Black Gunk Residue From Meth

I've pretty much got the synthesis process down except for the cleaning part.
I'm using RP (red phosporous)and IC (iodine crystals).
My dope is fairly good.
But, when I smoke it, it ruins pipes because of a black tar like gunk.
I've been trying to figure out the best cleaning method.
I usually don't make more than 10 grams at a time, so I don't want to lose too much.
I have the concept of recrystallization down, but,I'm trying to figure out the perfect solution. In recrystallization tutorials they say the perfect solution requires the dope to do be insoluble in it at room temperature and to dissolve any where up to 70 C. From what I've learned online, people like to use pure alchohol solvent, bring to a boil and saturation point, then add acetone, cover and slowly cool.
My questions include;
Does dope stay insoluble in alchohol at room temperature?
If so why add acetone?
Does anyone know what this black Gunk is specifically? (My guess is perhaps some Coleman fuel(from last step w/ caps full of dh20 and drop of hcl acid), sodium hydroxide sludge(from step before that), or a combination of two)
OR if anyone has a better idea?

Thanx 4 all ur help

 

Idk what it is called but it comes from when you burn it in the pipe don't hold the lighter there to close oven cleaner works great for cleaning it or rubbing alcohol

 

Sounds racist.