AzoMittle Posted November 29, 2014 Posted November 29, 2014 (edited) Hey all, I need help with microstars, I can't get them to actually work as intended in a gerb/fountain as colored sparks / jellybeans. General metallic/charcoal sparks work fine but I want that touch of color. I've tried a few things and am having trouble figuring out where I went wrong. I initially pushed the comp through an 8-mesh screen to get particles in the size range of rough powder to grains of rice and then sized them via wire screen. The rough powder always burns up and simply turns the gerb a red color. The larger particles do the same. When using the larger ones I have noticed a tendency for the comp to turn solid and plug up the nozzle; initially I tried fixing this by using a slightly larger tube, this did not have any noticeable effect on the given problem and only caused the larger particles to color the gerb flame. I have noticed in a few of Ned Gorski's / Harry Gilliam's / (some other person I can't remember the name of) they mention the need to "lightly tamp" the composition. I began by using a rubber mallet and rammer and then slowly decreased pressure to hand pressed (hard as I could), then to hand tamped (just enough to keep powder from falling out the tube when turned upside down) and even down to simple loose powder. None of these caused the microstars to shoot out like sparks and only changed the rate at which it burned. Mumble's has posted in a few places that the Chinese make their microstars from NC and a colorant, this is then extruded and sliced to size. Could the problem be with my formula? NC + SrCO3 should be much slower burning than a proper star mix I would think. The formulas I have used are below. I have tried known red and green star formulas with the same results as above. Silver Fountain (Harry Gilliam's modification of John Werner) (I have tried also tried a charcoal and a 'gold glitter' without success.)=============51....Potassium Nitrate10....Sulfur09....Charcoal, Airfloat30....Titanium Red Microstars (My derivation of Bill Ofca's Brilliant Red, needs work (does not add to 100))=============52....Strontium Nitrate08....Strontium Carbonate17....Magnalium09....Red Gum06....PVC06....Dechlorane03....Phenolic Resin10....Nitrocellulose Edited November 29, 2014 by AzoMittle
schroedinger Posted November 30, 2014 Posted November 30, 2014 Did you use a nozzle which is big enough to let the stars go through?How hard where your microstars? This sounds like they are breaking up during pressing and the fragments burn up inside the casing. Did you use a binder on the matrix or just dry mix?
FlaMtnBkr Posted November 30, 2014 Posted November 30, 2014 It does sound like they may be being crushed down to a powder. Screened composition is not usually very dense. The burn rate of the star comp may also be too fast so they are burning up inside the tube. This is a fairly common problem. You may try priming the stars with a prime that is slower than the base comp. This way the microstars have a chance to burn outside the tube.
Col Posted November 30, 2014 Posted November 30, 2014 did you use an angled rammer for the choke? If the stars cant find their way out they`ll burn up in the tube.
AzoMittle Posted November 30, 2014 Author Posted November 30, 2014 Did you use a nozzle which is big enough to let the stars go through?How hard where your microstars? This sounds like they are breaking up during pressing and the fragments burn up inside the casing. Did you use a binder on the matrix or just dry mix? Initially I used a ½" tube with a 50% open nozzle. I switched this out for an unchoked ¼". Both should have been large enough but I have doubts about the nozzle forming sharp inside edges for things to get stuck on. Microstars were not very hard, that's why I added the phenolic resin. They take little effort to crush by hand. I have a ⅛" rammer, I can try pressing and extruding. No binder on the matrix. It does sound like they may be being crushed down to a powder. Screened composition is not usually very dense. The burn rate of the star comp may also be too fast so they are burning up inside the tube. This is a fairly common problem. You may try priming the stars with a prime that is slower than the base comp. This way the microstars have a chance to burn outside the tube. Will do. Any specific prime you would recommend? Would meal powder be too fast? did you use an angled rammer for the choke? If the stars cant find their way out they`ll burn up in the tube. No, just flat with a hole drilled in the middle. I also tried unchoked. When I have time I will make an angled rammer, that's just a good idea in general.
FlaMtnBkr Posted November 30, 2014 Posted November 30, 2014 Hand mixed meal/ green mix would probably help. Or a charcoal star comp like C6 or even a glitter.
enanthate Posted December 3, 2014 Posted December 3, 2014 Why not replace PVC with Parlon? Better binding, you do want them hard.For priming, I would use handmixed(slow) BP like Flam said, with 1/3 of the starmix mixed into it. I assume you have tested the red mix, and that it works with NC. Would adding a bit more NC make a difference?
Mumbles Posted December 5, 2014 Posted December 5, 2014 Why not replace PVC with Parlon? Better binding, you do want them hard.For priming, I would use handmixed(slow) BP like Flam said, with 1/3 of the starmix mixed into it. I assume you have tested the red mix, and that it works with NC. Would adding a bit more NC make a difference? I doubt switching from PVC to Parlon for the chlorine donor/binding would help at all. You are aware that parlon binding is well known to increase the burn rate I assume?
jessoman Posted December 5, 2014 Posted December 5, 2014 (edited) I assure you bill ofca's comp doesn't "need work" haha. Prime them. Nice hot metallic prime will give metallic sparks and a bit of delay. Rough mix hard wood bp with a 5% dex. I would prefer metallic prime with this combination but that's just my taste. MgAl particle size, did you use the correct size? Edited December 5, 2014 by jessoman
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