823 replies to this topic

[BrightStar]

Inspired by Karl's recent, excellent Maltese Beraq tutorial, I have been trying out some of the coloured flash mixes. A hint - they are very bright indeed!

I'm interested though that some of the mixes, the red 1 Mg + 1 Sr(NO3)2 + 0.1 PVC for example, seem to be quite under-oxidised (57% of the required oxygen) compared with traditional 70/30 Perc/Al (120%) or the brighter 60/40 Perc/Al (78%).

I'm working on the assumption that:

Sr(NO3)2 + 5Mg -> SrO + N2 + 5(MgO)

211.6 + (5*24.3) -> 103.6 + (2*14) + (5*40.3)

ie the optimum ratio Sr(NO3)2 to Mg is 1.74:1, not 1:1 as in the above forumla.

Is this correct? Does the surrounding air supply the missing O2? It seems quite common to reduce the oxidiser ratios for Mg based flash and flare compositions, but I'm never quite sure why. Any thoughts?

Edited by BrightStar, 07 October 2006 - 05:15 AM.

[BrightStar]

Just a quick test report that the following red flash (my own formula...) works well:

Strontium nitrate: 55
Potassium perchlorate: 10
Magnalium (fine flake): 35

Grind the Sr(NO3)2 and KClO4 together as fine as possible with a pestle and mortar, then diaper in (do not screen - see below) the magnalium.

A couple of grams twisted into tissue paper will report, 5g in a 3/4" id thick-wall tube about 1.5" long will make a very impressive shell insert. A small percentage of Parlon might deepen the colour.

Edited by BrightStar, 10 October 2006 - 02:37 PM.

[karlfoxman]

Did you say screen in the mg/al?!? Im sorry but you never ever screen a flash composition! Treat this as a warning, never ever use a screen in flash! The only way is diaper method. Please use diaper in future, wish you all the best with colour flash, post any vids you have. Dont take this the wrong way but please dont screen flash compositions.

Ill try this at some point, was it red deep?

[BrightStar]

Thanks Karl My apologies, as you spotted, it was a typo on my part, rushing to post before dinner. I would never take this composition anywhere near a screen... My small test batch was mixed on paper then handled with plastic implements.

The intention was to create a red flash that avoids the need for messing about treating fine magnesium powder with dichromate etc. and avoiding chlorates. The colour is usable at present, but could be better. As I improve it, I'll post the results here.

As an additional safety measure, I installed a thermo-hygrometer in the workshop and will only do this work in high humidity. Will post details in the tools section...

Edited by BrightStar, 09 October 2006 - 02:02 AM.

[karlfoxman]

Thats good to hear, diaper is the one and only way if you have to make the stuff. Ill be making another maltese beraq shell at some point, it seems quite hard to get a good colour with the flash mixtures. I think its mainly the type of magnesium you use. I managed to get some magnesium flake and it makes one hell of a change. Be good to see your results.

Edited by karlfoxman, 08 October 2006 - 07:42 PM.

[pyrotrev]

Sounds impressive guys - wish I had some MgAl flake! Methinks adding a chlorine donor definitely ought to be good for deepening the colour, since MgO has a very strong continuous (e.g. white-ish) emission spectrum, whereas MgCl doesn't.

Edited by pyrotrev, 08 October 2006 - 07:54 PM.

[BrightStar]

Sounds impressive guys - wish I had some MgAl flake! Methinks adding a chlorine donor definitely ought to be good for deepening the colour, since MgO has a very strong continuous (e.g. white-ish) emission spectrum, whereas MgCl doesn't.

Pyrotrev: That's interesting, that the chlorine might actually darken the white glow, as well as brightening the red SrCl spectra. My thinking on adding the potassium perc had been to boost the oxidation power of the strontium nitrate, which is a bit lackluster with slower fuels and also to release a bit of Cl+. I'll try with the Parlon as discussed to enhance this.

