Low-NC & No-NC Crackle Mixes

[SharkWhisperer]

Goal: Compare regular (5% NC) to crackle/DEs made with reduced NC (2.5%) and no NC, with the binder balance being phenolic resin (PR).

 

Formulations:

Base Composition, taken from many others' experiences

 

35% Bismuth Trioxide

40% CuO

15% Mg/Al, -200+325

05% Al, spherical, -325 (44 micron average)

 

The remaining 5% (total 100%) was either 5% NC final, 2.5% NC/2.5% PR, or 5% PR, all using an equivalent volume of acetone as solvent. When PR was used, it was screen-mixed with the other solid components before binding with NC/acetone or just plain acetone.

 

For adding NC, I calculated the volume of NC 10% using acetone's specific gravity (density=0.791 g/mL); I did not account for/measure the actual density of the NC10% solution, which was of course greater than that of pure acetone alone. For a 100 gm batch, 25 ml should contain 2.5g NC; since using a scale instead of a graduated cylinder (and good luck getting all of that measured volume of viscous NC/acetone out of your cylinder), I calculated approximately 31.25g NC10%/acetone contains 2.5g NC. For larger batches, scaled upwards accordingly. For example, 150g batches of 2.5% NC final used 46.88 g NC10%/acetone.

 

Making PlayDoh for Screen-Granulating:

 

2.5% NC & 2.5% PR Crackle: I'd done this previously, as well as many, many batches of DEs using typical 5%NC final (which involves a LOT of acetone and evaporation waiting time). With 2.5% NC/2.5% PR, I haven't had any real issues. Acetone evaporates pretty quickly, so you need to be on the ball and ready to move as soon as the mixture becomes a consolidated, minimally-sticky ball similar to thick dough. My impression in two batches of 2.5% NC/2.5% PR was that the rolling/screening stages happen a lot faster than when making 5% NC final DEs. On my first batch of 2.5% NC/2.5% PR, I was hasty and lost a fraction to sticking to gloves/container/wax paper during rolling/priming, but still got decent results/screen cutting using an 8-mesh box. My second batch with 2.5% NC/ 2.5% PR was simpler--towards the end of evaporation, as approaching a congealed workable ball of compound, it was clear when stickiness stopped being and issue and the ball was easily separating from my polypropylene container. Hand flattened ball and dropped it on a pile of hot prime (detailed below--common recipe), rolled out to 1/8" (3 mm for my Euro and Aussie colleagues) with a hot prime top dusting, reprimed the backside "wet" spots and pushed it through an 8-mesh screen, and immediately re-screened it through the 8-mesh before allowing to dry and then sizing. No real problems. The comp behaved almost exactly like regular crackle with 5% NC final, though my impression was that it dried out faster once rolling/rolled and you needed to move a bit more quickly. On a heavily (initially) primed patty, my returns,not counting <40-mesh fines, were:

 

Size +8-4 = 15%

Size 8-10 = 49%

Size 10-20 = 20%

Size 20-40 = 16%

 

I used a lot of prime, so the fines were a mix of prime and crackle, and burned as such--might be fun for fuse. First hot prime was perc 70%, 15% hardwood airfloat, 9% red gum, 6% MgAl -60, and +5% Si 200-mesh. Adhered with 91% IPA. Second dusting was with 67% KNO3 BP with a little MgAl and Si added, and 5% RG to get it to stick, again using 91% IPA.

 

 

5% PR/No-NC Crackle: This was my first attempt at all PR crackle, and I didn't expect much difference from low-NC crackle. Man, was I wrong. First, I used the exact same mixture as above, with the only exception being that pure acetone was used for binding (No NC) and the 2.5% final NC was replaced with extra phenolic resin (final concentration 5% total). I even used the exact same volume of acetone to mix/bind as I had with the 2.5% NC batch (46.88g acetone), to avoid the potential confounders of solvent volume and additives (Dollar Store fingernail polish remover; probably has some water or other impurities in it though it says "100% acetone"...ChiComs, ya know). Well, I broke two popsicle sticks just trying to get the initial mix wetted---stuff was like working with concrete. And unlike a uniform slurry that developed an NC skin that we all know so well, this mixture never formed a uniform slurry. At all times, until the very end, there was a thick pile of wet-sand on the bottom of my container and a dark black solution above it (suspended low-micron CuO?). You could pull up a spoonful of the mix at any stage until the end and it was like a chunk of silvery concrete that the acetone just dripped off of. Anyways, after forever of stirring waiting for satisfactory evaporation, this dough-ball was apparently ready to go. Very ready. You could not work fast enough before it became crumbly. The acetone did not remain permeant, but instead pooled on the surface at every step until the end. Rolling a congealed doughball was a trick as the stuff dried before my eyes. I did get it rolled out and primed, with an acetone spray to assist binding, but it was a light initial prime and pieces of the sheet would break off at the slightest disturbance before making it to the screen. Seemed delicate as hell. Even thought to abandon screening and simply cut the patty, but that would have ended the experiment. Anyways, got the patty on my 8-mesh box and it was damn near dry by the time I'd pushed all into the gaps. But not quite dry and still very delicate, as I noted when re-passing it through the 8-mesh screen again before drying and sizing. Before overnight drying at ambient temps, the granules were pretty delicate and easily crushed between fingers (unlike the 2.5% NC which were very hard to the touch, even when they still smelled of solvent). After thorough drying, the granules of all sizes were pretty tough. The granule size histogram reflects their initial delicacy, with not a single granule being retained on the 8-mesh screen after two passes during processing:

