One great thing about homebrewing is that you can reuse the same bottles again and again. But it’s important to keep them clean and make sure they’re properly sanitized before bottling. Get into the habit of holding your beer bottles up to a light to examine for deposits on the inside of the glass. Deposits will appear as a ring or as dots, often in the bottle’s neck. These spots are bacterial cultures and they are a clear sign of infection. The picture above is an example of a bottle where this infection has gotten way out of hand. Does that mean it’s no longer usable? Not at all!
Simple household chlorine bleach will solve this problem. You only need about 2 millilitres of bleach per litre of cool water to make an effective sanitizing solution. Fill your infected bottles with the solution or submerge the bottles into a basin/bucket/sink/bathtub (whatever works) and let them soak. You can leave them overnight but a couple hours of soaking should be sufficient to remove all bacterial deposits.
After the bottles are sanitized, you can cover the tops with some aluminum foil and they will remain sanitized until you’re ready to bottle. REMEMBER to rinse the bottles a few times with hot tap water to remove bleach residue before bottling.