I've stocked up on Grolsch bottles long time ago for storing fermented drinks (specifically kvas), but barely used them because of the need to deep clean them before and after every use. It would much better fit my schedule, if I could just prepare the bottles ahead when doing my regular housekeeping and have them ready whenever I need. I've read a bit about oven sterilization method and I want to try it, but I'm not completely sure I understand how it actually works or how should it be adjusted for a flip-top bottle.

  1. Do I need to take the rubber seal off before sanitizing and boil it or steam it separately? If true, how am I supposed to reapply it to the bottle without introducing microbes?
  2. How does the foil trick works? Do I just take a square of regular kitchen aluminum foil, wrap it around the neck an it magically shrinks to create a seal as it heats up?
  3. How do I create a seal for the cap, which also needs to remain sterile until bottling?
  4. If I'm wrong about the rubber seal and I can put the bottle as-is into the oven, would it be dangerous to sterilized closed bottles this way? This would be the easiest way to do it, but I don't won't to experiment with potentially exploding bottles.

The information on the internet seems to be really scarce (or I'm bad at searching), so I'd appreciated if I could get a step-by-step guide on what am I supposed to do. I'm following this guide by John Palmer for the method.


This is what I mean by a "foil trick", copied from the link above.

Some homebrewers bake their bottles using this method and thus always have a supply of clean sterile bottles. The opening of the bottle can be covered with a piece of aluminum foil prior to heating to prevent contamination after cooling and during storage. They will remain sterile indefinitely if kept wrapped.

2 Answers 2


I think it's worth mentioning that as homebrewers, we really need to be think about living in the "sanitization" realm rather than the "sterilization" realm. We have households, pets (and kids), hands, pollen, dust... All sort of ways for microscopic contaminents to land on, and in, our brewing equipment. It's impractical to try and keep things sterile since our homes simply are not sterile environments.

The phrase by Charlie Papazian: "Relax, Don’t Worry, Have a Homebrew" fits here. After all, homebrewing is a hobby. It's supposed to be mostly enjoyable or, relaxing. Sure, sometimes things go wrong but that comes with any hobby.

I've watched youtube videos and marveled at the excessively careful and precise process people have gone through to reuse/wash their yeast. Wash, boil, filter, transfer sometimes doing it over and over. I've also seen videos of one guy just dump part of the trub straight from one fermenter into a new batch of wort and said he's been doing it that way for like a year. He enjoys his brews. Point being, there is a wide spectrum of process here but apparently quite a bit of wiggle room as far as sanitary/sterile goes. Yeast, given a good head start, will do a good job of out-competing other organisms. Make sure you equipment is clean. I know people who have assumed Starsan is a cleaner. It is not, so make sure whatever comes in contact with your brew is cleaned with PBW or something similar after every use and you'll be way ahead of the game.

I'm not sure about the "foil trick". What I've seen is people wrap foil around a beaker of yeast when making a starter. This is to presumably lessen the amount of contaminent that gets in. It is not an airtight seal. If it were, there is risk of the beaker exploding as the yeast produce co2 as they ferment the sugars.

What I do with my swing top bottles is soak them in a solution of hot water and (unscented) Oxi-clean for about 30 minutes, gaskets and all, and then rinse them with cold water thoroughly. Afterwards, I'll put about 2 TBSP of Starsan solution in them, shake and seal. When I want to use the bottle, I'll dump out what's in there and put fresh solution in, shake and fill. I only use RO water for my Starsan and make a 5 gallon bucket of it. I used to filter my tap water for it but it would get cloudy and funky smelling after a month or so so switched to RO. The RO based solution never seems to get cloudy or funky smelling but I do dump it after 6 or 8 weeks. I re-use my yeast now using a mason jar and the same method. I always make a starter. If it doesn't act right, or smells off, I dump it. The last batch of yeast I brewed with was the 7th generation of some wlp002. It was fine. Beer turned out great. I get nothing but compliments on it.

I'm not about to argue with Palmer's writing, but I'm not on board with bleach (at the link above). I think it's unecessary and can cause big problems for your entire brew process if you don't get it all rinsed off completely.

If you still feel better using the oven, I would definitely take the rubber seals off and not leave the bottles sealed.

  • I edited my question to explain what i mean by "foil trick". I was fresh after searching on the internet for answers, so I assumed everyone will know what I'm talking about, when I say "oven sterilization method". Your answer gives an impression of a seasoned brewer, so I understand why soaking 30 min and 5 gallon buckets of cleaning solutions make sense to you. All I need is three clean bottles, ready to use whenever I want and I can easily fit three bottles in an oven. Today I sterilized some nasty jars using this method and I forgot I was doing it until it finished, it was so hands-off. Nov 19, 2022 at 16:32
  • Definitely take off the rubber seals or the flip-tops before putting the bottles in the oven.
    – chthon
    Nov 19, 2022 at 16:47

Don't fear the bleach, you don't need to add much. But to rinse it off, always use a metabisulfite solution (Campden). I always clean my bottles in a light chlorinated alkaline solution, then rinse them in mentioned metabisulphite solution. The advantage is that you can use the same solution to clean the fliptops, then seal your bottles.

But if you use the oven, never use it for any kind of rubber rings, they will dry out and not seal properly anymore.

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