KNO3 ph in charcoal comps

[Merlin]

I am trying to make "firefly" stars. They are currently drying. I have read that potassium nitrate with a low ph will cause problems with the firefly effect. My question is what difference does ph make? Mine may not work at all as I added boric acid because of the aluminum. They are 1/2" stars and have been in 130 degree F drying box for 24 hours and will still crush between the fingers.

Is the addition of boric acid appropriate for firefly and about how long to dry this type of comp? I think I already know the answer but if one added firefly aluminum to a color comp could you still expect flashes?

[OldMarine]

I've read that those comps take a very long time to dry and should be air dried for the first few days before applying heat. I just acquired the aluminum to make these myself so I am as eager as you to know the answer!

I have no idea as to the effect the boric acid might have on the comp.

[dynomike1]

I dont see where Firefly calls for Boric Acid. Did you cut roll pump?

[OldMarine]

I dont see where Firefly calls for Boric Acid. Did you cut roll pump?

It doesn't call for it but he added it out of fear of a reaction in the comp.

[lloyd]

The boric acid would not ordinarily affect the composition adversely, and could improve things. Give it more (and gentle) drying.

 

Oh... and ensure you actually used a binder in the mixture! <grin> (it's been forgotten before!)

 

Lloyd

[Merlin]

They are cut. The formula did not call for boric but I have read of some exothermic reactions that can occur when wet so I added boric as a precaution. Oops. I forgot the long slow drying for this type comp. I am so used to making color comps. I may well have ruined this batch by putting them in the drying box. I know I added dextrin but they are not likely dry in 24 hours- the outside is hard but the inside is soft.

Edited February 18, 2017 by Merlin

[braddsn]

Merlin.... the situation that you are experiencing now.... I have been through it about 10 times, and that's how many times it took me to finally learn my lesson!! LOL. Firefly, or specifically, charcoal comps with aluminum (not sure if the aluminum has anything to do with it) take FOREVER to dry, and specifically when they are CUT. I do cut some stars, (very few, and only when I absolutely have to), and when I cut these comps, they can take weeks to dry. I usually let them air dry for a week or 2 (depending on humidity outside) then throw em in the dehydrator. Then, in the dehydrator, they soften up after a few hours and seem like they are ruined. However, 24 hours later in the dehydrator and they are rock hard. Take your time with them. I will say that when I roll stars like this (I rolled some firefly last week), they dry in days instead of weeks. I prefer rolling over other methods, and this is just one of the reasons.

 

Another mistake I have been making, and I am slowly getting better at it.... is using TOO MUCH water/alcohol. Use as little water as possible to be able to make a patty and cut them. I am still no expert, but the less water you use, obviously the less of this drying problem you will encounter.

 

Oh and 1 more thing.... and don't ask me why this is, (maybe Mumbles or Lloyd can comment), but I have noticed something interesting. Once I throw them in the dehydrator for a few hours, they obviously get very hot, and they almost swell a little and get mushy. But amazingly, I then shut the dehydrator off, and when they cool, (takes about 5 minutes) they become rock hard. So strange. Almost like the heat was keeping them soft. Then once they cool, I turn dehydrator back on. I repeat this process a few times until they are finally completely dry. Pyro is weird sometimes, some things I can't explain. haha.

[Merlin]

Thanks Brad! Lot of good information! I haven't worked a lot with these type comps. ( Always concerned about fallout). I will continue drying and start some winokur 37 or 40.

Thanks much!

[OldMarine]

I love the Win 37. 1½" comets from a consumer mortar are awesome! Even better with some crackle added in. We fired a battery of them from my boss' boat dock and the reflection from the water doubled the effect.

[DavidF]

They get soft when you add the heat because potassium nitrate is waaay more soluble in hot water than in cold water. The cut stars have a lot of water. If you take freshly cut charcoal-type stars that have been overwetted and put them in the hot sun, they will melt! Ask me how I know

[lloyd]

BTW... you mentioned that you "may have ruined them..." by causing them to be 'driven in'. That's the bane of 'wet' star-makers, and most think it's ruinous.

 

But, unless the composition has undergone decomposition, a driven-in condition can be reversed by placing the stars in a very humid environment (say a sealed plastic bag) until the outer hardened layer softens again. Then, place them in a slow, temperate drying environment, and they will continue from that stage, as if never driven-in.

 

In commercial manufacture - and especially with deadlines - losing a large batch of stars to such an event could cause you to lose a contract. So, we experimented with ways to salvage them. Despite common opinion, it works just fine on a comp that doesn't decompose from having been wet too long.

 

Lloyd

[Merlin]

Thanks Lloyd! I will do as you suggest. It's easy to see the potential disaster on a industrial scale. Maybe they will turn out. Plenty of time to dry them. How are you folks feeling about this year? It's 78 in February and still behind on total rainfall here. By August last year we had a ban on fireworks. I am hoping for "Green" grass for the 4th.

[lloyd]

Merlin,

We had a gentle drizzle all night, which at least somewhat mitigated the fire danger here on the farm (all pasture, but dead and dry right now).

 

But last week, we had a nearly square-mile fire not 2 miles from my house. Only the prevailing winds kept it from coming here.

 

So... I expect Florida will do what Florida does. It's always dry in the Winter, and gets damp in late spring. I hope.

 

Lloyd

[Mumbles]

To answer your original question, the pH mitigates the reaction between nitrate and aluminum. It needs base (hydroxide) to work, and the more of it the faster it goes. The same is true of temperature. Higher temperatures accelerate the reaction as well. Aluminum usually forms a thin protective oxide coating, however with a high enough pH this can be dissolved. Aluminum metal is actually quite reactive, but the oxide layer usually mitigates this reactivity. With the oxide layer getting dissolved, the metal is allowed to react unrestrained. Boric acid helps to neutralize the composition by soaking up hydroxide ions and prevent reactions.

 

Firefly aluminum is quite coarse and not usually subject to adverse reactions. Fine flake Al is the worst in my experience. Boric acid wont hurt the composition though. It can react with magnesium however, so I never use it with MgAl compositions. I don't necessarily think you've ruined this batch though. Firefly Al is really not very susceptible to reactions and there is boric acid around anyway. If the stars don't have an ammonia or rotten egg odor, you're most likely fine.

 

I always let compositions like this dry for a while at ambient conditions often with a fan to improve airflow. I don't really like heating glitters or nitrate/Al compositions if I can help it.

[Merlin]

Thanks to everyone for your help. I think I'm OK as this was actual firefly aluminum. I will allow the winokur 37 to dry fully at ambient temp.

Good luck everyone in southeast this year. The weather pattern worries me. Nothing we can do about it! Ironically I truly am fearful of a wildfire!