PyroGnome Posted July 14 Share Posted July 14 Hi! Just to introduce myself, I've been making display shells as a hobby since I was 12, and was a junior member of the HPAA back then, and the PGI although I never made it to a convention due to monetary constraints. Went to college, and rental properties forced me to stay away from the hobby for a long time. I picked up oil painting a few years ago and was hunting for oddball pigments that nobody makes paint from anymore, and found paris green at pyrocreations Decided what the heck, I have my own house finally and a gigantic detached garage that I don't do anything with, and picked up some things to make glitter comets while I was there and 6 months later I'm making 3lb stingers, testing star comps, finally built myself a star roller so I can put more of the Bleser book I've had since '91 to good use, and trying to work out the first HPAA shoot I'll be able to go to when I re-join. 🙂 I'm happy about my decision to pick it up again. Metal powders cost roughly 4x their price to ship back then (meaning I could never afford anything the club didn't buy a bunch of) so seeing that things were back to normal on that was nice too. Anyway.... I searched the forum and didn't find this so apologies if it's been posted. I found it amusing. I stumbled across this paper a few weeks back while searching for something else. Since my only star pump is a 1.25" round shot crosette and I'm probably not ordering a press for another couple of weeks, I went with loose compaction and thin walled (somewhere between #20 kraft and tissue) tubes. A normal strobe mix might be likely to explode under those conditions but this stuff is more likely to blow itself out it seems. I also lack nitrocellulose although it seemed like this probably wouldn't matter for a dry test. It probably had something to do with the difficulty in ignition, although the paper recommends a nitrate-based igniter comp which could be anything. Silicon / MgAl / etc. Formula is as paper, using -325m MgAl Edgewood Chemical Biological Center, "EFFECT OF STRONTIUM NITRATE ON EXTREMELY SLOW STROBE COMPOSITIONS", 2017, ECBC-TR-1431 Lighting a ~10g quantity in a tissue tube directly with a propane torch (after a couple of very hot burning stars failed and I was starting to doubt whether it would even burn without NC) took long enough that the sulfur melted down and it ignited without warning and a fast steady white flash. was produced which died down to a thin flame that remained for a while before going out. I tried some leftover fountain comp that needs to be burned that spews lots of molten iron slag and this was enough to light it normally. I'm guessing meal + 10% silicon would work, too. I cut out the ignition because my camerawork would cause severe nausea ;-). The fountain comp on top was lit about 6s before, it produced a single weaker flash of light, then there was a fairly satisfying pop and flash at about 18s after the probable ignition time. I didn't use the full 10g the paper does, and this was the smallest, so I suspect this consumed the remaining comp and it only had the one good flash in it after ignition. I was kind of surprised I got strobing at all. The next day I checked the tubes and they still appeared to be full of some silvery metal, with some odd green / blue green / yellowish fine crystalline protrusions. Maybe some condensed sulfur vapor from lower in the mix? I don't know. The tissue paper below the burn line was unscorched, as were the cardboard squares I'd taped them to which was unexpected, but this is a weird mix. Have about 10g left so I'll probably bind it with parlon / acetone. I won't be putting a ton of dead weight on it but parlon bound comps seem to collapse in on themselves like neutron stars as soon as the acetone is added so it should at least be closer. If parlon works I'll probably make some slow strobe pots when my 80-200 mesh MgAl arrives (100 mesh seemed to be the sweet spot in their testing) otherwise I'd just as soon avoid NC for now. I haven't tried the potassium nitrate modifications yet, which keep the strobe frequency fairly slow (4-5 minute burns for 10g of comp) still but likely make it more ignitable. They didn't try it but I'm also going to see what happens with a partial barium nitrate substitution. I could see these being amusing made larger and placed kind of randomly in clearings in a field of corn or the edge of the woods (maybe in plasma-cut steel barrels to cast some weird shadows and keep slag from igniting anything) around halloween. These were based on the "orion's flashing guns" formula as the paper mentions. On a related note I've found two blue strobe study papers online which use materials mixed with ammonium perchlorate that I'd rather not add to anything, although the tetramethylammonium nitrate + AP + basic copper carbonate looks like it's the least sensitive of the mess and most promising. Since I've seen it come up here before, copper benzoate + ap vastly increases the impact sensitivity of the mix, same for friction to a somewhat lesser extent, according to one paper. It's not as bad as pure copper but it is worse than anything else except CuO + a percentage of added sulfur. Anyway, cheers all, Hope someone finds this interesting. slow_strobe_18s_h264.mp4 Link to comment Share on other sites More sharing options...
PyroGnome Posted July 14 Author Share Posted July 14 Here's the torch-lit (pre-heated) identical composition for comparison, strobing nice and fast. strobe_torch_lit.mp4 Link to comment Share on other sites More sharing options...
PyroGnome Posted August 10 Author Share Posted August 10 Tried some pressed in a 3/4"x4" NEPT tube at ~8000psi with an increment of slaggy KNO3 vesuvias style mix on top to ignite and another increment of BP. This time I suspect the KNO3 melted down into the upper layers of strobe, because there was a very steady decline in strobe speed over time until it was seconds apart on the last 4 which also produced good sized pops. Now that I have a press and got some coarser magnalium in, I'm going to try to duplicate the longest (~1 minute) strobe delays of the paper, but that's for later. This is an admittedly sort of useles comp unless you want a high altitude strobing parachute flare. Sorry for lack of video, it's too big and I haven't made myself a vimeo account yet Link to comment Share on other sites More sharing options...
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