12 replies to this topic

[robfir]

I measured out 10g caster sugar into a shallow tin pot, and melted it down into a light brown liquid as gently as I could on a gas camping stove (outside).

I then removed the tin from the heat, put 10g KNO3 into the mix, stirred it, then returned it to the heat, stirring contstanly until there was a consistent shade of brown in the tin, with no white bits.

I then removed it from the heat, and allowed it to cool and solidify. I now had a layer of hard brown caramel in the bottom of my tin, I tried to scrape it out, but soon realised what is meant when people say it "sets like concrete", so I lit it in the tin, it burned well, only stuttering at the start, my only dissapointment with it was the rather modest amount of smoke given off. If possible, i would also like it to give off less of a flame, or less heat.

I'd appreciate any improvements to my recipe and method.

[paul]

... put 10g KNO3 into the mix, stirred it, then returned it to the heat...

*bing*! Thats not the best idea.... If you use normal sugar DON?t put it back to the heat source!
Its too dangerous


Don?t use gas stoves! They cause hotspots on the pans ground and can lead to an accidental ignition.

And for smoke, i would suggest you to use sorbitol Much lower melting point and so less dangerously

greets,
paul

[Yugen-biki]

Congratulations.

I have seen many recepies where distilled vineager is added. Why and how much am I not sure about. I have never really take interest in smoke. Try to increase the ammount of sugar untill it barely burns. This will get you a composition that burns as incomplte as possible --> generates as much smoke as possible. The smoke is basicly unburned sugar. Try something like 30% KNO3.

BUT a few words of advice!
Heating this mixture may cause severe burns. Especially when you get your confindence up and start to make larger batches. Just because nothing happened before doesn't make it safe. An alternative to melt it is to grind it very fineley.

Good luck!

[robfir]

My 10g of sugar had too little mass to stay molten long enough to stir in the KNO3, and I also found it hard to stir in, the volume being so small. I did find the evident risks involved, and my lack of knowledge of the results of ignition, pretty stressful, so I'm all for another way to get them melted together. What can be reccomended? Do I just have to make larger, easier to handle, batches?

[paul]

Its as safe as possible if you melt the slightly more expensive sorbitol till it gets clear.
Take it off the heat and stir the KNO3 in it. So, there is practically no risk of ignition if you don?t work nearby the heat source...

@ Yugen-Biki: Thats not really true Most smoke is given off when the amount of sugar is near 35%...
For sorbitol, 2/1 KNO3/sugar works best.

And i think the smoke consists of water and stuff like potassium carbonate etc...

greets,

paul

[Phoenix]

Flame based heating is not really recommended for doing this, but I know that people do use it without incident. A somewhat improved way to heat the mixtrure might well be to have a tray of dry sand over the burner, and the vessel containing the smoke mix standing in the sand. This would help to spread the heat from the burner and reduce the tendancy for hot spots. One need hardly mention that eye (or better, face) protection is an absolute must, as is protection for the hands, which are likely to be directly over the pot of composition. Do not underestimat the importance of eye protection here - there is a chance that the composition could ignite, and if it does, good goggles will probably save your sight.

Having a read through the Propellant's section of Richard Nakka's site (Scroll down) might be a good idea, as KNO3/Sucrose rocket propellant is made in much the same way as smoke mixes, and many of the same rules will apply.

[robfir]

Thanks for all your help guys, I'll look around for some sorbitol, make my second batch with the help of your advice, and tell you how it goes.

[Yugen-biki]

@ Yugen-Biki: Thats not really true  Most smoke is given off when the amount of sugar is near 35%...
For sorbitol, 2/1 KNO3/sugar works best.

You may be right. When I tried it I got the most smoke out of it with somithing like 60:40 sugar:KNO3.

And i think the smoke consists of water and stuff like potassium carbonate etc...

I say this again, I'm not really in to smoke and I don't really know much about it. But here is what I think.
KCO3 and H2O[aq] are most likely a part of the somke. But I'm not sure this is the case with sugar and KNO3. Say that we have a mix that burns "clean" with only water and carbondioxide coming from the sugar. This would generate KCO3 and H2O[aq] smoke particles.
What if we lowered the ammount of KNO3. This would generate small carbohydrates, and similar, from unburned sugar. This smoke is much darker allmost black. And the smoke from 80:30 KNO3:sugar is light gray/white. And in my experience the alternative with darker smoke generates a bit more of it.
Or it might be an optical effect.

[robfir]

This smoke is much darker allmost black.

This is what I hope to acheive - dense black smoke in reasonable quantity.

[adamw]

Add bits of rubber into it? Or use a dense oil product like tar / pitch or even anthracene. Then there is the expensive option - Naphthalene.

[curious aardvark]

I like smoke :-)
The logical way of thinking that you add more sugar and get more smoke doesn't work as the excess sugar seems to catch fire which redeces smoke.
I haven't tried this myself yet (yet to make bp this time round) But everyone must have noticed the huge amounts of smoke given off when bp burns. So mixing some bp in with you kno3 and sugar mix ought to give a good smoke boost. I also add a little plain flour to slow the reaction down.

By the way use icing sugar instead of castor works better. Grind the sugar and nitrate together in mortar and pestle (no need to overdo it) and damp to stiff icing consistency, knead inside plastic bag or plastic container for few minutes and leave to dry. Just as effective as the melting method but with the serious added advantage that you can shape the mixture and it will dry hard as rock. Also can be used as a base for stars or comets. Just embed smaller stars in a lump of this stuff and launch :-)
I tend to put blobs in the centre of squares of fuse paper and twist the corners together. You then get a small smoke device with built in fuse. Depending on the speed of your fuse paper you can get anywhere from 2-3 minutes down to 20 seconds fuse time :-)
Practical uses: I can use weighted missiles with my sling and measure distance as the smokebomb will burn for several minutes and is very easy to find :-)

But for effective smoke b**bs (paintballing etc) you can stuff larger amounts of this stuff into NON-Flammable metal or plastic tubes (we don't want to set fire to the woods now do we :-) stuff a dozen non-safety matches in the top so they are strikeable yet still touching the mixture and you've got a simple ignition (scratch on anything rough) cheap and effective throwable smokebomb.
Make sure you you don't seal the arse end of the tube before it's all dried :-)
Also make sure you've got lots of holes otherwise it won't all dry. Actually with this stuff it will burn really well when still wet, give you more smoke and burn longer. So in that respect it's ideal for a quickie smoke b**b. Also if you use a small amount with a 22 blank in the middle you've got a fairly effective - but probably illegal, so this is purely hypothetical :-) - banger.
22 blanks are also useful to stick in the middle of a star mix for a really easy to make and cheap mini retort :-)

I have tried mixing a very small amount engine oil into a batch of the icing mix and it seemed to work quite well. That was a few years ago though and my memory could be deceiving me :-) I'm sure I got some really thick black smoke from it. In fact if you use a small amount of engine oil (poundland sell litre bottles of the stuff) to make your icing paste (no water) it should be excellent.

Edited by curious aardvark, 01 September 2005 - 03:57 PM.

[adamw]

Don't make things out of ordnance such as .22 blanks! It's just asking for trouble. And bringing a home made device to a paintball site is a no-no.

[curious aardvark]

he's just a spoil sport isn't he. But it does all depend on the paintball site, and smoke devices are cool :-)
Hey the 22 blank devices were 18 years ago :-) You telling me you never made anything a bit 'dodgy' when you were a kid ? Or salvaged anything from commercial fireworks ? It's the same thing. And I did say it was probably not a good idea :-)