 

Size +8-4 =0%

Size 8-10 = 30%

Size 10-20 = 47%

Size 20-40 = 23%

 

There was also more overall loss of starting material with this second approach. Because I did not weigh my prime, the weight of prime+crackle fines is pretty meaningless. I didn't have notable sticking to the mixing container, but did have more notable sticking to the wax paper sheets that I rolled out the patties between while priming, and chunks that rapidly dried could have been lost en route to the screen box. The first NC-containing batch definitely took up more prime during roll-out and initial screening than did the No-NC/5% PR batch.

 

Performance. I haven't yet done a side-by side prime/dry/shoot of the two batches and today it is raining here. That said, my earlier batch of 2.5%NC & 2.5% PR crackle, once primed, had zero blowblinds on hard stargun launches after step priming (probably overpriming) of 8-10 mesh granules. They blew loud and proud. Though my steel stargun could take anything you toss at it, my teeny disposable cardboard 1" mortar didn't appreciate it when I upped from a prudent 12g DE load that shot a beautiful mortar round, to firing 20g DEs with 3 g hot ERC lift, and promptly blew to smithereens. Supplementing the DEs with 3g of crackle fines probably didn't help.

 

A half-gram finger-pinch of 8-10 mesh No-NC eggs dropped into the firepit last night behaved as well as could be desired (repeated several times), and, subjectively, similar to full-NC eggs of that size. In the near future, I'll film and load video comparing equivalent loads of similarly primed 5%NC, 2.5%NC, and 0% NC crackle batches set afire, and you can make your own assessments.

 

Final Impressions: Although there are thousands of phenolic resins (mine was from FWC and baby-powder fine; precise chemical formulation is not certain), working this particular No-NC comp with acetone into a thin patty to screen granulate to crackle was definitely not a relaxing venture. Perhaps a different resin would behave differently. Perhaps using IPA instead of acetone as the solvent would make life easier with a slower evaporation rate. Perhaps a small amount of red gum and IPA would make life easier, but that's a whole new variable tossed into the crackle science. Perhaps cross-linking with a small amount of hexamine would make the wet compound more manageable. Again, a whole new variable added in. Of course ChiCom crackle/DEs uses the cheapest materials available that still work, and almost certainly do not include NC or expensive solvents, if avoidable. The goal to achieve No-NC eggs is laudable, and particularly useful for our fellow pyros in nations where cheap, consistent NC is not easily available, provided the formula works. Others here and elsewhere (USA Pyro, Richardh, Yus, Pyro-gear, and many others) have tested various permutations of established crackle formulas; to eliminate NC, reduce or eliminate Bi (Cu still has toxicity issues, though less worrisome than Pb, etc, and Bi is expensive), and maintain a good loud effect, with varying successes. This is simply an extension of those efforts. Videos to follow next week...

 

 

 

Ok, a video or two...

 

The first is 12g of Low-NC crackle (2.5% NC/ 2.5% phenolic resin) shot as a mine out of a 1" x 6" lightweight cardboard mortar. Loved the effect, but would have enjoyed it 10x more if it was either darker out or if I'd better camera equipment... Granules were 8-10 mesh (3-4mm) with a final size of 4.5-6.0mm after reasonably heavy step priming. All single bursts. All fired. All loud as hell, though the camera cannot show this. I was pleased. Blasted it with 15% by weight of pretty hot ERC BP lift. Added a little bit of fines down the barrel before capping with tight cardboard. Separation between lift and crackle was a corner of single-ply toilet paper.

 

The second video is about 20g Low-NC crackle (10-20 mesh) in same 1" x 6" thin-walled commercial mortar. It was dark, but that didn't help because it was overloaded, assisted by the addition of some fines, and blew to smithereens. Looked like a bad consumer crackle ball but worse. Not impressed. Embarrassed, actually. But they did all light.

 

Coming soon are burst tests of equivalent masses of similarly primed/sized DEs made with classical 5%NC, 2.5% NC (balance PR), and No-NC (5% PR bound). They subjectively do not appear much different to me in reliability, burst brightness, and loudness, but this requires actual side-by-side testing to confirm. Will try to get to it sometime this week.

 

 

 

 

 

 

 

Edited June 7, 2020 by SharkWhisperer

[dlking59]

Thanks for the info. I enjoy reading about tests. Always trying to to improve/find something better.