Karl: Interesting that the magnesium type makes such a difference. I recently found a supplier (very expensive though) for small quantities of 300-mesh atomised magnesium so might give this a go to compare. In the tests some of the slower burning comps with larger mesh metals seemed to give better colours, to the detriment of brissance.

Replacing some of the Mg/Al with a darker fuel (maybe potassium benzoate) might also be interesting - less white, the same red strontium glow and just as much 'bang'...

Edited by BrightStar, 11 October 2006 - 06:49 AM.

[al93535]

I would just like to add. Why even use perc? Nitrates and mg or mgal will do just fine for the purpose of making a colored report. The KClO4 is just making it more sensitive, and thus more dangerous to work with. Perc hardly adds much chlorine. Stick to nitrates, and add a small percentage of chlorine donor.

I have seen 13 micron Mg, saran, and Sr(no3)2 make quite a large report in small quanities with minimal confinement with good color.

Just my two cents

[BrightStar]

I would just like to add. Why even use perc? Nitrates and mg or mgal will do just fine for the purpose of making a colored report. The KClO4 is just making it more sensitive, and thus more dangerous to work with. Perc hardly adds much chlorine. Stick to nitrates, and add a small percentage of chlorine donor.

Well, IMHO, since perc gives so much more oxygen per gram than nitrates, adding a bit gives you more flexibility in the formulation, while adding a bit of Cl+.

Perc begins to thermally decompose at about 570 degrees (see The fusion point and thermal decomposition of KClO4), whereas strontium nitrate decomposes at about 500 degrees.

The lower decomposition temp of the nitrates along with the general reactivity of Mg are reasons to consider the coloured flash formulae to be more hazardous than, for example 70/30 Perc/Al. I believe that adding perc will give a more powerful flash allowing scope for more additives, but should not increase thermal sensitivity.

As I say, this is mostly just my current opinion ... and let's not even consider the traditional Maltese chlorate mixes...

Edited by BrightStar, 11 October 2006 - 10:45 AM.

[karlfoxman]

Yes dangerous but very very good colour from them, the red is ruby red and the green is emerald green. I have seen blue reports if you like to play with paris green!

I have tried your formula for the red flash and seems almost identical to my Stontium nitrate 50 magnesium 50 + 0.5 saran resin. Parlon would work too I guess but the colours still seem washed out, maybe confined they will start to work and give better red. If the formula gets too slow the reports could starts to 'jet' instead of report. I have seen some maltese beraq jet before. Somewhere I do have an original formula for the maltese beraq, ill have to ask permission to publish them but I feel they are way too secret.

[ibah]

Hi I am new to this site and was wondering about this aluminum powder I have recently bought. Here are some specs on the Aluminum powder - 1250 mesh - Reagent Grade 99.99%, Super fine 10 micron, spherically atomized, reactive, uncoated powder. The reason I am asking is that when I tried to make some flash the way I always have, it was very hard to light and when it did light it burned slowly and just turns into a blob of very hot molten metal which is quite bright as it burns. I have been trying the aluminum with potassium nitrate and have tried potassium perchlorate in 10 gram trials and still can t get a good flash. Is there other formulas I can use to make flash with this aluminum powder.
I have made flash with other aluminum powder and have had no problems with it. Also would 200 mesh aluminum be used for flash. Any answers are greatly appreciated.

[rocket]

The reason your flash is so bad is that the AL is spherical in shape. Where did you get the Al, if you got it from ebay it might not be the mesh they stated. 200 mesh Al is no good for flash.
And if your new to pyro you shouldn’t be make flash anyways.

[karlfoxman]

Shudder! Shudder! This sort of talk scares me, how are you mixing your aluminium/oxidizer?

[ibah]

Hi again mixing it 7grams oxidizer and 3 grams aluminum. Thanxs for the replies.

[karlfoxman]

What method for mixing?? What are you using tool wise?