The crackling just means that the weed isn't dry totally...it is the moisture in the marijuana... I have flushed and not flushed my pot, and never had crackling either way...I am not sure where this idea came from, but I think it is another one of those things that just gets started on a forum and spreads...just like the whole the ashes won't burn white... What a joke... Anything turns white if you burn it long enough...Anytime you see white ashes in your bowl you have just roasted it too much you cheap bastard...it was cashed 3 puffs ago...lol
Here is an experiment... Take a lighter and a large piece of paper and go outside... Now set a small corner of the paper on fire and really quickly blow it out... The paper is now burnt black...now take that same piece of paper and put it down on the ground and set it on fire and then wait...you will notice that at first burn the paper turns black, then as it burns more it turns white... That is the way any carbon based life form burns... It won't' stay black whether it is flushed or not, or covered in ink, or a live branch or whatever...it all burns to white dust given a hot enough flame for a long enough time.... You should never roast your weed til it is white...just no need... Every bowl I cash out is just black hard stuff, cuz it doesn't taste good and makes me cough if I burn it til it turns white, but it can, and will...for real...
So let's try to stop this weirdo easily disproven myth...
Here is a better experiment... Take a glass of water and a couple of drops of plant food and just stick a small plant trimming in there...in a few days take it out and let it dry out... When it is totally dry take it outside and set it on fire...bet once it is totally done burning it is just a white pile of ash...