ive read that the color of the ash on your j or blunt is a good indicator of the purity of the weed. they said white ash is clean weed, but the darker it is, the more chems left in it from growing.. ie not flushing. i dont know how true that is but it makes sense to me and from my experience, the darker the ask, the harsher and harder the smoke. white ash give a nice clean high and tastes good. not ALL the time is it this way but enough to convince me, take a look at a cig ash and your joints ash
the cig is always so white on marlboros