Then, observe the ash. If the ash color is that of a darker gray or black, that could mean that there were unwanted compounds or even minerals in the cannabis you consumed. But if the ash color is white or light gray, then the consensus is that cannabis is very clean. If the ash turned black or dark grey, this could mean that that cannabis wasn’t cured or flushed properly. When the growing process leaves minerals and unwanted sugars because of improper curing, the smoker can observe a feeling of throat burning as well as dark ash.