Well it's a matter of fuel and air mixture ratio like in any combustion. Too little fuel (tobacco light pack) and too much air (loose draw) means quick burn and little smoke, causing tunneling most times. Or heavy pack plus tight draw, equals not enough oxygen for proper smoldering leading the amber to turn off.

The weird thing I dont understand, is why I sometimes (like 3% of the times) I get a stick that turns into charcoal instead of ash. I think it has something to do with the cherry getting too hot, but not too deep which may cause the eat to bake the tobacco instead of burning it. I have no clue, but I know when I start seeing brittle ash I'm tossing it.

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