Linus1208
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Interesting white flare composition (Breslau Fire)
I found an interesting flare composition in a german youtube video:
https://www.youtube.com/watch?v=wlbXhuT3DRw
It's interesting because it uses Calcium sulfate (plaster of paris) as an oxidizing agent. The original recipe called for:
60% plaster of paris (CaSO4*0.5H2O)
20% Aluminium powder
20% Magnalium powder
It then is mixed with water just like you would do with normal plaster, but it shouldn't get to wet (the consistency should still be kind of crumbly).
I didn't have Magnalium powder so I changed it a bit to:
60% p.o.p
25% Aluminium powder
15% Magnesium powder
(I splitted the 20% MgAl to 10% Al and 10%Mg, but decided to use a bit more Mg as I didn't know if it would have a negative effect on the burning
properties).
I made a 75g batch of it (water taken into account) and filled it into a cardboard tube. I used a few sparkler granules to prime it, which worked
pretty well.
It burned very brightly, but it was gone pretty quickly for my taste.
Attachment: video0(1) (online-video-cutter.com).mp4 (7.1MB)
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katyushaslab
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Interesting, I recall doing something similar many years ago after seeing a post (I think by "Mr. Cool" on the now-defunct E&W forum).
~40% spherical aluminum, 60% plaster of paris, add water, and "cast" into cylinders then dry in an oven for quite a long time. Rather difficult to
ignite, but extremely bright/hot.
I'd worry somewhat about drying a composition with magnesium in the oven.
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Linus1208
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Quote: Originally posted by katyushaslab  |
~40% spherical aluminum, 60% plaster of paris, add water, and "cast" into cylinders then dry in an oven for quite a long time. Rather difficult to
ignite, but extremely bright/hot.
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I just tried it with just Aluminium, also works, but yes it is harder to ignite.
I used 27 parts of plaster of paris and 20 parts of aluminium (calculated for the dihydrate).
I put mine on the hot bed of my 3D printer, set at 80°C for it to solidify faster.
In case of an oven, you probably evaporate out the water to get the hemihydrate or even anhydrate of CaSO4. In my case I wanted the dihydrate, the
water will also react with the aluminium.
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Herr Haber
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Sooo...
Mg + 2H20 ---> Mg(OH)2 + H2
That's probably why they used magnalium...
The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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Linus1208
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I think it's
Mg + H2O --> MgO + H2
Mg(OH)2 will thermally decompose at temperatures greater than 350°C, which definetely are reached in this case.
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Morgan
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I remember molding some plaster of Paris mixed with magnesium powder and a bit of red iron oxide just for color. After wetting the mixture if I recall
it fizzed just a little and became quite warm as it was pressed into a small face mask mold.
I embedded some magnesium ribbon in the back of the mask to light it. The plaster mask hardened and came out of the mold nicely. When lit at night it
really lit up my backyard.
[Edited on 21-12-2021 by Morgan]
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Linus1208
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Got it to work with just Al
So I got the composition to work with just Al.
The stoichiometric ratio is 29parts of CaSO4*0.5H2O ("dry" plaster of paris), and 21 parts of Aluminium powder. For binding it add 10% of water (You
can use more, because it will be very dry and chunky with only 10%, just wait a bit longer for it to evaporate).
I can't remember how much exactly I used in the video, but it was around 20-25g.
I primed it with a bunch of sparkler granules, which barely worked as it was extremely hard to light, even heating it directly with a blowtorch for a
minute wouldnt light it.
Attachment: WhatsApp Video 2022-01-05 at 13.14.10.mp4 (2.6MB)
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Herr Haber
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I am pretty sure that if you add water to an Mg containing comp you will ruin it. That's the point I tried to make.
The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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Morgan
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I used magnesium with Plaster of Paris and it fizzed a little if I recall and then hardened nicely tamping down tiny bubbles a few times. It also
became warm. But it worked forming a hard substance.
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Fulmen
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Magnesium should be coated when used with water. IIRC linseed oil is considered sufficient for nitrates while perchlorates (and especially ammonium
perchlorate) require a dichromate coating.
We're not banging rocks together here. We know how to put a man back together.
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Linus1208
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Well it seams like it doesn't, at least not in this case.
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Morgan
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Here's a humble example of plaster and magnesium. On a previous attempt I think the torch preheated a chunk from the hardened mixture a little longer
and it made more of a whoomp or thud type sound and flash like in the old days with photography.
Dental Plaster of Paris and Magnesium Powder After Hardening
https://youtu.be/XKXy_KTtLDg
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metalresearcher
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Crushed drywall with Aluminum powder also works awesome.
Drywall is rather pure CaSO4.
I didn't try Mg powder with drywall.
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Morgan
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I was wondering what makes plaster dental plaster and came across something about set times that could be altered with different formulations. Also
this link if you scroll down, the page offers various kinds of plaster like molding plaster, pottery plaster, and others.
https://www.bestmaterials.com/detail.aspx?ID=25626
Below some characteristics of plaster and dental stone. Maybe bubbles would introduce a different kind of flame propagation with magnesium.
Manipulation of Dental Model Plaster
https://youtu.be/yn2rfgOrVs4
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Linus1208
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| Quote: Originally posted by Morgan |
Below some characteristics of plaster and dental stone. Maybe bubbles would introduce a different kind of flame propagation with magnesium.
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Hmm I might try granulating it, shouldn't be that hard to do with plaster.
Flame propagation needs hot gases, which wouldn't form with just CaSO4. But thinking about it twice it will harden by hydrating from the water you put
in, and the hydration water will form hydrogen when oxidizing Mg or Al.
If I remember correctly I could even hear a kind of "woosh" sound some gas flames make when burning large enough quantities of the plaster/Al mix. It
was probably the hydrogen burning of in the air.
[Edited on 27-1-2022 by Linus1208]
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