The cartridge holds the liquid that is vaporized for inhalation. Observing bubbles in this liquid is frequent and usually indicates the device is functioning correctly. These small air pockets are a natural consequence of the physical processes involved in converting the liquid into vapor, and understanding their formation helps in managing the device and troubleshooting performance issues.
The Role of Air Displacement in Wicking
The primary reason bubbles appear is directly related to the wicking process, which moves liquid from the reservoir to the heating element. Inside the cartridge, the wicking material (often cotton or porous ceramic) draws the liquid toward the coil through capillary action. This action allows the liquid to travel through tiny channels, saturating the material around the heating element.
When the coil heats up, it vaporizes the absorbed liquid, rapidly decreasing the volume in that area. To replace this consumed volume, the saturated wicking material pulls in more liquid from the reservoir. This displacement within the sealed cartridge creates negative pressure, or a partial vacuum, inside the liquid chamber.
The pressure difference caused by the vaporization must be equalized by an intake of air to prevent the system from seizing up. Air enters the liquid through small intake channels, often near the base of the cartridge, and rises through the denser liquid as a bubble. This bubble effectively fills the space vacated by the liquid pulled into the wick. Therefore, seeing a small stream of bubbles after a draw is a sign of proper wicking saturation and successful air pressure equalization.
The intensity of the draw directly influences the speed and size of the bubble formation. A harder, faster inhalation vaporizes the liquid more rapidly and creates a stronger pressure drop, causing a larger bubble to form as the system rushes to displace the consumed volume. Conversely, slow, steady draws result in a constant, small flow of bubbles, confirming that the liquid is reaching the coil effectively and the internal pressure is being regulated correctly.
Identifying and Addressing Problem Bubbles
While a small number of bubbles is normal, issues arise when bubbles become trapped, too large, or prevent the liquid from reaching the heating element. This often leads to a “dry hit,” characterized by an unpleasant, burnt taste caused by the coil overheating the dry wick. The trapped air bubble acts as a physical barrier, blocking the liquid’s path to the coil’s intake ports.
Causes of Problem Bubbles
One common cause is a vacuum lock, where the pressure inside the cartridge drops too low, preventing air from entering to replace the consumed liquid. This occurs if the air channels are blocked or if the initial seal of the cartridge is too tight. The lack of air equalization effectively starves the wick. This leads to insufficient saturation and the resulting dry hit.
Another issue is improper initial saturation, or priming, of the wick, especially after a refill or when using a new cartridge. If the wick is not fully saturated before the first use, large air pockets can be trapped near the coil, hindering the flow of liquid. Furthermore, residue buildup on the wick or coil, often from sweeteners, can clog the tiny capillary channels. This clogging prevents the smooth flow of both liquid and necessary air bubbles, leading to inconsistent performance.
Addressing Trapped Bubbles
To address existing problem bubbles, a gentle approach is often effective. Lightly tapping the side of the cartridge can help dislodge a trapped air pocket, allowing it to rise to the surface. Applying gentle warmth by holding the cartridge can also reduce the viscosity of the liquid, making it easier for the air bubbles to move upward and escape. For a vacuum lock, a quick, light inhale without activating the heating element can sometimes create enough suction to break the seal and draw the air bubble away from the wick.
User Techniques for Optimized Airflow
Operational habits play a significant role in managing bubble formation and ensuring consistent performance. The intensity and duration of the draw, or puffing technique, is one of the most adjustable factors. Taking slow, steady, and shorter draws minimizes the rapid pressure drop that causes large, disruptive air bubbles. Hard, forceful pulls create a high negative pressure that generates excessive bubbles and potentially draws unvaporized liquid into the airway.
Proper filling technique, when applicable, is also important for preventing air-related problems. When refilling an open-system cartridge, tilting the device slightly helps the liquid settle and allows trapped air to escape before the cap is sealed. Overfilling increases internal pressure, making it harder for air to flow smoothly and creating a risk of leakage or a vacuum lock upon sealing.
Environmental factors, particularly temperature changes, influence the internal pressure dynamics of a sealed cartridge. E-liquids expand when warm and contract when cold, and this change in volume affects the pressure inside the device.
Moving a cartridge from a cold outdoor environment to a warm indoor space can cause the liquid to expand, which may push air out and then draw air back in upon cooling. This leads to sudden or persistent bubble formation. Storing the device upright in a consistently cool, room-temperature environment helps to maintain stable pressure and reduces the likelihood of air pockets forming unexpectedly.