4 replies to this topic

[deepakpyro]

Hello,

 

I am armature in the pyrotechnics.

started to make some star in small batches less than 80 gms (enough for 2/3 inch shell).

list of metallic powder currently i am using are

1. Manganalium (200 mesh)

2. Aluminum powder (200 mesh & 325 mesh - Spherical)

3. Aluminum powder (flake - grade MEPCO 666,333,999).

 

i have read in many topics about the incompatible mix of Nitrates and Aluminum powders. 

 

when ever i am making stars composition only having the Al powder + other stuffs, i am adding 1% - 2% Boric acid to stabilize the formula. 

 

But, currently i need to make some color stars which i need to mix MgAl and AL. 

 

i am afraid of ignition of composition due to non-compatible properties(presence of Al) . 

 

does adding boric acid solve my issue also here ?. or Boric acid will have reverse reaction with MgAl making it unstable ?.

 

if i need to roll my stars is that will be a problem ?, where i am using 75/25 water/IPA 

 

Any safety tips i needed for storage of finished shell. 

 

Better safe rather than sorry.

 

Critic/answers/advises/thoughts most welcome..... 

Edited by deepakpyro, 16 February 2021 - 12:05 PM.

[SharkWhisperer]

Hello,

 

I am armature in the pyrotechnics.

started to make some star in small batches less than 80 gms (enough for 2/3 inch shell).

list of metallic powder currently i am using are

1. Manganalium (200 mesh)

2. Aluminum powder (200 mesh & 325 mesh - Spherical)

3. Aluminum powder (flake - grade MEPCO 666,333,999).

 

i have read in many topics about the incompatible mix of Nitrates and Aluminum powders. 

 

when ever i am making stars composition only having the Al powder + other stuffs, i am adding 1% - 2% Boric acid to stabilize the formula. 

 

But, currently i need to make some color stars which i need to mix MgAl and AL. 

 

i am afraid of ignition of composition due to non-compatible properties(presence of Al) . 

 

does adding boric acid solve my issue also here ?. or Boric acid will have reverse reaction with MgAl making it unstable ?.

 

if i need to roll my stars is that will be a problem ?, where i am using 75/25 water/IPA 

 

Any safety tips i needed for storage of finished shell. 

 

Better safe rather than sorry.

 

Critic/answers/advises/thoughts most welcome..... 

Deepak hi,

 

Although many use boric acid in Al/nitrate mixes (and I used to) I have never had an issue where I thought it was necessary. Others have, though. If adding boric acid, it's usually best to dissolve it first into any water that you are using to moisten your star mix, to assure uniform distribution. It is not very soluble, but you can get enough into solution. When I used it, I only used 0.5% final composition mass of boric acid--not 1 or 2%. If you have composition warming issues with Al/nitrates, then boric acid can be useful; I've just never experienced that. My pound of boric acid (454g) still contains 444g, after 5 years!! But it will not hurt anything to include it, and if it makes you more comfortable than please do so. Me? I'd rather have one less chem to weigh and incorporate into my comps...

 

I also do not worry about nitrate/MgAl mixtures, and do not add boric acid to those, either.

 

Many star comps contain both MgAl and Al without any problems.

[deepakpyro]

Hey sharkwhisper,

Its great to hear from you again.
My doubt is comps having nitrate+MgAl+Al flakes.
Worried about that only.

I will start with less amount.
Lets check out it by week drying time.

Edited by deepakpyro, 16 February 2021 - 09:16 PM.

[Richtee]

Huh...finally a use for all those lousy IPA’s out these days

 

(OK the poster is obviously not from America... It’s a joke. And, an explanation. IPA is a beer style, and not a well conceived one in my opinion. But it’s all the rage with the kiddies these days. Prolly WILL remove the Tide Pod taste from yer mouth tho. Maybe that’s the deal)

Edited by Richtee, 16 February 2021 - 01:50 PM.

[SharkWhisperer]

Hey sharkwhisper,

Its great to hear from you again.
My doubt is comps having nitrate+MgAl+Al flakes.
Worried about that only.

I will start with less amount.
Lets check out it by week drying time.

Deepak, I recalled something that Mumbles wrote in a different thread about boric acid potentially reacting with MgAl:

 

"I typically just add boric acid to the wetting water.  You can only get maybe 3-4 wt% to dissolve normally, even though it has a higher reported solubility in some places.  It's much more effective at buffering when it's in solution.  The Nitrate/Al reaction is mediated by water, so it wont really happen once a composition is dried anyway.  I've only had an issue with a few select compositions, and they all contain additional basic components like sodium oxalate or sodium bicarbonate.  They usually were based on flake Aluminum as well.  Boric acid really doesn't affect the burn rate noticeably, and certainly not the color.

 

Boric acid does react with MgAl.  This, like all reactions, is even worse if heated.  Boric acid works by soaking up hydroxide to make borates.  This is how it mediates the nitrate/Al reaction.  The same property can cause it to react with MgAl.  Aluminum oxide itself is somewhat amphoteric due to how much it likes to hold onto it's oxygen.  It is decently acidic which allows hydroxide to easily attack and makes aluminates, which expose fresh Aluminum and can continue to react.  However, this oxide layer tends to be fairly inert to weak acids since it does not necessarily want to give up it's oxygen.  You need something fairly strong to dissolve it.  Magnesium is not the same.  It is also amphoteric to some degree, but it's oxide layer is both flakier and more basic.  This makes it more prone to reacting with acids or water.  It is this property that makes MgAl more prone to attack or will allow boric acid to dissolve it's oxide layer.  MgAl is more prone to react than aluminum, but less so than pure magnesium."

 

So, you might be better off just leaving the boric acid out of your mix containing both MgAl and Al together. Use boric acid only for nitrate comps containing Al as the only metal, if at all...

Edited by SharkWhisperer, 18 February 2021 - 08:32 PM.