adhere? How do you usually do that? Do I have to wait for my star roller?

 

Thanks folks!

 

I have had the best results when I have wet the hulls in hot water and then, using a microwave save bowl, cook them until the water boils. Let them soak for 20 min and you will notice they all fall to the bottom of the water when they are fully soaked. They I put them in a screen pouch for 20 seconds on the spin cycle of the washer, so they come out damp and clumpy before coating them. That seems to be the right amout of moisture. That's it. Using that method and 5% Dextrin, I'm getting a really good coating. I'd say 95% plus.

[Swede]

You can simulate the washing machine's spin cycle with a cheap alternative... buy one of those mesh laundry sacks used for socks and such, the type with a really fine mesh that will contain the hulls. After heating and/or soaking, load the sack, attach a nylon rope, and start whirling it about your head in a circle, like an old-time sling. Maybe 2 meters seems to be a good length. This does work to get rid of excess water very quickly.

 

In my limited experience, I get better adhesion with damper hulls. They take longer to dry, but there is enough moisture to activate the binder during the second or third coating, and of course there is nothing stopping you from using a spray bottle to moisten the mass a bit if it becomes too dry.

[jrin0630]

You can simulate the washing machine's spin cycle with a cheap alternative... buy one of those mesh laundry sacks used for socks and such, the type with a really fine mesh that will contain the hulls. After heating and/or soaking, load the sack, attach a nylon rope, and start whirling it about your head in a circle, like an old-time sling. Maybe 2 meters seems to be a good length. This does work to get rid of excess water very quickly.

 

In my limited experience, I get better adhesion with damper hulls. They take longer to dry, but there is enough moisture to activate the binder during the second or third coating, and of course there is nothing stopping you from using a spray bottle to moisten the mass a bit if it becomes too dry.

 

I like the washing machine alternative....I'll try that. And I agree on getting better adhesion with damper hulls. Unless they are in boiling water long enough to sink to the bottom of the bowl, they're not wet enough and you won't get the best adhesion.

[Mumbles]

I suspect your problem has to do with impatience and not technique. You have to allow the water from the hulls to soak through the H3 layer in order to force the outer layer to adhere. This is where the star roller really comes into it's own. I make around 1000g burst comp at once, and then whatever the appropriate amount of media is. I do the coating in a 5 gallon bucket. I add the composition in 4 or 5 parts. I sort of simulate the star roller by constantly stirring the whole mixture with my hand. The hulls don't really start to break up until the 3rd increment or so. I occasionally have to wet the hulls a little. It really does take a while for the water to soak through.

 

Perhaps allow the hulls to sit in the container for about 10-15 minutes between additions to allow the water to diffuse. Then another 10-15 minutes after the second addition. Give another shake/stir before pouring the hulls out to dry. This might do the trick.

[AdmiralDonSnider]

I have had the best results when I have wet the hulls in hot water and then, using a microwave save bowl, cook them until the water boils. Let them soak for 20 min and you will notice they all fall to the bottom of the water when they are fully soaked.

 

Is it vital that they fall to the bottom?

 

You can simulate the washing machine's spin cycle with a cheap alternative... buy one of those mesh laundry sacks used for socks and such, the type with a really fine mesh that will contain the hulls. After heating and/or soaking, load the sack, attach a nylon rope, and start whirling it about your head in a circle, like an old-time sling. Maybe 2 meters seems to be a good length. This does work to get rid of excess water very quickly.

 

I also heard of a pantyhose being used and whirled.

 

I suspect your problem has to do with impatience and not technique. You have to allow the water from the hulls to soak through the H3 layer in order to force the outer layer to adhere. This is where the star roller really comes into it's own. I make around 1000g burst comp at once, and then whatever the appropriate amount of media is. I do the coating in a 5 gallon bucket. I add the composition in 4 or 5 parts. I sort of simulate the star roller by constantly stirring the whole mixture with my hand. The hulls don't really start to break up until the 3rd increment or so. I occasionally have to wet the hulls a little. It really does take a while for the water to soak through.

 

Perhaps allow the hulls to sit in the container for about 10-15 minutes between additions to allow the water to diffuse. Then another 10-15 minutes after the second addition. Give another shake/stir before pouring the hulls out to dry. This might do the trick.

