smoke grenade problem

[ghost]

Here's my best smoke comp so far:

 

43% Zinc Oxide

43% Hexachloroethane

14% Aluminum (atomized)

 

I'm housing it in 1" ID, 1/8" walled parallel wound tubes, however, when the mix is ignited, it produces a sizable 1 1/2 - 2" high temp flame out of the top, no matter how far I recess the mix in the tube? Is there a way to arrest these flames? (i.e. just have smoke come out instead of FIRE?)

 

Comp produces EXCELLENT grey/white smoke btw.

 

PS mix is somewhat hard to ignite if you want to try it. Do you think it would react adversely to Dextrin?

[oskarchem]

It won't change if you put it any thurther in the tube. Personnally with this comp, I don't know how to decrease the flames.

[ghost]

I was really wondering if there was a way to baffle the tube, or maybe cap the top and cut a small hole instead of leaving it open?

[FrankRizzo]

Here's my best smoke comp so far:

 

43% Zinc Oxide

43% Hexachloroethane

14% Aluminum (atomized)

 

I'm housing it in 1" ID, 1/8" walled parallel wound tubes, however, when the mix is ignited, it produces a sizable 1 1/2 - 2" high temp flame out of the top, no matter how far I recess the mix in the tube? Is there a way to arrest these flames? (i.e. just have smoke come out instead of FIRE?)

 

Comp produces EXCELLENT grey/white smoke btw.

 

PS mix is somewhat hard to ignite if you want to try it. Do you think it would react adversely to Dextrin?

Mix in a few percent calcium or barium carbonate. When the carbonates are heated, they absorb some of the thermal energy and also release CO2 gas which will help stop smoke gases from igniting outside the tube opening.

[ghost]

would any carbonate/bicarbonate work? (i.e. baking soda?)

[hst45]

Best guess, yes. That's what I was going to suggest. I use up to 15% sodium bicarbonate mixed with BP meal as delay comp in rockets and in roman candles.

[Mumbles]

Just adding a nozzle might work, say 1/2 ID. so 1/2" hole on the tubes you have. It will help to prevent the comp from getting too much oxygen. The carbonates could help as well. I'd start at 5% and go from there.

[ghost]

I'll give 'em a try and let you know how it goes! Thanks to all!

[ghost]

Okay, NOW I'm stumped... After adding Sodium Bicarbonate the reaction somehow became INCREASINGLY exothermic. Causing the cap with a hole to rupture, then burn. Not to mention the black snake effect that pushed the now on fire cap off of the device... *sob* I just want this to 'efin work!

 

Anything else you guys can think of? or am I just retarded?

[tentacles]

Are you just putting loose comp in the tube, or pressing it in? You could try dampening it with some (DRY) acetone or alcohol. Do not use water with this comp, it will react and run it.

 

I agree, though, that the ZnO/HCE/Al smoke mix is killer.. if only it didn't smell so awful.

[FrankRizzo]

Okay, NOW I'm stumped... After adding Sodium Bicarbonate the reaction somehow became INCREASINGLY exothermic. Causing the cap with a hole to rupture, then burn. Not to mention the black snake effect that pushed the now on fire cap off of the device... *sob* I just want this to 'efin work!

 

Anything else you guys can think of? or am I just retarded?

The reason I suggested calcium or barium carbonates is that they aren't hygroscopic like sodium bicarbonate. Less than 3% should be used.

[ghost]

I'm ramming the mix very thoroughly with a mallet.

 

EDITED: sorry mumbles...

[Mumbles]

There is a big difference between pressing, and what you are doing which is ramming. It may seem like I'm being picky with terminology, but there is a very big difference. If you tried to "press" certain things as you put it, they would explode.

[tentacles]

I'm pressing the mix very thoroughly with a mallet.

Are you filling up the casing, and then ramming it, or are you ramming in increments? You should be putting in less than 1/4" length per increment if you want to get it in there really solid.

 

What do you guys think about a couple % vaseline, ala whistle mix? That could possibly stop the flaming.

 

 

Probably the reason the NaHCO3 made the reaction more aggressive is from water in the mix - as Frank said, it's hydroscopic and will attract water. The water would heat up when ignited and water is very bad for this smoke mix, it will cause a very exothermic reaction all by itself without being heated to steam.

[ghost]

The ramming is being done in increments, about an eighth at a time.

 

So, no more baking soda... got it.

[asilentbob]

What mesh spherical aluminum are you using?

 

Since hexachlorethane doesn't have any oxygen itself... rather its decomposing and the chlorine is burning with the aluminum... ... I think...

 

I really don't know... Personally I think I'd cut back on the aluminum slightly and/or add some calcium carbonate.

[ghost]

Al is 325 mesh (22 micron)

 

Any less Aluminum and the reaction doesn't reach criticality.

[tentacles]

I believe the HCE is the smoke (or a component therof) and the zinc oxide is providing the oxygen to the aluminum in a relatively low powered thermite reaction.

[TheSidewinder]

Hmm.. in one comp that I know of, the Zinc Oxide is actually what makes the smoke. It's Firefox's Composite Smoke kit, which is simply a modified APCP formula (which they also sell).

 

In colored smokes, which require a much lower burn temperature than white or black smokes, the dye must sublime (and NOT decompose or combust) so that it becomes an aerosol. The color dyes discussed elsewhere here require these lower temps, unless I've badly misread.

 

The same is true for the Firefox recipe, but it can burn at a relatively much higher temperature without causing the Zinc Oxide to decompose or combust. Its suspension in the air is what makes such a dense cloud. I wish I still had the little video I made at the WPAG in '06 when I tested some of this. Larry K. saw it, and was amazed at the amount of smoke it made for such a small amount of comp.

 

The stuff is quite amazing to me, too. I cast it into a pop can, but before it was fully cured, I peeled off the can and cut the comp into 1" thick disks, then allowed them to fully cure. It ended up being the consistency of very hard, cured rubber, but pressing a fingernail into it left a permanent dent. Once lit, it combusts with no discernable flame and requires no enclosure. It was, visually, unique.

 

You can hold it at one edge until it combusts VERY near your fingers before it gets too hot to hold (NOT a recommended way to do it, of course, just an observation of how it worked) and looked for all the world like a red hockey puck.

 

If I get the chance, I'm going to make a batch of it for the June WPAG shoot and demonstrate it during the day Saturday.

[GalFisk]

I believe the HCE is the smoke (or a component therof) and the zinc oxide is providing the oxygen to the aluminum in a relatively low powered thermite reaction.

Not exactly, in HCE the Al does reduce the ZnO, which then in turn forms ZnCl2 from the hexachloroethane. The smoke consists mostly of ZnCl, HCl and zinc oxyxhlorides. More detailed info here: http://en.wikipedia.org/wiki/Smoke_screen#Zinc_chloride

[ghost]

So, I actually called the guys at skylighter since they're only a few hours from me, and one of their guys suggested that I use two separate containers, one to house the mix inside of a larger container that is perforated on the sides!?!?! this sounds like it will work, but what materials would possibly stand up to that?

[TheSidewinder]

The inner container with the punched holes won't stand up to it. But it will long enough for the comp to burn out. After that, you can extinguish the cannister. Metabolized beer works well.