D1 NC-bound

[SharkWhisperer]

Summary: NC works great to bind D1, dries quickly for durable stars ready within hours, but is a more expensive option than dextrin/water binding.

Was testing out a bag of old FWC -325 atomized Al I found hidden away on a shelf & wanted quick answers so I bound up some standard D1 comp with NC lacquer, rolled & cut a patty, and ran some scraps out of a stargun.

NC worked just fine as a fast-drying D1 binder. No concerns with overwetting quenching the effect. Allows charcoal comps to be easily cut into stars vs pressing or rolling. No dryer box or long waits needed. Earlier threads have mentioned NC-bound D1 but I've never heard about it from somebody that actually did it tried it out.

Standard D1 formulation with KNO3, charcoal (homemade willow) and S milled for a few hours (many don't bother milling D1 comps) before screening in the Al and NaHCO3. Left out the dextrin. Was going for around 3% NC final concentration, but overpoured and had 4% NC final, after acetone evaporation. Rolled out a small batch (100g) to 1/4" and cut 3/8" x 3/8" squares. Dried on an 8-mesh screen in the sun for an hour or so, flipping once. After cutting but before finishing/drying/separating, I lightly sprayed both patty surfaces with 91% IPA and sprinkled/patted with leftover prime scrap from rubber stars--so, a mixture of hot perc prime and a slower KNO3 prime, both containing 5% MgAl, 2-3% Si metal, and 5% red gum I use as a binder. Priming is probably not necessary but it makes the patty less sticky to handle. Snapped pieces apart after mostly dry & put in front of a fan for a bit until no smell of solvent detectable. NC was derived from Hodgdon's International shotshell powder (double-base).

Shot was about 12g of smaller pieces and edge scrap that was lifted hard with 2 grams of 1Fg Goex BP from a 1.25" x 8" iron gun bore.

Happy with the comp in general, and NC as the binder, so will do a larger batch with more attention to star size and shape uniformity. Probably no need to prime at all. Minimal drying time; NC/acetone allows making charcoal-based glitter stars and shooting them within hours. Stars are tough and can be expected to be somewhat resistant to atmospheric moisture. May try 2% NC final to see if that is sufficient for binding, just to save costs on NC (i.e., 20g smokeless powder/kilo D1 comp instead of the 40g/kilo comp I used here).

Phone cam vid is subpar but you get the idea...

Edited May 17 by SharkWhisperer
Clarify details; Readability

[LiamPyro]

Interesting experiment. This might be a good binding method for producing microstars sliced through a screen, "mouse turd" style. I had wondered about binding charcoal star comps with NC, primarily for the purpose of making a syrup/paste to coat shells and make them into meteors. I supposed it would work but that the lack of water in the process would result in a slightly different effect by allowing less absorption of the KNO3 into the charcoal, seeing as KNO3 is less soluble in acetone than it is in water. 

[Zumber]

On 5/15/2024 at 11:06 AM, SharkWhisperer said:

Summary: NC works great to bind D1, dries quickly for durable stars ready within hours, but is a more expensive option than dextrin/water binding.

Was testing out a bag of old FWC -325 atomized Al I found hidden away on a shelf & wanted quick answers so I bound up some standard D1 comp with NC lacquer, rolled & cut a patty, and ran some scraps out of a stargun.

NC worked just fine as a fast-drying D1 binder. No concerns with overwetting quenching the effect. Allows charcoal comps to be easily cut into stars vs pressing or rolling. No dryer box or long waits needed. Earlier threads have mentioned NC-bound D1 but I've never heard about it from somebody that actually did it tried it out.

Standard D1 formulation with KNO3, charcoal (homemade willow) and S milled for a few hours (many don't bother milling D1 comps) before screening in the Al and NaHCO3. Left out the dextrin. Was going for around 3% NC final concentration, but overpoured and had 4% NC final, after acetone evaporation. Rolled out a small batch (100g) to 1/4" and cut 3/8" x 3/8" squares. Dried on an 8-mesh screen in the sun for an hour or so, flipping once. After cutting but before finishing/drying/separating, I lightly sprayed both patty surfaces with 91% IPA and sprinkled/patted with leftover prime scrap from rubber stars--so, a mixture of hot perc prime and a slower KNO3 prime, both containing 5% MgAl, 2-3% Si metal, and 5% red gum I use as a binder. Priming is probably not necessary but it makes the patty less sticky to handle. Snapped pieces apart after mostly dry & put in front of a fan for a bit until no smell of solvent detectable. NC was derived from Hodgdon's International shotshell powder (double-base).

Shot was about 12g of smaller pieces and edge scrap that was lifted hard with 2 grams of 1Fg Goex BP from a 1.25" x 8" iron gun bore.

Happy with the comp in general, and NC as the binder, so will do a larger batch with more attention to star size and shape uniformity. Probably no need to prime at all. Minimal drying time; NC/acetone allows making charcoal-based glitter stars and shooting them within hours. Stars are tough and can be expected to be somewhat resistant to atmospheric moisture. May try 2% NC final to see if that is sufficient for binding, just to save costs on NC (i.e., 20g smokeless powder/kilo D1 comp instead of the 40g/kilo comp I used here).

Phone cam vid is subpar but you get the idea...

 

Is star burned too fast?? Seems less glittering/strobing effect in trail.

[SharkWhisperer]

3 hours ago, Zumber said:

Is star burned too fast?? Seems less glittering/strobing effect in trail.

This was the smaller pieces & non-uniform pieces, with added crumbs. Milling also increased comp burn rate (and accommodates the lack of additional KNO3/charcoal integration using water solvation). Most folks don't mill D1 if starting with fine chems including charcoal.

