chemball Posted December 10, 2014 Posted December 10, 2014 (edited) Hello all, I am relatively new to the hobby and i was making a batch of tiger tail stars and i thought i might add some 325 mesh aluminum to the comp. I added about 5% to the comp, but i forgot about the incompatibility between the potassium nitrate and aluminum. My question is that I do not have boric acid, so should i burn the comp? Is it dangerous in its current state? Edited December 10, 2014 by chemball
Sparx88 Posted December 10, 2014 Posted December 10, 2014 (edited) If they are already dry and don't smell like hot sulfur they are good to go. It's during the time they are wetted you have to worry. Using really fine aluminum 500 mesh and up raises the odds of a reaction. Walmart has boric acid cheap where the roach sprays are at. 4$ for the pound. ENOZ Roach Away Boric Acid. Most people agree that 2% in a 100 gram batch is good. Add it before you start working the patty to get it mixed in well. Some add it to the water/alcohol solution to dissolve it that way. Edited December 10, 2014 by Sparx88
chemball Posted December 10, 2014 Author Posted December 10, 2014 currently the mixture is in powder form, i have not made the cut stars yet. Is the comp safe to sit overnight? Am I in any immediate danger? I will go buy the boric acid tomorrow after work and then make the cut stars.
OblivionFall Posted December 10, 2014 Posted December 10, 2014 Could someone please explain to me how potassium nitrate and aluminum are incompatible and what things you cannot make because of this?
nater Posted December 10, 2014 Posted December 10, 2014 (edited) The only danger is when the comp is wet with water. The dry comp is as safe as any flammable composition. Someone else will have to explain the exact chemistry here. When fine aluminum and potassium nitrate are in the same comp and when it is dampened with water, it has the potential for a run away exothermic reaction which can end in the composition igniting. Pumped stars contain much less water and are not as suceptible to this reaction. Many pyros never see this reaction occur. Boric acid added to the water before wetting the comp helps prevent it. It is also wise to dry the stars in the shade and away from anything that could be harmed if they do ignite. (Which is wise no matter what you are making.) Edited December 10, 2014 by nater
ddewees Posted December 10, 2014 Posted December 10, 2014 (edited) Someone once said they dissolve boric acid in their jug of distilled water they always use... some small amount. Can't remember who, or how much... but it was minimal. Edit:http://www.skylighter.com/fireworks/how-to/protect-aluminum-powder.asp Edited December 10, 2014 by ddewees
Mumbles Posted December 10, 2014 Posted December 10, 2014 As long as it's dry you're fine. I can explain the chemistry later, but you're fine for a while. Things are the worst when wet and confined in a large mass, specifically with oxalates or bicarbonates around. Flake Al is much worse than atomized as well. Since you don't have anything basic (bicarbonates or oxalates) around, and you are using atomized Al you'll most likely be fine even if you do wet it and form it into stars. I generally don't bother with boric acid unless it's likely necessary, such as flake Al combined with basic components.
zakmaster524 Posted December 11, 2014 Posted December 11, 2014 i know you have probably purchased boric acid but to answer your question, buy the boric acid ASAP unless you already have.
LiamPyro Posted December 11, 2014 Posted December 11, 2014 Flake Al is much worse than atomized as well. I'm pretty sure I'm wrong, but with a common flake aluminum such as bright flake, wouldn't unwanted reactions with nitrates be considerably less of a concern because of the stearin coating? Atomized aluminum is usually uncoated, so it seems it would be more susceptible to these kinds of issues. 1
LiamPyro Posted December 11, 2014 Posted December 11, 2014 Then again, atomized aluminum is generally harder to ignite and the particle shape causes it to have less surface area per amount of aluminum (less immediate surface area to be reacted with), so your probably right... 1
Carbon796 Posted December 12, 2014 Posted December 12, 2014 Not all bright flake aluminums are coated.
enanthate Posted December 28, 2014 Posted December 28, 2014 Hey guys,I just assembled a 6" with slowflash using flake al, first time I have used flake and all I know is that the mixture gets more sensitive for moisture when using flake. Started pasting, and after only a minute I noticed that one small area of the shell felt warm. Not very warm, but I'm quite sure my hands didn't do it. It's now placed outside in -10C, cooling off just in case. Am I paranoid or could this happen? Perhaps its not that uncommon? Just wanted to check with you guys.
Col Posted December 28, 2014 Posted December 28, 2014 likely paranoia, unless something inside the shell is wet which it shoudnt be
enanthate Posted December 28, 2014 Posted December 28, 2014 Well... Yeah it was.Had 10mm between the two hemis, and being at the point of no return i had to ram them together. Had a couple of mm air around the equator. Add wet gumpaper to that, and wollah. Likely paranoia tho, like you said. Got two layers on it now, and im still around!
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