Craft a Brew - Beer Brewing Kits & Supplies on Instagram: "“What’s with the bubbles?” Homebrewing Basics Part 3 Carbon Dioxide is a byproduct of fermentation, which creates bubbles and foam as it escapes through the airock. The CO2 also forms a protective layer above the beer, which prevents oxidation of your beer (which causes stale off-flavors). #homebrewing #homebrew #beerbrew #beerbrewing"