Crack color residue

[jas123456789]

First off I know there are already many threads about crack residue but I can?t find specific answer I?m looking for. I want to know why sometimes the residue/ build up in a stem is brownish oily resin like normal but sometimes it?s white coated all the way through and sometime it?s brown right underneath Brillo then rest of way Ismaili whiteish like crystals. Is it just quality of dope? And which is it ?supposed? to be. Thanks

 

[T. Calderone]

I've seen all three and I was told brown indicate better product. I would assume variants would be from the cuts but I'm no expert. I used to wonder what it's supposed to look like as well. It's been years since I've smoked it. Maybe someone else can share their experiences.