 

That sounds reasonable. Bleser seems to be a bit too vague in his description of the process; anyway, he does not mention the necessity of rests between the coating steps (to allow the water to diffuse). I´ll definately give it a try. Thanks!

 

Other than that, could you briefly describe the coating by rolling machine? Does it work like growing stars, with a spray bottle, or does it employ soaked hulls also?

[jrin0630]

Yes, when the rice hulls fall to the bottom of the bowl, that signifys they are fully saturated. That full saturation seems to play a roll in the adhesion. They will fall to the bottom within a few minutes of the water boiling in the microwave. In the past, I only let them soak in hot water, without falling to the bottom, and I got maybe 60% adhesion at best. And all I did was adjust the soaking of the hulls, nothing else.

[Mumbles]

I would second the concept of letting them, or at least most of them fall to the bottom.

 

I don't know if the resting between coatings is necessary or not, but it make sense to me conceptually. I've experienced the delay between coating and the outside becoming wet enough to take up more powder. When you "hand roll" as I do, you will see dry or slightly damp powder left behind slowly being taken up.

 

Every time I see hulls being coated in a star roller, they start with dry hulls. They are sprayed with water while tumbling until they hulls just start to stick together. Stirring by hand is frequent to remove hulls stuck to the roller and help to circulate the hulls to prevent the top from becoming saturated, while the bottom remains dry. Then just start dumping on powder. Stir with your hand to break up clumps, and knock powder from the wall of the roller. Alternate spraying and dumping on powder until you're almost done. At the end dump a bunch of powder on the hulls and let it rotate on it's own for 10-15 minutes. This lets the internal water wick out and doesn't let them end up overly wet. This is actually where I got the resting idea I suggested above from.

 

Another trick I sometimes see is to add the final 1/2 to 1 part without any sort of binder. I've taken to doing this, and it acts like flour with baking. The hulls almost can't stick together. The final hulls are sometimes a bit dusty, but quite free flowing.

[dagabu]

I would second the concept of letting them, or at least most of them fall to the bottom.

 

I don't know if the resting between coatings is necessary or not, but it make sense to me conceptually. I've experienced the delay between coating and the outside becoming wet enough to take up more powder. When you "hand roll" as I do, you will see dry or slightly damp powder left behind slowly being taken up.

 

Every time I see hulls being coated in a star roller, they start with dry hulls. They are sprayed with water while tumbling until they hulls just start to stick together. Stirring by hand is frequent to remove hulls stuck to the roller and help to circulate the hulls to prevent the top from becoming saturated, while the bottom remains dry. Then just start dumping on powder. Stir with your hand to break up clumps, and knock powder from the wall of the roller. Alternate spraying and dumping on powder until you're almost done. At the end dump a bunch of powder on the hulls and let it rotate on it's own for 10-15 minutes. This lets the internal water wick out and doesn't let them end up overly wet. This is actually where I got the resting idea I suggested above from.

 

Another trick I sometimes see is to add the final 1/2 to 1 part without any sort of binder. I've taken to doing this, and it acts like flour with baking. The hulls almost can't stick together. The final hulls are sometimes a bit dusty, but quite free flowing.

 

BINGO!!

 

Three of us pyros got together last month to make BP coated hulls using a standard 75:15:10 BP ball milled mix. I measured out 1# of rice hulls and got them spinning in the star roller and added 4# of BP in 8oz increments. The hulls were sprayed with a fine mist sprayer until they stuck to the sides of the roller and the first increment was sprinkled on top slowly. We added another increment of BP and sprayed only when the hulls wouldn't take the BP any longer.

 

Repeat, repeat.

 

Finish with BP with no binder.

 

D

[50AE]

A mistake that could origin from impatience is the hurry to mix the hulls with the composition before allowing the water to drop from them, they must be damp and could be a little tricky. When I did this for the first time, I screened the hulls, put them in a glass of water and let them sink to the bottom. Then, I took them out and poured them on a towel and squeezed them with all my forces to let the water out. I repeated this 3 more times. Finally, I mixed them with the comp and guess what - they weren't completely covered with the comp, meaning they were still overdamp. The comp was damp and it didn't properly adhere to the next batch of hulls.