[Dylman]

Shark Whisperer, I'm very new to this I haven't made anything as of yet & sometimes the abbreviations are unknown to me. What's DE? Thanks for your in depth write up. I do love crackle & when I finally get my act together I'd like to make it. So I do read a lot of info on it or about it especially the different ways it's made. Me not having any chemistry background finds it very interesting that with a little experimenting & knowledge of the chemicals along with how the react together can come up with alternative methods of ultimately producing the same effect. Any info you could shed light onto would be appreciated again thanks for sharing ur trials. Dyl

[SharkWhisperer]

Shark Whisperer, I'm very new to this I haven't made anything as of yet & sometimes the abbreviations are unknown to me. What's DE? Thanks for your in depth write up. I do love crackle & when I finally get my act together I'd like to make it. So I do read a lot of info on it or about it especially the different ways it's made. Me not having any chemistry background finds it very interesting that with a little experimenting & knowledge of the chemicals along with how the react together can come up with alternative methods of ultimately producing the same effect. Any info you could shed light onto would be appreciated again thanks for sharing ur trials. Dyl

Hey Amigo, "DE" is pretty typically used for Dragon Eggs.You'll find a lot of info here and elsewhere if you search for dragon eggs or crackle/"crackling microstars", etc. I usually try to define any abbreviation besides the basics like BP that are (should be) pretty universally understood, but seems I forgot. Also used was IPA, which stands for isopropyl alcohol (rubbing alcohol when sold as a 70% solution, at least in the US...). The more you read, the more you'll learn, and the safer you'll be. And the more fun you'll have. There are several good books available and many tutorials and threads here that will teach you the basic chemistry needed to appreciate the field. And the chemicals that don't play well together--that is critical knowledge for retaining all of your digits :=}

 

Good luck, have fun, but please keep it safe.

[Dylman]

Shark Whisperer, thanks for getting back to me. Yes I've watched a ton of tutorial vids on YouTube that's what got the hooks into me & sent me down this road of possibly 1 day having the ability to make my own. And I've read a ton of stuff. I'm just trying to get all my ducks in a row. So I can start up. I'm 45 and figured it was time to get into a hobby with my free time, plus I've got a grandson I'd like to 1 day get into rocketry. I used to have a blast literally making Estes rocket kits & lighting them off at camp. I've been an enthusiast since a very young age. But I never thought it'd be possible to make my own. So for now I'm just learning as much as I can possibly retain. Had I known there were these groups online I probably would've gotten into it long ago.

[SharkWhisperer]

Shark Whisperer, thanks for getting back to me. Yes I've watched a ton of tutorial vids on YouTube that's what got the hooks into me & sent me down this road of possibly 1 day having the ability to make my own. And I've read a ton of stuff. I'm just trying to get all my ducks in a row. So I can start up. I'm 45 and figured it was time to get into a hobby with my free time, plus I've got a grandson I'd like to 1 day get into rocketry. I used to have a blast literally making Estes rocket kits & lighting them off at camp. I've been an enthusiast since a very young age. But I never thought it'd be possible to make my own. So for now I'm just learning as much as I can possibly retain. Had I known there were these groups online I probably would've gotten into it long ago.

That's great Dylman, and many others have gotten even a later start. I shoot tons of finned rockets (some kits) with medium and low-power (impulse-wise) homemade rockets--mostly F and G equivalents that I make for a few dollars versus the $20+ they get for G motors commercially--ripoff.

 

Probably the first thing to learn (& it often involves a bit of troubleshooting at first) is how to make your own reliable BP from scratch. It's really the foundation of pyro. Crackle's great fun, but even testing DEs requires the use of decent BP for both lift to fire them into the air (need to see them in motion if you plan to use them in shells or mines--essentially anything but ground effects) and to prime their outsides so they take fire reliably.

 

Regarding rockets, the possibilities are endless. Core-burners that whip off the rail and can carry a decent (pyro) payload, endburners that go steady and high....There's a series of threads by HCB from a few months ago where he was sorting out the details of launching an Estes Patriot Rocket with homemade motors that might interest you. He got it working well. Then he went so far as to try to two-stage a pair of kits (one that had fins salvaged after the landing didn't go exactly as planned, tsk tsk). It's a lot of fun. Shoot, with your architecture and drafting background, it'd be a hoot to see what your imagination could create with homemade rockets and motors!

 

Be selective in taking advice from YouTube videos. Some are outstanding, detailed, and clear. Some are outright frightening and filled with bad advice that can get you hurt or worse. I'd recommend Ned Gorski's Fireworking 101 series that he has online for free, as a teaser to get you to pay for access to his website. But it's good info. There's many other sources of good information as well. And there's plenty of experienced folks around that are happy to help you out in getting started. One tip is to do a little homework and self-study before asking questions--the answers might already be readily available to you. The "search" function on this site works really well and if you can't find the answers, then somebody's going to be more than willing to help out.

 

In the interest of keeping this thread about crackle, feel free to pm me or other members, or post new queries on specific topics if non-crackle-related :+}