How are air bubbles formed?
Air bubbles are formed while you are packing your jars with food or adding liquid (brine & syrup). Pockets of air become trapped inside, sometimes visible just by looking at the jar; other times they’re inconspicuous.
So what exactly can you use to remove air bubbles?
Pretty much anything thin enough to easily maneuver around the inside of the jar works well. Wooden and plastic utensils work best because they likely won’t scratch the jar and create any issues. AVOID using metal utensils for that reason. Scratching the jar could introduce bacteria or create other problems during processing.
Now that we know what to use, let's talk about how to properly remove air bubbles. After you’ve packed your jar with food, choose a tool to poke each side of the jar, pressing the contents gently towards the center. You may need to do this several times to allow air to rise to the surface. After an air bubble (or two) pops, the fill level will have dropped visibly because of the air that escaped. Top the jar back up with liquid or food to the recommended headspace for that food product. Wipe the rim clean. Then proceed to put the lids on and process your bubble-free jars.
Sources: https://rusticwise.com/how-to-remove-air-bubbles-when-canning/
https://www.healthycanning.com/debubbling/
