It is more than likely you've experienced it before. After purchasing a new vape cartridge with an attractive, golden, translucent oil, you enjoy its clean, potent, and delicious taste. However, after a couple of weeks or months of sitting in your drawer, or having been partially consumed, you notice something has changed. The oil has turned a murky amber, a dark brown, or even nearly black. Your first thought is probably, "Is this still safe to vape?"
I've had that same thought many times throughout my years of using and studying cannabis products, and through those experiences, I've come to understand that the color change of oil is a relatively common occurrence, resulting from multiple factors. While it is not always indicative of a problem, in many cases, it is simply a natural progression of the oil's lifecycle. Let me help clarify the process for you.
The Chemistry of the Change: It’s More Than Just One Thing
There are multiple reasons why your vape oil will darken. It's not a single issue, but rather a combination of both chemical and physical reactions. Based upon my experience, a cart that darkens slowly over time with use is generally going through normal oxidation, whereas a cart that turns black quickly after a single use is likely the result of overheating.
1. Oxidation: The Most Common Reason
This is undoubtedly the most common reason that causes the oil to darken, and it is a process I have seen occur with everything from my homemade carts to the premium carts available in stores.
What Is Oxidation?
Oxidation is a chemical reaction that takes place between the compounds present in your oil (the cannabinoids such as THC and CBD, and the terpenes) and oxygen. These two reactants cause the molecules to alter their structure and create new ones. Think about what happens when you cut an apple; the inside of the apple will start to turn brown immediately. The same type of reaction occurs with vape oil. The once-clear golden liquid gradually begins to darken and turn amber.
In my past, I stored a half-used cart in a warm car for a month. Upon opening the cart, the oil was much darker, and had a stronger, "skunkier" taste. The potency appeared to have decreased, which confirmed that the delicate terpenes and some of the cannabinoids had broken down due to oxidation. There is a simple solution: limit air exposure to your cart. Always store your carts with the open end facing up to minimize the amount of the oil coming into contact with the air bubbles, and always put the cap back on when you're finished vaping. Storing your carts in a cool, dark place is essential when you plan to store them for a longer period of time.
Heat Degradation: The Fastest Way to Ruin Your Oil
While oxidation is a slow-burning fire, heat degradation is a quick punch. Of all the reasons that cause the most extreme color change, heat degradation is the fastest way to ruin your oil.
How Does Heat Damage Your Oil?
Heat accelerates all chemical reactions, including oxidation. Additionally, excessive heat can also break down the cannabinoids and terpenes in your oil. Using a battery with too high a voltage is the number one contributor to this problem. I have personally tested this scenario: using a high voltage battery (more than 3.8v) on a thick live resin cart resulted in the oil next to the atomizer coil turning dark brown after only a few extended pulls. The harsh, burned taste was immediate. Studies support this finding; cannabinoids begin to degrade and convert into other compounds like CBN at temperatures above 200°C (392°F), which can lead to a darker color and a more sedated, less energized high.
Protecting Your Oil
Use a low-voltage battery. I do not go above 2.8v-3.3v for most distillate and live resin carts. This will give you a smoother tasting experience, protect the integrity of the oil, and prolong the lifespan of the cart itself. Also, do not leave your vape pen in direct sunlight or in a hot car because the ambient heat will slowly cook the oil from the outside in.
3. Clogging and Re-Burning: The Vicious Cycle
Clogging and re-burning is a very real issue that I have seen far too many times, especially with older or lower-end hardware.
Clogging Issues
When a cart clogs, often with a thick, dark oil that has hardened in the mouthpiece or the intake holes, you need to either preheat the battery, or take a hard, forceful pull to unplug the clog. Either way, the act of preheating the battery or taking a hard pull will apply intense, direct heat to the compromised oil, thus burning it. Then the burnt material will mix with the remaining fresh oil in the reservoir, and contaminate the rest of the cart, causing it to turn dark. It's a vicious cycle; the clog causes the burning, and the burning causes the clogs to happen again.
A Solution to Clogging
If you find yourself experiencing clogs with your cart, try clearing it gently. Take a firm, but short pull without firing the battery and see if that clears the clog. If you have to apply heat, use the lowest preheat setting possible and only for a second. The best solution to prevent clogs from happening in the first place is to store your carts upright and not overtighten them on the battery, which can damage the internal seals.
4. The Initial Quality of the Raw Materials
Not all dark oils are the result of post production problems. Some oils will initially have a darker color prior to entering the cart.
The Extraction and Filtration Method
The initial color of cannabis oil is largely determined by the extraction method and how well the extracted oil was filtered. CO2 oil, for example, will typically have a darker, greener color compared to a highly refined and filtered distillate, which will typically be water-clear or light gold. I have received carts from reputable extractors that had a deep amber color right out of the package and tasted excellent and clean. This is often the result of the processor extracting high concentrations of naturally occurring cannabinoids and using a minimal filtration process to preserve more of the plant's original profile, including lipids and waxes that can add to the darker color of the oil.
My Viewpoint on Purity vs. Color
A dark color right out of the package does not automatically mean it is unsafe to vape. It is more important to evaluate the brand's reputation. A dark cart from a trustworthy, transparent brand that supplies lab reports is safer than a suspiciously clear cart from an unknown brand. The key is consistency; if a reputable brand produces a batch of carts that are significantly darker and taste bad, it could indicate a problem with their starting materials or extraction methods.
5. The Natural Separation of Compounds
This is a lesser-known reason for oil darkening, but it is definitely noticeable to someone who pays attention to details.
Separation of Compounds
As you continue to use your vape oil, the various compounds present in the oil can begin to separate themselves, depending on their density and viscosity. You may see a darker band of oil at the top or bottom of the cart. These bands are likely a concentration of different cannabinoids and/or other plant compounds that have separated themselves from the main solution. When you vape, you are essentially consuming this mixture unevenly. As you reach the end of the cart, you may be vaping a greater concentration of the darker, denser compounds, creating the illusion that the entire cart has darkened.
A Quick Fix
If you observe separation in your oil, gently heating the cart (rolling it in your hand, or briefly placing it in a warm—not hot—location) can re-distribute the compounds and blend the oil, allowing you to vape the cart from beginning to end with a consistent product.
The Final Puff: Knowledge is Power
When you see your vape oil become darker than before, it may cause concern; however, this usually does not signal an emergency situation. Most of the time, the color change is simply a result of the oil becoming oxidized along with the normal usage of the cart. If your vape oil becomes consistently darker (due to oxidation) while tasting like chemicals/burnt and losing potency quickly and/or getting clogged regularly, it indicates your vape carts have become less potent due to user negligence or a bad product. Understanding the above 5 main reasons for the decrease in the quality of vape oil (oxidation, heat degradation, clogging, low-quality of the initial products used to create the vape carts and natural separation), will allow you to take the proper measures to protect your vape carts from degrading prematurely, and enjoy each use as much as your first.