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Is it really necessary to coat magnalium stars?


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#21 NeighborJ

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Posted 17 October 2017 - 09:48 AM

Green light, yes I agree that boric acid should not be used with magnesium BUT this is MgAl which is a lot less reactive to ph imbalances. I found a brand new formula yesterday which was added to the fireworking.com database which uses boric acid and MgAl. Unfortunately there seems to be some sort of a problem accessing the site today, I will post the example as soon as this problem is resolved.

I have personally had an example of needing to add boric acid to a MgAl comp to prevent a reaction. The comp I used it in was pyrotex' s sodium nitrate glitter. I had a reaction which caused the stars to crumble into dust, I traced the issue to the charcoal which I picked (oak) which turned out to have an extremely high ph. I added boric acid to the next batch and the issue went away.

This may not be a typical use of this combo of chems but it may be the reasoning behind its appearance in many comps. Many charcoal tend to become quite basic and the acid is likely added as a preventative measure, (just a theory).

Ok an update, I've found the new formula in question. Independence white strobe star: KNO3-52.4, MgAl-20, BaNO3-9.5, sulfur-8.6, Boric acid-4.7, dextrin-4.8

This formula does not support my theory of charcoal PH balance due to the lack of charcoal so there must be some other reason for its use.

Edited by NeighborJ, 17 October 2017 - 10:03 AM.


#22 Mumbles

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Posted 17 October 2017 - 11:23 AM

Just because it's included, doesn't necessarily mean its 1) Necessary or 2) A good formula.  I've seen a lot of instances where it's included just out of habit because manufacturing firm X used it in all their glitters and streamers when they were based on aluminum.  Why not add it to MgAl glitters too, or strobes, etc.  I think the reality that boric acid is incompatible with MgAl is only more recently becoming common knowledge.

 

I've certainly added it to plenty of MgAl glitters in my time without too much of an issue.  In my experience, the only time it has really destroyed the effect is if the star is heated.  Many reactions accelerate at elevated temperatures.  


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#23 greenlight

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Posted 17 October 2017 - 11:50 AM

NeighborJ, I only stated that boric acid should not be used with magnesium because the formulas he listed contained the two together and I know the Mg would be attacked..

I am unsure on the degree of instability when using boric acid and MgAl as I have never used compositions with the two together so I have no real input on that apart from my reading that they shouldn't be mixed.

#24 redbullzuiper

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Posted 17 October 2017 - 02:23 PM

I found these formula's on http://creagan.net/f...mpositions.html

 

Seems like a very helpfull website for any pyro hobbyist.



#25 Sulphurstan

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Posted 17 October 2017 - 02:27 PM

If you have FAST, have a look to table 12. In my point of vie, Prof Shimizu is probably in the top five of 20th century fireworking, he made extensive scientific research about FW. And his table 12 is mentioning the action of h3bo3 on MgAl.

Edited by Sulphurstan, 17 October 2017 - 02:29 PM.





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