FYI candles don't soot very well unless you blow them out. The bright yellow region of a candle flame is high in soot (it's the hot soot that's glowing yellow) but a well-designed flame finishes the burn out of the soot into CO or CO2.
If you have a candle made from a wax that is too low-temp or if there's an A/C unit or fan on the flame will not close at the top and may move around. These flames will continuously create soot but not a lot.
You can create as much soot as a blown-out candle but in a continuous fashion by "quenching" the flame. Take a metal knife and cut about halfway across the candle flame's yellowest part - tilt the blade up a bit so the sooty air flows off. You'll get a huge amount of soot - for a short period of time. The problem is that the knife blade gets hot and no longer stops the combustion process - the flame just bends around the knife so you've got to keep your flow blockage cooled. However, if you can manage it you'll get a much blacker and continuous supply of soot to play with.
Of course, if you're the camping type that has a kerosene lamp you can always just adjust it so too much of the lamp is exposed. That's another way to create a huge sooty mess - but one that can make interesting patterns.
Experiment with cookies through the soot - especially one that lets a single line of light through. The cross section of the soot field can be far more interesting than a flash exposure of the cloud as a whole.
p.s. probably way more info than you wanted but in graduate school I studied combustion...I just can't help myself.