Granulating black powder

[Tim1877]

I just granulated some black powder tonight using red gum and alcohol using 1% red gum and denatured alcohol and a 4 mesh screen. I normally use 5% dextrin and water with the same 4 mesh screen,I ended up with a lot more fines than usual and it's really soft grains but it is lightning fast just wondering if I need more red gum or am I missing something else here I love the quick dry time of the alcohol though

[Mumbles]

Red gum does not give as durable of grains as dextrin. You could try to increase up to maybe 2% red gum and see if that helps at all. 1-2% is the range I normally see people quote. Regardless it's usually reported to be softer, which is a deal breaker to some. Some charcoals containing resins are also suggested to contribute.

[Tim1877]

I used paulownia for the batch I made with red gum,the batch made with dextrin I used commercial air float hard wood mix ,the paulownia was much faster just really soft for my taste

[dagabu]

Paulownia sure is a soft charcoal and hard to consolidate so its not surprising that you are getting softer grains. I would use 2-3% of red gum to bind it if that is all you have but I prefer white or yellow dextrin myself.

[dynomike1]

You know i have noticed that Phenolic speeds up the burn rate in star comps. I wonder what it would do in BP?

[dynomike1]

Aw hell i was just reading another article and it dawned on me that using Phenolic the grains would probably stick together.

[Carbon796]

1 to 1.5 % of SGRS works very well with paulownia, for screen granulated BP.

[MadMat]

This may be slightly off topic, but since they were both mentioned.... Is SGRS a considerably "stronger" binder than dextrin? All I have used so far is dextrin and NC lacquer.

Edited February 25, 2017 by MadMat

[OldMarine]

I've used both and it seemed to me the dextrin bound grains were harder. On the other hand, I like SGRS better for making match because it allows it to be more flexible without flaking. YRMV

[Seymour]

Gum Arabic in my opinion is stronger than Dextrin and obviously many, many times stronger than Red Gum. You only need 1-2% Gum Arabic to make durable grains. With Gum Arabic 2% makes grains so hard that if you tried to break them between your fingers you can easily get corners of the grains piercing your skin. A painful experience I assure you.

And with Paulownia BP, in my opinion, it is very, very difficult to come up with a reason that you need it to be more powerful than it is with 2% Dextrin or GA, assuming effective milling.

I have pretty much zero interest in using Red Gum as a binder in BP even though I have no doubt that 2% RG can improve the power by introducing a higher energy fuel in a low enough % to not slow down the BP much.

But I like my BP to be tough, not crumbly, relatively dust free grains as well as being faster burning than I need. BP Paulownia, Willow, Cedar, and Plum (to name a few) with 2% Dextrin, Gum Arabic, Soluble glutinous rice starch (SGRS) or Resinox to bind, will all be fantastic quality if they are milled well.

From memory, the 2% Red Gum was often cited to be a useful addition to very low quality BP (like, using commercial airfloat charcoal) to make it a bit better.

And I am of the opinion that low quality BP is usually completely fine to use. I'm not trashing using commercial airflow, or using red gum to bind BP. However I do want to point out that as much as I believe the benefits of adding Red Gum are real, they are not as big a deal as it might seem from some of the literature, and as many others have said, I personally think they are far outweighed by the negative factors that come with crumbly, weak grained BP, so long as you have the option of superior alternatives (such as Dextrin and Willow Charcoal or better yet, Paulownia charcoal and Gum Arabic (or Dextrin).

[lloyd]

Gum Arabic in my opinion is stronger than Dextrin and obviously many, many times stronger than Red Gum.

----------------------------

Ah! Is that the reason why Gum Arabic was used as the basis for the glue of exterior plywood as far back as the 1930s?

 

Oh... wait! That was Red Gum! My mistake!

 

(Like almost all things, it's the _application_ that matters. Straight Red Gum is MANY TIMES stronger - mechanically - than Straight Gum Arabic... but Accroides just doesn't happen to work well as a binder with strongly-alkaline materials) In fact, phenolated accroides resin competes in strength with many 'true' phenolic resins, and is totally waterproof.

 

LLoyd

Edited February 25, 2017 by lloyd

[dagabu]

Good stuff there Lloyd, I got the "and is totally waterproof." part but sure could use the laymans guide to the beginning of that sentence. Sorry, I had a public school education.

[lloyd]

Heh, So did I, Dave! I only know, because I've been doing research into various resins for a contract. There's a difference between "just knowing", and "having to know". <grin>

 

Phenolaldehyde treatments of various resins (both natural and synthetic) in various ways of treatment simply replace certain radicals in the resin molecule with others. But the upshot is that phenolated accroides resin was used for some time for waterproof exterior plywood adhesive. It can also be "thermo-setting", which is not the state of the natural resin.

 

I wouldn't have known that, either, about four months ago!

 

Lloyd

[Seymour]

My personal experience is certainly that in BP Red Gum has never been even close to as strong as Gum Arabic. I've used Red Gum with both Acetone and IPA. Gum Arabic with plain water.

