r/Homebrewing • u/KikoValdez • Sep 08 '26

Equipment Oven as an adequate method of sterilising a demijohn?

I'm looking to brew a small test batch (think 1l or even less) of alcohol and I'm having issues with how I would go about sterilising my vessel (the vessel I want to use is a 1l or 1.5l demijohn without braiding).

The biggest issue with sterilisation is the fact that I can't seem to find starsan in small enough quantities for sale that would fit my experimental needs and the starsan on sale in quantities of a litre and more costs around 40$ per bottle, which is an insane price and would be more expensive than the rest of the project combined.

I was therefore thinking about whether I could sterilise my demijohn by first rinsing it in warm water, then placing it in a cold oven and heating it up to 100 or 120°c to sterilise it by heat. I understand that glass and heat changes don't really like eachother, but I already have experience with putting ikea glass bottles in my dishwasher and then baking them in an oven and they withstood it just fine.

Does anyone here have experience with using an over for sterilising? If yes, would you recommend it?

6 Upvotes

72% Upvoted

36 comments sorted by

16

u/notguiltybrewing Sep 08 '26

You don't need to sterilize the fermenter you need to clean and sanitize it.

1

u/KikoValdez Sep 08 '26

What's the difference between sterilisation and sanitisation? I thought that in this context they were interchangeable

3

u/themorganator4 Sep 08 '26

Sanitation = removing all visible dirt and giving it a through clean but some pathogens may remain (although very unlikely to cause issues)

Sterilisation = the above but also removing/deactivating all pathogens entirely.

Sterilisation is pointless because (unless you are brewing in a controlled sterile environment wearing a sterile hasmat suit and all ingredients are themselves sterile), a small amount of pathogens will inevitably get in

11

u/lifeinrednblack Pro Sep 08 '26 edited Sep 08 '26

Super small point of clarification (sense we're already down a semantics rabbit hole) cleaning all visible dirt wouldn't technically speaking be part of sanitisation.

Cleaning = removing visible dirt

Sanitization = killing almost everythibg so that your microbes can out compete whatevers left over

Sterilization = killing all forms of life.

You're correct that sterilization isn't worth it unless you're dealing with mixed ferm bacteria and sta1+ yeast. In which case you be sterilizing your equipment afterwards

2

u/edman007 Sep 08 '26

Even with weird yeasts, you still don't need to sterilize. If you brew a wild sour you might have loads of interesting things in it that can infect a brew, and starsan probably won't cut it for sanitizing. However a dunk in boiling water probably will be just fine, that will kill all yeast and all known things that will infect your brew.

It's not however sterilization, because botulism spores will not be killed. Botulism however won't infect your brew because it can't deal with low pH.

1

u/Gerrit-MHR Sep 09 '26

Along these lines, we keep our stuff clean and then prior to using rinse with a strong KMS solution. .5 Tbl/ gal

2

u/Unfair-Corner6038 Sep 09 '26

Sterilisation is pointless because (unless you are brewing in a controlled sterile environment wearing a sterile hasmat suit and all ingredients are themselves sterile), a small amount of pathogens will inevitably get in

Please let me drop my two cents. It's all about that amount of pathogens. Pathogens are everywhere around indeed, and only way to prevent contamination(and sickness) is keeping that amount small. There's a threshold under which microorganisms can't thrive and colonize. Statistics and contr-measures. One patho cell is almost never lucky enough to build a colony, but billion is capable quite easily.

That's why i sterilize everything, down to cutter's blades used to open dry yeast packet. Better safe than sorry.

1

u/themorganator4 Sep 09 '26 edited Sep 09 '26

Of course.

Its down to each individual how far you go, the less pathogens the better.

I sanitise with chemsan, my equipment is already visibly clean but I wouldn't sterilise everything

11

u/BattledroidE Sep 08 '26

Counter argument: Star san will last you YEARS, you'll have to buy it once. You can reuse the solution for a good while. It's very cheap from that perspective.

Whatever you do, make sure glass heats and cools gradually. In the oven, I'd leave it until it cools down, don't even open the door. If it's not pyrex, it's not made for high heat, it's very sensitive.

