Your New Cannabis Vape Cartridge May Not Appear Full – But It Is

As a regular cannabis vape cartridge user, you may have noticed that even when new, your vape cartridge doesn’t look full. You have probably wondered if you are getting a full cartridge of oil. In this article I will list the different wicking materials and coils and clarify why this phenomenon occurs by defining capillary action. I will also explain the different forces at work that affect the levels in a vape cartridge, define capping and sealing, discuss storage angles and how different oil viscosities affect capillary action. 

For those who have never used a vape pen, a pre-filled cartridge with cannabis oil is heated by a battery, producing vapor which is inhaled. By the time you use your device, some of the cannabis oil has been absorbed by the wicking material inside the coil. This is the result of capillary action which is defined below.

What is Capillary Action?

Capillary action is defined as the spontaneous flow of a liquid into a narrow tube or porous material which occurs without the force of gravity. The main factors in capillary action are cohesion and adhesion.

Example: Color a glass of water with food coloring and then place a stalk of celery in the water. You can observe capillary action as the food coloring moves up the celery stalk.

Different Vape Cart Wicking Materials

  • Porous ceramic
  • Quartz
  • Cotton where a coil of wire is wrapped around a small cotton wick.
    This material does absorb a lot of oil, but it is easy to burn the wick which produces a burnt flavor and often requires coil replacement. More likely to happen with high viscous oils or higher voltages

Different Coils

  • Ceramic coils in which a wire is wrapped around a small cylinder. Gaining in popularity. Good heat retention. Safer with higher voltages
  • Quartz coils
    Heat up quickly. Less heat retention

Environmental Forces on Capillary Action

Temperature, pressure and humidity are the primary forces that affect the state of the cannabis oil in your vape cartridge.


Temperature influences the viscosity of cannabis oil. The higher the temperature, the less viscous it is. If you leave your cartridge in a very hot car, this will cause the coil to absorb more oil which makes the cartridge look emptier. This practice is not recommended as the same forces of cohesion and adhesion may also cause the cartridge to start leaking. On the other hand, during cold weather, it is quite handy to have a vape cartridge in which the push-button batteries have a preheat capability.


Another force affecting how full your cartridge seems is pressure. If there is a frequent variation in the pressure during the manufacture and distribution of a vape cartridge, it will impact how full the cartridge appears. These pressure changes can have a deleterious effect on capillary action where it speeds it up in some cases and slows it down in others. This may also account for cartridge leakage.

In addition, once the wick has absorbed a large quantity of oil, if you try to add oil to the cartridge, there will not be enough air in the tank to allow you to vape. That is due to the impact of surface tension affecting the capillary action. This can also lead to cartridge leakage. 


The last force impacting how full your cartridge appears is humidity which directly impacts capillary action. The higher the humidity, the more capillary action will occur.


Inserting the mouthpiece onto a filled vape cartridge is known as capping.


Inserting a plug or silicone cap onto the mouthpiece and onto the base of the cartridge is known as sealing.

In order to stabilize the pressure inside the cartridge thereby retarding capillary action, it is very important to cap and seal the cartridges immediately after filling them.

How The Storage Angle Impacts The Wicking Material

Storing your cartridge upright with the mouthpiece on top will cause the filling level to appear lower. That is due to the impact of gravity on capillary action which speeds up the absorption of the wicking material.

Storing your cartridge upside down will cause gravity to prevent the occurrence of capillary action. This makes it likely that the oil may not be absorbed by the wicking material. Please be aware that when you turn it right side up, it will take some time for the oil to get to the coil. If you do not wait for this to happen, the result may be to burn out the coil while inhaling toxic fumes. This will make the oil taste burnt.

Storing your cartridge horizontally gives you a mixture of the aforementioned results.

Different Types of Extracts Affect Capillary Action

Oils with low viscosity means a faster absorption rate by the wicking material because of an increase in capillary action. Oils with high viscosity means a slower absorption rate due to a decrease in capillary action.

Cartridges Filled Based on Potency

Some companies fill the cartridges based on potency rather than volume. One particular company uses high technology machines with extreme accuracy capability to fill their cannabis vape cartridges with 350 mg of THC. They do this to guarantee more accurate dosing. In addition, different cannabis oils have different densities which affects the oil level in the cartridge. In other words, based on density, one cartridge may look like it contains more oil than another one of a different density.

Final Word

The rules and regulations  are very stringent in the medical cannabis industry when it comes to the accuracy of the contents and the labeling of any given product. I hope I have reassured you that you are not being shorted on the amount of cannabis oil in your vape cartridges.
Sources:, Why Don’t Vaping Cartridges Ever Appear Full?, Why Your Vape Is Not Filled All The Way, March 5