If Red Gum can be stronger than Gum Arabic (which I do not dispute, having been corrected) What am I doing wrong?

 

What do you mean by "Phenolated Red Gum". My understanding was that Red Gum has a high % of phenolic components. Is there a variety of Accroides resin without the phenolic component?

I do understand that there are several grades of the resin (of course, being a natural product, there is variety, as one would expect with Gum Arabic too), and that some are better than others at binding.

So are you saying that in the application of _Black Powder_ Red Gum can be stronger than Gum Arabic? Red Gum is waterproof certainly, at least compared to Gum Arabic, but in this situation waterproof is not a selling point for me, though no doubt it is important for plywood. I want to know how to make Red Gum work better than Gum Arabic for binding strength in BP and Stars. I have never experienced Red Gum binding anything even half as well as Gum Arabic, but I understand that this is a result on my materials and techniques.

The plywood comment does not explain a lot to me. I can think of many many reasons why Red Gum would be used instead of Gum Arabic. Waterproof is the main reason. Who wants plywood that falls apart if it gets wet? Cost may be another. And Red Gum working better in _that application_ is another. But I want to know how to make Red Gum work better as a binder in fireworks. I can get RG A LOT cheaper than GA.

Edited March 8, 2017 by Seymour

[FlaMtnBkr]

What is wrong with dextrin? I don't use any binder and I get pretty darn durable grains. Hard enough to hurt my fingers when breaking up clumps and have never had a need for harder BP grains.

 

Are you milling your red gum and gum arabic with your BP and then adding the solvent? Or mixing the solvent and binder into a solution that is added to the BP? It seems like I normally read of people milling the red gum with the BP and adding the gum arabic with the water as the most common methods.

 

If so, it seems like a viscous solution with the binder seems to coat the BP more while the thin water soaks into the powder. This probably allows less nitrate to be dissolved while also drying quicker since it isn't down in the pores of the charcoal as much. Also, with the binder dissolved in the water it probably allows less nitrate to dissolve since there is already something else dissolved, though these are mainly guesses.

 

It has been shown that dextrin dissolved in water to make a "dextrin liquor" with enough added to add 2% dextrin makes BP that is 20-30% faster than dextrin that is milled into the BP when used in a muzzleloader and measured with a chronograph. At least this is the claim of the person that introduced "dextrin liquor" to the pyro community.

 

Is your powder not that hot? Is there a reason you need the hottest powder possible?

[rogeryermaw]

+1 for no binders. when fully dry i can barely break b.p. grains by hand. i don't have much experience with sgrs. only used it once and really wasn't that impressed over dextrin for water activated stars.

Edited March 8, 2017 by rogeryermaw

[OldMarine]

I pretty much only use a binder if I'm going to coat rice hulls with the mill dust. Alcohol alone seems to work for granulating burst used in smaller shells where you need more density of burst.

Oh, I also use binder in my polverone so it will be extra stiff for filling the perimeter of cylinder heading around the outer stars and casing.

Edited March 8, 2017 by OldMarine

[DavidF]

Regarding alcohol, many of us have different experiences with it. Ned says he gets good hard grains with denatured alcohol. I never have, regardless of the charcoal used as the BP base. It was always a waste of time. But, American denatured alcohol is not the same as Canadian denatured alcohol. Isopropyl alcohol of 70% purity will give fairly hard grains of good speed. Isopropyl alcohol of 99% purity gave me the same dusty, barely-granulated product I got from my denatured ethanol. Acetone gave the same poor results as the 'pure' alcohols gave. I have done quite a few experiments with this and proven that it is the water in the alcohol solution that solubilizes some of the potassium nitrate, allowing the nitrate to act as a binder.

 

It is said that the volatiles contained in hot BP charcoal also act as a binder in alcohol-damped black powders. I have found no evidence of this in any of my experiments. I have pored over thousands of pages of information on black powder over the years and seen no study showing volatiles in charcoal to be active as binders in black powder. On the contrary, commercial powder makers use water to activate the potassium nitrate binder. The problem with using 'just' water as a solvent for the binder is in tightly controlling the total moisture content and the drying conditions. It's easy to screw it up. Using 70% isopropyl alcohol is the best way I know of to control the water to advantage when screen-granulating black powder.

[Boophoenix]

Thank ya for sharing Dave. I'm fairly certain we've discussed this some and I was one of those who had sniffed the alcohol and thought the volotilities may have a roll in binding.

[dynomike1]

I have tried 70% alcohol with erc and i couldn't get hard grains out of it, so i still use 25/75 alcohol water with Dextrin and i get hard grains, and i think as good a powder as anyone. As far as drying time i put mine in the sun in a Beer flat and it's dry that evening, maybe sooner. If you need it quicker than that maybe you are not making enough. I think that straight alcohol may be fine in certain applications when pressing. When i question Tim about ERC he told me that i had to evaporate the alcohol out of it quick to keep the KNO3 from dissipating.Well i still didnt get hard grains and my BP was still weak. So if i can find Red Alder or Paulinia that is what i use.