[AdmiralDonSnider]

Just wanted to give a quick feedback, having tried to realize your suggestions when coating hulls with H3.

 

It now is working a lot better, but I still seem to have about 1/5 of the batch granular, not sticking to the hulls. After letting the hulls fall to the ground in boiling hot water, I used a modified pantyhose to swing the moisture out. Next time I´ll probably swing it for a shorter time, about a few seconds only, to leave more moisture trapped, as I tend to believe that the hulls are a lot too dry when I start adding powder. Thus even the suggested "soaking" stops between the increments couldn´t grant 100% adhesion.

 

I also believe that one should use more water in a smaller batch, as the weight in rotating- by hand in a plastic jar or by machine in a star roller - is less than in case of a large batch and thus the pressure at the bottom may be insufficient to make granular/powdered stuff adhere.

[dagabu]

Just wanted to give a quick feedback, having tried to realize your suggestions when coating hulls with H3.

 

It now is working a lot better, but I still seem to have about 1/5 of the batch granular, not sticking to the hulls. After letting the hulls fall to the ground in boiling hot water, I used a modified pantyhose to swing the moisture out. Next time I´ll probably swing it for a shorter time, about a few seconds only, to leave more moisture trapped, as I tend to believe that the hulls are a lot too dry when I start adding powder. Thus even the suggested "soaking" stops between the increments couldn´t grant 100% adhesion.

 

I also believe that one should use more water in a smaller batch, as the weight in rotating- by hand in a plastic jar or by machine in a star roller - is less than in case of a large batch and thus the pressure at the bottom may be insufficient to make granular/powdered stuff adhere.

 

Sorry, I think I missed something here.

 

Small increments of BP, H3 or whatever have to be added one at a time and spraying needs to be done between coats. If you add to much BP you will not get good adhesion. Think of rolling stars.

 

D

[AdmiralDonSnider]

Yes but I was talking about the hand-coating technique as described in Bleser, which relies on soaked hulls and - in theory - requires no spray bottle at all. I just wanted to argue that you shouldn´t "swing" out too much moisture to make this method work, at least in case of a small batch.

[dagabu]

Yes but I was talking about the hand-coating technique as described in Bleser, which relies on soaked hulls and - in theory - requires no spray bottle at all. I just wanted to argue that you shouldn´t "swing" out too much moisture to make this method work, at least in case of a small batch.

 

No, I understood the point of soaking the rice hulls but you cant get a 7:1 ratio with soaking alone.

 

As Emily Lutilla once said, "Nevermind".

[Ventsi]

Snap! I just ran out of Dextrin and I need to make some more burst today. Can I use Red Gum or CMC as the binder?

I'll make some dextrin ASAP though I need to make the burst today and have it dry by Wednesday.

Edited February 9, 2010 by Ventsi

[Ventsi]

Sorry for the double posting but I really need to know the answer. Just a yes or a no, Especially the CMC.

Thanks

[AdmiralDonSnider]

Have never used CMC, but I assume you can use red gum, with some sacrifice to adhesion. Dextrin is available from every pharmacy, so if you really need it the elevated prize of 100g won´t kill you.

[Bonny]

Sorry for the double posting but I really need to know the answer. Just a yes or a no, Especially the CMC.

Thanks

 

 

You could just go with RG bound pulverone/riced BP without a carrier. It can be quickly prepared and should dry fast using alcohol as the solvent. Or, get that oven going and you'll have dextrin in a few hours anyway.

[dagabu]

Snap! I just ran out of Dextrin and I need to make some more burst today. Can I use Red Gum or CMC as the binder?

I'll make some dextrin ASAP though I need to make the burst today and have it dry by Wednesday.

 

Vince,

 

Put 8 oz of warm water in a bowl and add a pinch of CMC into it and stir, if it starts to gel, add a little more warm water. It should not gel but feel like the water is 'thick' to the touch. Let it sit for 30 minutes and feel it again, add water if needed.

 

Pour it into your spray bottle and spritz the rice hulls with the CMC water and add small increments of BP. The CMC will work fine this way (a little strange but it will work) but will make a sticky mess if you use in in the dry ingredients.

