Colored smoke darkening over time

[Guest]

I'm kinda new to making my own pyro and I started making some colored smoke using the firework cookbook kit and formula (5/3/2/1 dye chlorate lactose magnesium carbonate).

 

In small devices around 11 grams the smoke is a rich blue color but when I went up to 44 grams the smoke turns from blue to a blue-grey color near the end of the burn.

 

Reading on this it seems like the dye is getting too hot and starting to burn. Is there any trick in assembly of the device to help prevent the darkening of the color? Right now im just been wrapping tp rolls in hvac foil tape and poking a hole in the top to put in a fuse then filling it with the lose powder. Crude I know. When I pressed the composition with my body weight the amount of smoke produced was reduced greatly so I'm having a problem finding a good balance of output and color.

 

Any ideas?

[dave321]

you could try adding a coolant such as sodium bicarbonate or magnesium carbonate, the latter will have less effect on the burn rate.

alternatively try adding some other material that also sublimes like colophony or even ammonium chloride.

this may dilute the colour slightly but help preserve the dye

[Guest]

I do have magnesium carbonate in the mix but its a pretty small amount 1 gram per 11 grams total mix...can it hurt to add more parts of magnesium carbonate to the mix?

[Arthur]

The important detail is that the smoke producing burn MUST be fuelled only by the incorporated oxidiser NOT by atmospheric oxygen. The answer usually lies in the structure of the casing cardboard. Not knowing your casing shape, just consider the smoke generator as a rocket with a large diameter long nozzle. The nozzle on a smoke is critical to function. With black smokes using naphthalene a metal outer can helps retain the naturally volatile naphthalene solid.

[Guest]

That would make sense...ill try a few more ways of making them trying to focus on a good seal and see how that works out thank you.

[Arthur]

The flame end point must be inside the casing, the smoke and the sublimed dye must pass, cooling, away from the generator. Darkening during the burn is caused by it having too much flame or oxidiser and the dye molecules getting charred, likewise, fading to grey is usually the big organic dye molecules getting broken and loosing colour.

[Mumbles]

In my albeit limited experience, the smoke usually turns black to dark grey when it's being pyrolyzed inside the casing. This is generally a sign of the casing or composition getting too hot. The smoke will often turn white to light grey if it's being burned outside the casing. A visible flame can make this pretty obvious too. To me it sounds like you're experiencing the first one. This does happen with bigger devices that burn longer. If you cut a spent tube open you might observe increased charring or consumption of the walls as well.

 

Bumping up the carbonate a bit might help. Another thought might be to try to soak the tubes in some sort of material to provide heat resistance, like a thinned out sodium silicate solution. Increasing the size of the choke/nozzle may provide some help too.

[Arthur]

Most compounds do NOT simply scale up or down. Small rockets use a BP like comp, as they get bigger they need a slower more charcoaly comp, small stars need fine powders (50 - 100 mesh) big stars will work with coarser ingredients. Your smoke may need some adjustment to the comp as it gets bigger.

[mx5kevin]

I had a similar problem magnesium carbonate fixed the issue. Tested with Purple Rodamin B, Solvent Red 111 C15H11NO2, Solvent blue 78, C16H142O2, Solvent Orange 60 C18H10N2O, works at all of them.

 

The working composition:

 

36% Smoke Dye, 27% Potassium Chlorate, 18% lactose, 19% Magnesium Carbonate,

 

MgCO3 decompose on 350 °C. Carbonates what decomposes at high temperatures like Na, K does not working the setup.

 

See: SMOKE BOMB COMPOSITION

 

The color was washed out, and smelled like burnt rubber the smoke without MgCO3. I tried before Dye/KClO3/Lactose 5/3/2 but it didn't work.

Edited April 1, 2022 by mx5kevin