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Author: Subject: Adding flame colorants to nitrocellulose

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[*] posted on 29-11-2017 at 22:22
Adding flame colorants to nitrocellulose

I’m wondering if this is possible and safe to do so (I have a fume hood with scrubbers with all PPE).

I would take cotton balls and let them soak in 70% nitric acid on an ice bath for a few hours (days? Not sure of the kinetics). After they finish nitrating, I would wash them with water while adding sodium bicarbonate. Always add acid to water so that means I’d dip the cotton ball into the water. Once they’re neutralized, I’ll wash it in distilled water to get rid of sodium. Then I’ll let them dry.

That’s a pretty standard DIY procedure for making nitrocellulose/guncotton from what I’ve seen on the net. Here’s my question.

Could I make saturated solutions of strontium nitrate and copper(II) sulfate? Then I could dip my nitrocellulose balls in these solutions and let them dry. My thinking is that the water would evaporate away, leaving a fine coat of flame colorant on the fibers. When I toss them into a fire, would the resulting fireball be colored by the strontium (red) or the copper(II) (green)? Or would the deflagration from the nitrocellulose overpower the color?

Also, would a different salt of strontium be better since I might be adding too much nitrate with strontium nitrate?

Most importantly, is this safe? Not just for me but for the environment as well.

[Edited on 30-11-2017 by azomage]

[Edited on 30-11-2017 by azomage]
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[*] posted on 30-11-2017 at 08:24

You'll need more than just 70% nitric, some conc sulphuric will be required too to dehydrate the NO3- to NO2+ (recheck the procedures you have read).
I used roughly 1:3 nitric / sulphuric mixed acid, pre-chilled and then cotton added carefully and left it to stand overnight. Neutralise well. Like REALLY well.

As for the colourant, it might work but I suspect the natural flame colour of the NC will overshadow any reds or blues you might see. Generally, you need the Chloride salt of the metal to be in the flame envelope in order to produce the colour.

I find it much easier to generate coloured flame in methanol - add a few percent boric acid to CH3OH and it will burn a lovely apple green, for example.


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[*] posted on 30-11-2017 at 09:15

I think you will have trouble getting a decent blue as is the trend with most pyrotechnics. It needs a cooler flame temperature which the NC I guess would not have.

I think red would be your best bet as it is quite strong emitter (SrNO3 maybe).
You might be able to get a distinguishable green too from barium compounds.

I got a decent red and green from strontium picrate and barium picrate in another thread here.

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[*] posted on 30-11-2017 at 20:47

this kind of thing isn't my strong point, so this is more of a question... What about the possibility of using colorful metal cations in soap form. Dissolved in alcohol and sprayed on the cotton leaving a waxy coating hopefully devoid of sodium yellow when burnt.

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[*] posted on 30-11-2017 at 21:26

Couple of thoughts.

I would not use a Sodium compound to neutralize the residual acid in nitrocellulose intended for a color other than yellow. Na is a very strong emmiter of yellow/orange, which will degrade or completely mask other colors. NC is notorious for the difficulty of washing out ocluded acid, why chance that it holds onto enough Na to be a problem too? Perhaps ammonia, used to neutralize the NC CAREFULLY, without overshooting.

The yellow color from burning pure NC may be at least partly from excess Carbon, it is about -20% Oxygen ballanced, give or take a bit depending on how thoroughly you have managed to nitrate the cellulose. So you might want to mix in sufficient additional oxidizer to take care of burning that Carbon to CO2. In particular, blue would probably turn out poorly with a yellow flame from excess C, it is always the dimmest color. Also, consider what Copper sulphate solutions might do to shelf life of NC, which does NOT like acidic things, and that every molecule of the sulphate will bring along up to 5 molecules of water to suck away the heat needed to drive the color emmiter- How about Cuprous chloride, Copper nitrate or perhaps Copper benzoate?

I have seen and used several proximate pyro manufacturers "low smoke" colored flame proximate devices based on NC. They usually have the typical smell of perchlorate compositions when burned- Suggesting that ammonium perchlorate might be used along with a colorant, or even that Strontium or Barium perchlorates might be used to kill 3 birds with 1 stone: Oxidizer, flame colorant and a source of chlorine to enhance the colors all from one ingredient.

The devices I have used and disected contained very finely divided cellulose mixed with some additional white powdered chemical, often some very fine metal particles (Magnalium?) were visible. The mixtures were pressed fairly lightly into their cardboard cases, no choke or nozzle used.

Personally, I have wondered about using Barium or Strontium peroxides for dual purpose oxidizer and colorant. Possibly with a bit of some organic chlorine donor- chlorinated isoprene, PVC, chlorowax, etc.

All of the above is speculation, I have not made such mixes, only used the finished devices.



Most importantly, is this safe? Not just for me but for the environment as well.

Well, if you read up on the nitrocellulose process a bit more, and have a hood and appropriate safety gear- Not terribly dangerous as energetic synthesis experiments go, but sure, you can always have an accident. Energetic accidents are usually memorable, unless they're just fatal...

Safe for the environment? Wouldn't worry too much if you know how to dispose properly of spent acid and are doing a few small test burns. Burning the product shouldn't be a terrible thing, but would best be done outdoors and down wind, especially for the Barium version.

[Edited on 1-12-2017 by Bert]

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[*] posted on 1-12-2017 at 02:45

I did some experiments long time ago, but what I did is dissolve NC in acetone and added colorants to the NC lacquer. I did one with strontium nitrate, but it was hydroscopic and when the aceton had evaporated - the piece was kind of wet and did not really burn. but flame was red when it did.

really nice result I got when I mixed Copper oxychloride in the lacquer, I did kind of filmed it, but only video I can give you now is this one :

camera did not quite get all the blue but it was really nice blue. (not completely pure blue tho.)

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