stix Posted September 20, 2015 Author Posted September 20, 2015 Yes Roger, this one is using m.e.k. After about 12hrs the stars are still soft and can be crumbled if pressed hard enough. The version I did using acetone, they were rock hard at this point. There is a very slight smell of m.e.k. so I guess it hasn't evaporated fully. Interesting, I'm sure I read that m.e.k. evaporates faster than acetone? Anyway, I'll see how they go and do a burn test when it gets dark. Next I'll be making a dextrin/water comp.
stix Posted September 21, 2015 Author Posted September 21, 2015 (edited) Some results. I've tested a few small stars of each and the m.e.k. version definitely has less dross than the acetone - much better - If I had to guess, I would say 50% less. So that looks good at this point. What I haven't done yet is test in a star gun. Maybe the fuel will burn better given the extra oxygen. I'll do that test when I can. One other question is regarding the "skeletal" remains. When doing a static test, and others have also witnessed this, there is some sort of shell that is left unburnt. Perhaps that's the "dross" that I see falling - What is it? btw. These tests I've done uses a "flicking" apparatus allowing the stars to fall and burn through the air. Troy Fish recommends a 90:10 mixture of acetone:alcohol for wetting parlon stars. I suppose MEK would also work in this same manner. It's supposed to cut down the gooey stickiness and stringiness of solvent wetted parlon. . . . Does the alcohol help dissolve the red gum, or is it like expecting 10% water/alcohol to dissolve dextrin? Edited September 21, 2015 by stix
Mumbles Posted September 21, 2015 Posted September 21, 2015 Red gum is soluble in acetone, and presumably MEK as well, so any alcohol solubility is kind of a moot point. I'm not exactly sure how it works. My best guess is that it cuts down the solubility just a touch to prevent it from getting gooey.
rogeryermaw Posted September 21, 2015 Posted September 21, 2015 just replaced my supply of denat ETOH and acetone last evening so i'll test that probably tonight. the remains you see after combustion are the solid byproducts of the reaction. much like b.p. burns the carbon and makes CO and CO2 there are also solid products including possible sulfides, carbonates, sufates ect. i would expect that many of the star formulae using nitrates would do the same or similar. i have heard that many ammonium perchlorate comps do not produce ash or very little ash if the formula is well balanced.
rogeryermaw Posted September 22, 2015 Posted September 22, 2015 Just a quick first try but the 10% alcohol didn't cut down on the stringy mess while cutting.
Mumbles Posted September 22, 2015 Posted September 22, 2015 I'll go pull out my Pyrotechnica copy soon just to make sure I'm not remembering the suggested solvent combination incorrectly.
stix Posted September 22, 2015 Author Posted September 22, 2015 Red gum is soluble in acetone, and presumably MEK as well, so any alcohol solubility is kind of a moot point. I'm not exactly sure how it works. My best guess is that it cuts down the solubility just a touch to prevent it from getting gooey. Thanks Mumbles. Sorry about the dumb question - I should have already known that reg gum dissolves in acetone, as already I did this test in post #38. All the testing with different solvents is doing my head in a bit. Just a quick first try but the 10% alcohol didn't cut down on the stringy mess while cutting. The "stringy mess" phenomenon is interesting. I've read about it many times, but to date, I haven't experienced this. Weird. However, I've only done a few comps with parlon/acetone. The only time I experienced a stringy mess was when I did a straight parlon/acetone mix for testing purposes.
rogeryermaw Posted September 22, 2015 Posted September 22, 2015 the mess i experience is during the cut. even with a very sharp knife, pushed all the way through the comp and a slight sawing motion, i'll drag the knife to the left to move the cut strip away from the patty and there are webby strings of parlon between the strip and the patty. they don't separate cleanly. i have noticed that there is a short window of opportunity when the comp is still soft enough to cut without crumbling and dry enough to leave no strings.
stix Posted September 23, 2015 Author Posted September 23, 2015 the mess i experience is during the cut. even with a very sharp knife, pushed all the way through the comp and a slight sawing motion, i'll drag the knife to the left to move the cut strip away from the patty and there are webby strings of parlon between the strip and the patty. they don't separate cleanly. i have noticed that there is a short window of opportunity when the comp is still soft enough to cut without crumbling and dry enough to leave no strings. Ah, now I see - thanks for the explanation. Yeah it certainly is sticky. I cut them into strips first and leave it for 10mins or so then chop those up. The version I did with m.e.k. seemed to extend the "window of opportunity" a bit.
stix Posted September 24, 2015 Author Posted September 24, 2015 (edited) The dextrin/water comp stars have dried. It was certainly much easier to cut, but the downside being they take longer to dry (3 days). Although that doesn't really concern me as most of the charcoal based stars I've made are given 7 days. Anyway, the dextrin/water tests were comparable with the m.e.k. version, as in small amounts of orange slag. Both being much better than Acetone though. Whilst waiting for these to dry, I decided to make another comp (Light Green). GREEN STAR (ORIGINAL) GREEN STAR (LIGHT)56 Barium Nitrate 63 Barium Nitrate17 Magnalium 10 Magnalium17 Parlon 25 Parlon 7 Red gum 3 Red gum + MEK to form a pliable dough. As expected, the colour was much lighter, but this time absolutely no orange slag!! Also these stars burned from light green to a green/yellow just at the end - not too bad and very usable. I'm beginning to think that the orange slag is the skeletal remains burning off through the air. Well gentlemen (and ladies), It's time to face some harsh facts - I don't really know what I'm doing when it comes to coloured stars. I suppose one excuse would be that I don't have any per/chlorate, but the reality is that I don't understand what the particular chemical roles are in the formula, and then be able to adjust. Not so bad with the charcoal and glitter comps though. Also, maybe I'm being too picky. As was pointed out, large stars in a shell from a distance, and I would have been none the wiser, and never have seen the orange slag. I'm also not that naive to understand that I'll never get a nice "emerald green" with the chems I have, no matter how the ratios of the components are manipulated. I'd still like to improve on what I have, but I'm pretty much done with it. Afterall, this is just a means to an end. That end being launching some shells. I've got plenty enough usable 1/4" stars from the many tests I've done over this last year. Perhaps shell making might prove to be my forté? Cheers. Edited September 24, 2015 by stix
Arthur Posted September 24, 2015 Posted September 24, 2015 Work cold if you can! (keep the dough in a bag in a cool box with ice) Then the solvent is slower to evaporate.
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