Larger more uniform stars burn very nicely at speed. Might try out some Alcoa 120 for a mixed tail effect.

Screen-cutting (to any size including mouse turds) is possible but like many things acetone-bound, the quick drying makes timing important to not make a sticky mess or need to try to push an overdry slab through the mesh. Adding paint thinner or MEK to acetone will increase your working time, if desired. I don't bother but do keep a spray bottle of acetone handy--note that even if your bottle is acetone-resistant, it's a good bet that your sprayer internal components are not and will clog, so acetone bottles need pre-testing. I've been using the same one for years now (after killing/clogging many).

Nice way to quickly pound out piles of charcoal stars, without needing to press them. No hydraulic press? Syringes and ramming tools get tedious quickly. Cutting water-wet charcoal comps can be done but folks often overdo it on the water part, with detrimental effects. I guess a few folks roll charcoal comps but I usually avoid that.

This makes nice hard stars that probably store very well. Without fastidious care in my humid environment, charcoal+metal comps/stars tend to suck up a ton of water during storage. Some leftover C6 + MgAl (+10%) stars & comets from last 4th (dextrin-bound) that were laying about in a plastic bag unprotected predictably burned pretty anemically in my firepit.

NC is pricier than dex by far, especially with the jacked up prices on everything since after the flu times (just 5 years ago all speeds of retail fuse were $2.99/20 feet online). In the US you can get a pound of double-base smokeless powder (mostly NC, variable amounts of NG) on sale for $20-25/pound sometimes. Think I paid around $15 per bottle last decade. Cheap smokeless is now around $30-40/pound. Yeah, I appreciate that's pricey compared to most hobbyist chems. For example: https://www.midsouthshooterssupply.com/dept/reloading/smokeless-powder?sortby=pricelowhigh&itemsperpage=30 . And buying 4 or 8-pound bottles doesn't really save much money. At 3% final NC concentration, one pound (454g) is enough to bind up 15 kg (33 pounds) of finished stars. Many hobbyists will take quite awhile to burn through a pound of NC unless they're DE/crackle addicts. I'm inpatient and often prefer using fast-drying organic solvent binding approaches vs cheaper water-based.

[rellim]

Glitter stars with baking soda readily absorb water. I left some well-dried Winokur 20 stars out on the bench and in two days they could be easily crushed between thumb and forefinger. I too have switched to nitrocellulose (celluloid) at 4%.

[DavidF]

This seems like a great plan! I wonder how it would work with plain charcoal stars like tigertail or spider stars. 

When I cut parlon-bound stars that are wetted with acetone, I use the Ziploc Freezer Bag method. I knead the screened, dampened mixture in the closed bag, poke holes in the edges and corners to let air and vapors out, and roll out the patty in the bag. Then I cut the bag away, and let the patty surface air dry a bit, which also stiffens up the patty. Once the surface stickiness is gone, they become easy to cut. I wonder if this method would work with NC binding too?

[SharkWhisperer]

DavidF, can't see why not. For cut rubber/parlon stars, and NC binding for DEs and now charcoal-based (e.g., D1), I stir the binder/solvent in a tub, and roll out the ball of moist comp between sheets of wax paper to desired thickness for screen or hand cutting. Cardboard sheets under/atop make flipping the patty easy. Old pizza boxes work great.

NC/acetone isn't really any more sticky than parlon/acetone and 'moist' comps handle easily once the surface skins over slightly.

Don't see why you couldn't roll it out in a baggie, too, if you don't lose too much to sticking. Personally I prefer the tub mixing/open rolling for uniform solvent evaporation--you can always put the top on a tub or cover the patty with plastic wrap or wax paper for a short while if you need to step away for a bit.

Edited May 25 by SharkWhisperer
spelling

[SharkWhisperer]

Update: It is possible to use too much NC binder.

I upped the NC to 5% final in standard D1 (-325 atomized Al) using freshly made 10% NC/acetone (w/v; double-base). Cut D1 square stars 1/2" x 1/2" x 3/8" thick, dried, and tested 10g in a stargun, launched hard. Stars burned super rapidly--so fast that the glitter effect was mixed in with the BP ejection flame. Single-star unconfined tests showed they burned almost instantaneously, cracked audibly--similar to an oversized DE but nowhere near as loud, with chunks flying several feet. Frame-by-frame, a pure-yellow NC flame is apparent as the star first ignites and fragments, quickly replaced with 2-3 foci of very brief Al glitter effect. Stars were gone almost instantaneously and the visible glitter effect was badly muted. Tried to upload a multi-panel jpg photo file of the sequence but it won't reproduce online for whatever reason.

While NC can be used to bind charcoal stars, D1 in this case, care must be taken in selecting the final NC concentration. At 4% NC they burned quicker than dextrin-bound D1 but were serviceable. At 5% they disappeared too quickly for use in true D1 shells, fragmented audibly, and the glitter effect was largely lost. I am guessing that my originally intended final NC concentration of 3% (or maybe less) will produce more of a classical D1 effect, as intended. At 5% NC they burn too quickly for standard use, and am guessing that fuel is even way too hot for quick-drying go-getters. Somewhere around 2-3% final NC concentration may be the best range to target.

Eye protection is essential.

[Richtee]

Huh... to me that would be an unexpected effect with a higher NC percentage. seems to me they’d end up flaming balls. (OK  no jokes, please)

But I defer to your experience.

[SharkWhisperer]

Here's the video of a static D1 5% NC star burn test. You can hear it pop & see it fragment if you go frame-by-frame. JPEG of frame sequence didn't upload correctly...

At 4% NC they burned a little faster than desired but would be functional as stars >3/8" (9 mm)

 

 

. Will try originally targeted 3% NC final and see if that's the sweet spot.