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White Ash: Flushing Out Old Stereotypes

What does the color of ash tell us about cured Cannabis?

It’s not uncommon to run into smokers that associate white ash with cleanliness and quality. But when it comes to the burning of buds, where did this old toker’s tale come from? And what does the color of ash tell us about cured Cannabis and flushing?

When asked about the color of ash, most folks offering up the aforementioned adage will tell you that bud burning white signifies a proper flush of the plant – a process where water is used to remove nutrients and trace elements. There are conflicting opinions among growers and gurus alike about methods, benefits, and even the efficacy of flushing as a practice. 

Dr. Allison Justice and Dr. Markus Roggen bring backgrounds in horticulture, organic chemistry, and more to multiple branches of the industry. In an article for Cannabis Business Times, the duo explored the science behind ash, starting with what contributes to its color:

Research into ash from wildfires points to burn temperature as the main factor in determining ash’s properties. With increasing combustion temperature, the charred organic material and organic nitrogen concentrations decrease, and the ash color lightens from black to gray to white.

In theory, less hot organic material entering the lungs should make for a smoother hit. In this light at least, the white ash ideology may just hold up. Many other factors influence combustion temperature, however, and a crop grown for human consumption presents a set of different variables than the ash from wildfires.

The practice of flushing is highly personalized among grows and while it shouldn’t be viewed as inherently bad, maybe it’s time to reevaluate our standards from a consumer standpoint.

In the Cannabis community, the curing process of flower is commonly associated with the resulting ash color. This process directly correlates to moisture content and most certainly affects combustion temperature. Data on Cannabis combustion and moisture content is limited, but the studies on wildfires and vegetative burning points still provide insight. Most results lean toward a plateau effect when it comes to moisture. Too little, and most plant matter will burn at a rate too fast to reach the high temperatures needed to create white ash. Too much moisture, and similar outcomes are exhibited.

Determining the quality of bud (and tracking combustion rates) is, of course, more complicated than simply observing moisture content and ash color. With each plant providing a unique set of characteristics, everything from bud structure to terpene profile can influence your smoking experience. 

In recent research, the RX Green Technologies R&D department – headed by “expert plant scientist” Dr. Stephanie Wedryk – analyzed “the effects of different flushing times on chemical profile, flavor, and smoking characteristics in Cannabis flower.” Flushing periods were applied to groups of Cherry Diesel (Cherry OG x Turbo Diesel) in zero, seven, ten and 14-day increments. The cured flower was evaluated by “a group of industry experts” in a blind taste test that rated the consumption characteristics and flavor:

Overall, the duration of the flushing period had no impact on flavor, smoothness of smoke, or color of ash… The seven-day flush period had the highest “bad” rating (21.1%) and the 0-day flush had the highest “great” rating (16.7%).

The quality of hit was not rated significantly different among samples, but researchers did note that contrary to previous beliefs, “smoothness of the smoke increased with decreasing flushing time.”

When it comes to methods, it’s important to note that RX Green used its own products for the study and that the company makes a portion of its profits off of nutrients, supplements and additives. It’s safe to assume some bias in the analysis, but with few academically-funded (Cannabis) terpene studies, there’s still valuable information to be considered.

Take, for example, their statistical findings on yield, THC and terpenes. While data didn’t point to any significant losses in the “flushed” test groups, terpenes exhibited the only consistent decrease over longer flush periods (losing 0.18% between zero and 14-day flushes). Factors like grow conditions, care, and plant variety also play a part in the cycle of terpene preservation and loss, but additional studies present the possibility of deteriorating a plant’s profile when flushing.

A 2017 piece in the Journal of Molecular Liquids on “Terpenes solubility in water and their environmental distribution,” looked at the solubility of seven monoterpene structures. Researchers found that (with one exception) “the solubility of terpenes in water shows a (monotonical) increase with temperature.” While most terpenes may remain in the plant during a flushing process, there is data to support some loss. Specifically, when using water upwards of 75 degrees Fahrenheit – a method that, according to horticulture author and educator Ed Rosenthal, is commonly practiced to increase nutrient movement out of the plant.

The practice of flushing is highly personalized among grows and while it shouldn’t be viewed as inherently bad, maybe it’s time to reevaluate our standards from a consumer standpoint. With all of the products, growing methods and plant varieties out there, it’s difficult to generalize what makes ‘good’ or ‘clean’ flower. Most seasoned smokers would probably agree that buds should be healthy, potent, high in terpene content, and free from any harmful additives. It’s 2020 and the white ash method probably isn’t the best indicator for any of these characteristics. Most Oregonians now have access to enough consumer information to make informed decisions about the quality of flower before lighting up and inhaling. 

Maybe it’s time we finally put this old stoner stereotype to rest.