Vape cartridges are made through a multi-stage process that starts with extracting oil from cannabis plant material, refining it into a clean liquid, blending it with terpenes for flavor and consistency, and then filling it into small hardware units on precision machines. Each stage involves specific techniques that affect the safety, potency, and taste of the final product.
Extracting the Raw Oil
The process begins with pulling cannabinoids and other active compounds out of cannabis flower using a solvent. Solvent-based extraction is the most common industrial method. A variety of solvents can do the job, including ethanol, butane, propane, and supercritical carbon dioxide (CO2), but ethanol and CO2 are the two workhorses of licensed production.
In CO2 extraction, carbon dioxide is pressurized until it reaches a “supercritical” state where it behaves like a liquid solvent. It flows through the plant material, dissolving cannabinoids and terpenes, then returns to a gas as pressure drops, leaving the extracted oil behind with no solvent residue. Hydrocarbon methods using butane or propane work differently: the gas is cooled or pressurized into liquid form, passed through the plant material to strip out the desired compounds, and then purged. CO2 is considered a cleaner option because it leaves fewer residual chemicals, but hydrocarbon extraction can preserve a broader terpene profile.
Newer techniques like ultrasonic-assisted and microwave-assisted extraction use energy waves to speed up the process and reduce the amount of solvent needed. Conventional methods like Soxhlet extraction require longer run times and larger solvent volumes, making them less efficient for high-volume production.
Refining the Extract
Crude cannabis extract straight from the extraction machine isn’t ready for a cartridge. It contains waxes, lipids, fatty acids, and plant matter that would make the oil cloudy, thick, and harsh to inhale. Refinement strips all of that out.
The key step is called winterization. The crude extract is dissolved in ethanol or isopropyl alcohol, then placed in a freezer at temperatures between 0°C and negative 20°C. It stays there for anywhere from one hour to 72 hours, depending on the manufacturer’s protocol. During that time, the waxes and fats solidify and separate from the liquid. The mixture is then cold-filtered, first through a lab filter to remove the visible solids, then through fine syringe filters (as small as 0.2 microns) that catch remaining plant particles and even bacteria. What comes out is a clear, stable liquid with no visible impurities.
Many producers take refinement a step further by distilling the winterized oil. Distillation uses heat and vacuum pressure to separate individual cannabinoids by their boiling points, producing a highly concentrated oil often called distillate. Distillate typically tests above 80% THC or CBD and is nearly flavorless on its own, which is why terpenes get added back in later.
Adding Terpenes for Flavor and Flow
Distillate is thick, almost like honey. It also lacks the aromatic compounds that give different cannabis strains their distinctive taste and smell. Terpenes solve both problems at once: they thin the oil to a viscosity that wicks properly inside a cartridge, and they restore flavor.
Terpenes are added at concentrations between 5% and 12% of the total volume, depending on the hardware. Ceramic coil cartridges handle higher concentrations (8 to 12%) effectively, while older cotton wick designs perform best at 5 to 8%. The source matters too. Cannabis-derived terpenes are extracted from actual cannabis plants and reintroduced to match a specific strain profile. Botanical terpenes come from other plants like lavender or citrus and are blended to mimic cannabis flavors, though they typically require slightly higher percentages to achieve a comparable taste.
Mixing happens at around 60 to 65°C. That temperature is warm enough to reduce the distillate’s viscosity so the terpenes incorporate evenly, but cool enough to avoid evaporating the volatile aromatic compounds. Too many terpenes create a harsh, irritating product that can actually leak from the hardware. Too few leave the oil too thick to vaporize properly.
Cutting Agents and Additives
Some manufacturers use additional thinning agents beyond terpenes. Propylene glycol (PG) and vegetable glycerin (VG) are common in nicotine e-liquids and have historically appeared in cannabis cartridges as well. Medium-chain triglycerides (MCTs), derived from coconut oil, have also been used as thickening or diluting agents, particularly in lower-cost products.
The most notorious additive is vitamin E acetate. It was widely used as a thickener in illicit cartridges because it mimicked the appearance of high-quality oil. During the 2019 EVALI outbreak, some tested cartridges contained more than 30% vitamin E acetate. The CDC and FDA concluded it was strongly associated with the lung injuries, and it is now banned from cannabis products in many states. Reputable licensed producers have moved away from all unnecessary cutting agents, relying solely on terpenes to achieve the right consistency.
The Cartridge Hardware
The physical cartridge is a small assembly of just a few components: a tank that holds the oil, a heating element, a center post that connects to a battery, a mouthpiece, and seals that prevent leaking. Tank materials vary. Glass is the most common in premium carts because it doesn’t interact with the oil. Ceramic, metal alloy, and plastic are also used, and each affects taste, durability, and leak resistance differently.
The heating element is either a ceramic coil or a cotton-wrapped wire coil. Ceramic coils heat more evenly and tend to produce cleaner vapor, which is why they’ve become the industry standard for cannabis oil. The mouthpiece is usually plastic or metal and is designed to screw or press onto the tank after filling.
Filling and Sealing
Cartridges are filled on automated machines designed for high precision. The blended oil sits in a heated reservoir that keeps it at a consistent temperature so it flows smoothly through the tubing and nozzles without clogging. A positive displacement pump, usually a rotary piston or gear pump, measures out the exact volume for each cartridge. These pumps deliver accuracy within plus or minus 0.01 grams, meaning every cart in a batch gets virtually the same amount of oil.
Needle valves or solenoid valves at the nozzle tip control when oil starts and stops flowing, preventing drips between fills. Servo motors move cartridges along a turntable or conveyor, positioning each one under the nozzle in sequence. After filling, a capping head picks up the mouthpiece and screws or presses it onto the cartridge with consistent torque to ensure a proper seal without cross-threading. Some production lines include a separate spin-tightening station for a final torque check.
High-end filling lines also integrate a precision scale that weighs each cartridge immediately after filling. If one comes out under or over the target weight, the system adjusts the pump output in real time for the next unit. This feedback loop is the gold standard for fill accuracy across large batches.
Lab Testing and Quality Control
In regulated markets, every batch of filled cartridges must pass third-party lab testing before it can be sold. Labs issue a Certificate of Analysis (COA) that reports pass or fail results across multiple categories: cannabinoid and terpene potency, residual solvents and processing chemicals, pesticides, heavy metals, microbial impurities, mycotoxins, moisture content, and foreign material.
Heavy metal testing is particularly important for vape products because the heating element and other metal components can leach trace metals into the oil. Industry limits follow pharmaceutical standards: 0.5 micrograms per gram for lead, 0.2 for arsenic, 0.3 for cadmium, and 0.1 for mercury. These thresholds are based on U.S. and European pharmacopeia guidelines. A batch that exceeds any limit fails and cannot be sold.
Potency testing confirms the labeled THC or CBD percentage matches what’s actually in the cartridge. Residual solvent testing ensures that extraction chemicals like butane or ethanol have been fully purged. In California, state-licensed labs are required to follow standardized testing methods set by the Department of Cannabis Control, which helps ensure consistency across different testing facilities.