Can i use finer mesh Aluminum in this formula ?
Posted 30 April 2017 - 12:56 PM
I made the same formula three times, with three different aluminums, and got three results.. Unfortunately only one video
Posted 30 April 2017 - 01:23 PM
First off, I'm going to move this to a different section since it seems this conversation is going to continue. The original section is really more of a database for tried and true compositions, and not general questions and discussion anyway.
David, bringing up the off-board reactions brings up an important point I feel that is going to underlie this conversation. I was having a conversation with Maserface the other day about this. To me, there is a subtle functional difference between a true glitter and something like a firefly, brocade, certain streamers with delayed metal ignition, etc. Just for simplicity, I'm going to call the latter the firefly effect for the purpose of this discussion They often can resemble each other, and probably can both manifest themselves in the same comet. Glitters are believed to function by a sulfide melt being formed in the comet, coating the metal particles, and being blown off the surface. After some delay through the air the sulfide is oxidized to sulfate, at some threshold of reaction and temperature, the particle explodes in a flash of light. Fireflies and other delayed ignition stars probably function on a similar principle, however the functional difference is that they rely on atmospheric oxygen to complete combustion of the metallic particles. Whether this is purely due to larger metal particle size or combined with somewhat different formula requirements can be discussed. The telling evidence that there is a difference between these two is that you can make the firefly type effect happen with Ti and FeTi, whereas to the best of my knowledge they do not work in true glitters.
The real breaking glass effect is probably a mixture of both of these. The dripping appears to be slightly delayed, and the is clearly not a flash like you see with glitters, though there is some of that in the tail.
While I haven't felt the need to join in, I have been following this thread and thinking about the things discussed. I looked through a bunch of formulas to see if there were any trends or rules that might pop out. I went at it from the view point of sulfur makes a formula glitter, delay agents just modify them or makes them better, not makes or breaks the effect. A bad glitter still glitters. It might be worth noting that barium nitrate acts as both an oxidizer and a delay agent. It gets a little complicated trying to account for both sulfur and antimony trisulfide. Win39 tells us that Sb2S3 alone is sufficient. Most glitters had at least 16% total sulfur content (just S + Sb2S3), though that varied up to over 20% to down to 10-12%. Winokur 11 is one the lowest I found, which has 10% sulfur, though also contains a healthy amount of barium nitrate, and 1% iron oxide. Winokur 12 has low levels of both sulfur (8%) and antimony trisulfide (5%). Winokur 31-38 also show low levels of total sulfur with different additives. 10-12% is probably the lower limit of functionality.
Conversely, firefly effects require less. Rarely do they use over 10% sulfur actually. They're typically all sulfur, and tend to be in the 6-10% range. Larger particles have less surface area, so it could be argued that they need less sulfide melt. Since atmospheric oxygen may be required to complete the combustion you also don't need enough melt to totally consume the particle, just ignite it after a delay. The reason is up in the air, but the amount of sulfur certainly appears to be lower. It is worth noting that the collection of these sorts of formulae is much smaller than for glitters.
For what it's worth, I took Maserface's comment to mean that he's using the real breaking glass base formula. It clearly works with a finer aluminum, though without the characteristic drip. Ned's formula resembles the effect, though not nearly as drippy. It might just be the Al used of course, but could also be two different ways/formulas to achieve a similar effect. More than one way to skin a cat. I included videos of both below.
Real Breaking Glass:
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Posted 30 April 2017 - 01:55 PM
Thanks Mumbles, that was very informative. I wonder if- for pyro purposes- granular aluminum must be atomized spheroidal. It would be easy enough to make some raspings in the particle sizes quoted, if the angular shape didn't matter too much.
EDIT: JHere's Ned's palm tree shell with titanium . The titanium falls just like the aluminum in Ace's comets, but definitely lacks the 'drippiness'.
Edited by DavidF, 30 April 2017 - 02:00 PM.
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Posted 30 April 2017 - 07:09 PM
In answer to that last, I can give you something definitive, instead of just a guess.
We were bequeathed somehow a 100lb drum of 80-mesh truly granular aluminum which was obviously made by some machining or 'rasping' process.
The particles were not long shavings, but small irregular particles with visibly 'cut' edges all-around, and roughly as long (maybe up to 1-1/2x the length) as their narrower middle dimension. They often had angular 'sharp' ends or corners, just as you'd expect a machined particle to have.
It worked fine in non-glitter 'tail' effects, and I tried it once in a slow sulfide glitter. It was too slow, with the flashes too large, too sparse, too far behind the head, and accompanied by a flitter tail, also; but it did glitter.
Edited by lloyd, 30 April 2017 - 07:10 PM.
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