Potassiumchlorate Posted January 23, 2012 Posted January 23, 2012 Do you use the shellac as binder as well? That's my ideal, but I find it easier to use dextrin and water. Pinball prime with 5% silicon works fine for me. It might even work without silicon, but better waste a bit silicon for an overkill prime than having those beautiful and expensive stars blown blind.
Essohbe Posted January 23, 2012 Posted January 23, 2012 Do you use the shellac as binder as well? That's my ideal, but I find it easier to use dextrin and water. Yes, binder. If I use anything else it adds yellow-ish to it (so it seems).I will look into the silicone idea, sounds like a good one.
Potassiumchlorate Posted January 23, 2012 Posted January 23, 2012 I can't see that dextrin makes anything yellow, but of course, to get an über-pure flame one should have just the binary composition. Can shellac stand a really hard H3 burst?
Essohbe Posted January 24, 2012 Posted January 24, 2012 Well, the thing is they aren't the typical "stars" I'm making. The composition is loaded into a small payload tube that goes inside a 26mm munition shell. I haven't shot any yet because I broke the launcher (lol ) but I'm getting another soon. I know it will handle any lift within reason because of the payload tube but on it's own I can't tell ya. I'd expect it to break apart and if it did ignite send a mist of green fire everywhere. In a regular length payload the lift charge is about 30grains of 3Fg so that definately overkill for a tiny star. The shells will hold about 40gr and the heaviest payload tubes are the ones filled with gas/smoke mixes. I have to find the right amount of lift for the flare/stars because you want enough so that it burns out fast enough while still in the air. Too little and it will still be burning on the ground. You can accelarate the burn I'm sure but I don't want to add any more chemicals than I have to. The exact color I'm going for is that brilliant emerald color I get with straight shellac. Damn ass Barium chlorate is expensive too so getting the best color I want with the least amount of Barium salt makes sense to just use less instead of trying to make a giant star and excelerate it's burn.
Potassiumchlorate Posted January 24, 2012 Posted January 24, 2012 I think the solution for an "ordinary" shell is to simply make smaller stars. Saves a bit of money too. I had 20mm stars in my 6" shells, but I think 15mm would be better or even 12.
Peret Posted January 25, 2012 Posted January 25, 2012 (edited) There's an interesting corollary to my shellac experience. I decided it might be a good idea to make up a shellac solution in alcohol, so I added about 15 grams to 150 grams of denatured. It refused to dissolve. A week later, what looked like the whole of the original quantity had settled out in the bottom of the container, with a cloudy brown liquid above. I tried to filter it to weigh the residue but it clogged the filter and wouldn't run through. The liquor didn't seem sticky at all, though as the alcohol evaporated it left a thin sticky film. This wasn't anything like what I expected. Lancaster writes that natural shellac can be separated into two resins, "soft" lac 30% and "insoluble hard" lac 70%, but I didn't take the "insoluble" part seriously, since everything else I've read says it dissolves in alcohol and I was expecting a clear varnish. Edited January 25, 2012 by Peret
Potassiumchlorate Posted January 25, 2012 Posted January 25, 2012 Haha, I did the same. I used flake shellac from a hardware store. Same result.
drthrust Posted January 25, 2012 Posted January 25, 2012 thats interesting about the soft and hard shellac, it may or may not of answered a question ive pondered on for a good while.. in Weingarts book theres a yellow fire formula that calls for " sheel-lac" it appears a few time in his book along side shellac, i couldn't make up my mind what it was, possibly its describing the hard shellac ?
Potassiumchlorate Posted January 25, 2012 Posted January 25, 2012 You are correct: How shellac is made
Potassiumchlorate Posted January 27, 2012 Posted January 27, 2012 (edited) By the way: it seems that barium chlorate/shellac burns a bit faster and clearer with SGRS as the binder than with dextrin. Unfortunately I still haven't learned to pump SGRS bound stars. Now they become rock hard when dried, but they tend to either not adhere or to stick to the pump by the actual pumping. Update: very nice surprise: with SGRS as the binder the stars seem to burn much faster than with dextrin. Edited January 27, 2012 by Potassiumchlorate
Essohbe Posted January 27, 2012 Posted January 27, 2012 I decided it might be a good idea to make up a shellac solution in alcohol, so I added about 15 grams to 150 grams of denatured. It refused to dissolve. I go to the hardware store and simply get the liquid shellac in the tiny cans. It comes dissolved already in a mix of methyl and isopropyl alcohols if I'm not mistaken.
Potassiumchlorate Posted January 28, 2012 Posted January 28, 2012 I made a few test stars again with shellac as the binder and isopropanol as the solvent. Pumped stars become a little brittle at the edges, but otherwise they seem pretty strong. It's hard to use the exact amount of isopropanol, though. Too little and they will not adhere. Too much and the alcohol will be trapped in the stars.
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