Black burning ash marijuana


This debate in the cannabis community has been raging for what feels like a ZILLION years. But does the colour of your burned ash actually dictate quality?

A guy drawing on a whiteboard diagram

Here’s what some people assert: If it’s black burning ash instead of white or grey, then you are dealing with a plant that was over-fertilized or treated with chemicals. Since the taste, flavour, strength, and look of bud are not affected by the added use of said chemicals, the only way to tell is to smoke it… So here we go.

The Argument

Properly flushed cannabis will have consistent white ash during the burn. The whiter the ash, the cleaner it’s burning, the smoother the inhale and exhale. In addition, improper flushing may cause throat burning and coughing. If it’s been flushed well then there should be no growth products in your bud. But purging the plant in the growing process takes extra weeks and to cut costs for a larger return, they put out unflushed garbage as opposed to properly flushed products.

So does this argument carry and validity?


We need to look at two different stages in the farm to table process: flushing and curing. Clean water is supposed to remove any residual trace of carbon or nitrate potentially present in the farming process. If it’s not dried properly, then you might argue the chemicals didn’t perspire entirely. But the way in which you smoke it can affect the colour too, without any extra fertilizers or bad chemicals present. So you might get a false positive from lighter fumes, rolling paper dyes, or some other factors unknown. This is probably something most people who smoke weed don’t even consider. But heavy tokers looking for that high THC perp skerp, know this is a real thing.

a weed joint smudging black on white paper

Organic or Neutral Smoking Accessories

The type of paper, the humidity of the weed, how fine you grind your weed, and how strong your pull is, are factors worth considering because each will change the colour of the ash. For instance, when using blunt paper, you’re more likely to have very white ash, because the material burns at a higher temperature for longer periods than regular rolling papers.

two different version of joints

If you are using neutral smoking accessories/rollies (no chemical additives, etc) then there is a test you can do to see if the weed has been washed properly or not. Here’s what you do: Smoke down a joint and ash it over the white paper on rolling matt or tray. Then with your finger, rub the ash. If the ash turns to powder and is a greyish or white colour, then it’s been properly washed or not had bad chemicals used in its growing process. If the ash is a bit sticky and turns a colour that is closer to black than white, then there is a decent chance that the weed was not washed properly. But does this mean that your weed is shit?

Absolutely not.

Carbon & Mineral Content

So here’s the thing… Any carbon-based combustible matter will first turn to charcoal and appear black. It’s the persistence of heat that chemically alters the substance. So if you keep on burning the plant to the point where there is no carbon left, you’ll reduce the plant substance to its mineral content – which is most likely calcium, phosphorus, potassium, sodium, and magnesium. When you see this, you’re now smoking weed that appears to leave behind white ash.

Point is that white ash has been smoked completely, whereas black ash still contains resin. And you can still smoke weed once it’s burned black because there’s still juice in there to get you high. Some strains will turn white more quickly, but that is not necessarily a tribute to quality. When you burn things, they are going to turn black first, and then ashy. The harder you pull will also dictate how long this change takes.

burnt wood ash in fire place

Take a wood-burning fireplace for example. The wood catches fire and turns black, but eventually, after completely burning threw (the carbon-based substance) we see white ash. This is completely normal, and aside from the fact that weed contains cannabinoids that get you high, there’s not much difference in the mineral content that’s leftover (if any at all).

The Best Marijuana Grading System

On the flip side, white ash can be a bad sign because very dry weed will tend to burn at higher temps, making it burn more throughout. Once you smoke enough joints it becomes intuitive whether you’re smoking good or bad weed, and if you want to take your knowledge to the next level, read our Marijuana Grading System.