 

D

[Ventsi]

Sorry but I was in a hurry, ignorant and needed the stuff ASAP. I decided to mill the burst with 1% CMC and the process worked wonderfully, the carer was stickier than normal but perfectly usable.

[dagabu]

Sorry but I was in a hurry, ignorant and needed the stuff ASAP. I decided to mill the burst with 1% CMC and the process worked wonderfully, the carer was stickier than normal but perfectly usable.

 

Cool, I am glad it worked for you.

 

D

[AdmiralDonSnider]

Today I gave H3 coated rice hulls another try. The stuff I´d made so far performed well in shells, but there still was about 1/5th of comp unadhering, forming a powder layer in the bottom of my storage container. The hulls weren´t too durable either when handled and packed, with coating easily breaking off.

 

This is all connected with the fact that I had made my hulls too dry to make a 4:1 ratio adhere.

(see my method: post #11)

 

I don´t know who came up with the suggestion to get rid of moisture after soaking the hulls, but that had been the exact mistake of the method I used until today. If you don´t "swing" the moisture out like I did (with a sock or a pantyhose) you get the exact moisture content needed to reach 100% adhesion.

 

After soaking (hulls fall down) I filter through a screen, wait a couple of seconds and then transfer the wet (rather than moist) hulls into a cylindrical container (about gallon size) which simulates a star-roller when turned by hand. Then I add the break in small increments and keep rotating the container, then add again... In case the hulls seem to dry I give ´em a few careful sprays. Works like a charm! Try this if you don´t have a star-roller. (I´m sure this won´t work up to a 8:1 ratio, but it´s still useful)

 

Thanks for all the help on this!

Edited July 7, 2010 by AdmiralDonSnider

[dagabu]

I don´t know who came up with the suggestion to get rid of moisture after soaking the hulls, but that had been the exact mistake of the method I used until today. If you don´t "swing" the moisture out like I did (with a sock or a pantyhose) you get the exact moisture content needed to reach 100% adhesion.

 

True, if the hulls are spun, you will not get a complete coating on the rice hulls. However, that is not what most of us are looking for though. If the hulls are damp and you add comp in increments, you get hard hulls with several coats of comp. It can be more durable and chip less.

 

That being said, I found no difference between the two methods when used for break, both seem to work as well.

 

I have changed my comp to include 1% CMC for all of my hulls since they become very hard and the comp will not chip off when compacting behind inserts.

 

Thanks ADS!

[AdmiralDonSnider]

True, if the hulls are spun, you will not get a complete coating on the rice hulls. However, that is not what most of us are looking for though. If the hulls are damp and you add comp in increments, you get hard hulls with several coats of comp. It can be more durable and chip less.

 

That being said, I found no difference between the two methods when used for break, both seem to work as well.

 

 

Dagabu, I didn´t get why this isn´t what you are looking for. Aren´t you looking for a complete coating? Or were you just saying that you´d rather use a roller for simplicicity - I´d also use one if I had one ;-).

 

Can you work out the difference between the "two methods" you were talking of?

[dagabu]

Dagabu, I didn´t get why this isn´t what you are looking for. Aren´t you looking for a complete coating? Or were you just saying that you´d rather use a roller for simplicicity - I´d also use one if I had one ;-).

 

Can you work out the difference between the "two methods" you were talking of?

 

Sure, I would love to comment

 

I LOVE the look of single pass coating of rice hulls. They are much darker, better coated and hold a crap load of comp. The downside is that the comp over whets and shrinks, cracks internally, powders off, isn't as durable and can lead to crushed grains which makes them less consistent.

 

I have NOT tried this with the addition of 1% CMC, so that may fix all of those issues but I find the rolled and tumbled rice hulls to be harder, much more durable and consistent.

 

That said, if it is for filler only, who cares what it does, if it is not for break it does not matter what the consistency is. There needs to be minimal powdering if it is to be used for burst due to the fire paths between grains so a harder and more consistent coated hull will always provide better break.

 

This may not be a problem as we are just starting to build shells but after a while, we all want to have the perfect break, perfect stars... the perfect shell. That cannot be done by cutting any corners, a slow and determined method must be followed for that to happen.

 

This does not mean you are wrong, these are my experiences, with 1% CMC, the wet hull method may prove to be better then multi-layering