7

u/AJ_in_SF_Bay Sep 08 '26

I looked you up on Reddit as it seems from the details that you might be EU, and I was right, I think you're in Czechia, which I believe is what we call the Czech Republic here in the US.

I know that many people, myself including, use and discuss Star San on this forum.

You may or may not know that Star San is harder to find in small consumer bottles in Czechia due to EU import regulations on its specific formulation, but it is my understanding (unless someone here corrects me!) the closest direct equivalent, Chemipro SAN, is widely available in smaller sizes (250 ml and 500 ml) in the EU. I did some online searches, and it seems available from Czech homebrewing e-shops like VasePivo.cz. Or maybe there's a local homebrew store (LHBS) near you that has the alternative chemical for cheaper.

Best of luck! I hope to make it to the Czech Republic one day. An old friend still has family there, abd I've enjoyed holiday traditions and heard fun stories (many beer-related). Cheers!

1

u/vdWcontact Sep 09 '26

Damn what a helpful post.

3

u/Available_Bad4381 Sep 08 '26

Glass is weird with heat, but if you've already done it with ikea bottles and they survived, you're probably fine. The main risk is thermal shock so putting it in a cold oven and letting it heat up gradually is the right call.

Just keep in mind that dry heat takes longer to sterilize than steam. I think 120°c for an hour should do it for a small demijohn.

3

u/idrawinmargins Sep 08 '26

Pbw to clean and starsan to sanitize. No need to sterilize your container. Just use the pbw to get any caked on debris off, then rinse out with water after. After that use starsan to sanitize the vessel.

3

u/Virtblue Sep 08 '26 edited Sep 08 '26

Use iodine(iodophor), don't use the oven odds are it will shatter.

2

u/idrawinmargins Sep 08 '26

New fear unlocked. A broken glass object in a oven would not be fun to clean out.

1

u/Wonderful_Bear554 Sep 08 '26

I did sterilise glass bottles in oven many times, but I used temperature closer to 200 °C. I used to put some thin foil on top of the bottle so it would keep sterile even I would bottle the next day only. There are risk that bottle can crack due to pressure, but I never had problems.  If you plan to brew in the future, starsan might be good option too, you can mix it with distil water and reuse, one bottle can last few years.

2

u/fitbrewster Sep 08 '26

You only need to clean and sanitize your vessel. No need to sterilize it. And definitely wouldn’t go through the trouble and risk of putting a glass vessel in the oven.

3

u/ExaminationKlutzy194 Beginner Sep 08 '26

Bleach water solution then rinse clean?

1

u/zero_dr00l Sep 08 '26

No dishwasher with a Sani setting?

2

u/KikoValdez Sep 08 '26

I've got a dishwasher but the maximum temperature it goes to is 65°c.

2

u/zero_dr00l Sep 08 '26

I mean some of the hicks in my area will absolutely just use bleach. I would rinse well with distilled water if you go this route (and probably best to seek other options).

1

u/homebrewfinds Blogger - Advanced Sep 08 '26

That sounds a little difficult and dangerous. Star San is almost free when you use the spray bottle method https://www.homebrewfinds.com/tip-using-star-san-in-spray-bottle/

1

u/KikoValdez Sep 09 '26

The issue is that starsan is essentially unobtainium in both price and stock and I don't plan to actually homebrew later in the future.

1

u/homebrewfinds Blogger - Advanced Sep 09 '26

Ah, makes sense. In that case, personally, I would use either boiling water (careful!) or a properly diluted bleach solution. I can't remember what the rate is but I recall an old podcast where Charlie from Five Star gave a dosing rate that he said at the time was a no-rinse bleach solution. To be safe you could use a properly diluted bleach solution and then do a sanitized water rinse. I would just be concerned about putting glass in the oven. Cheers!

1

u/KikoValdez Sep 09 '26

Right now I'm considering a hydrogen peroxide sanitisation. I'm just confused as to how I should do it. Should I just pour some in, shake it around, let it sit and then dump it out?

1

u/frozennorthfruit Sep 08 '26

I am still using my bottle of Starsan I bought in 2011. $20 original price. $1.33 per year so far with ZERO spoiled fermentation's. And I have used perhaps 20%. I figure it will end up being a lifetime supply.

Loosing even 1 batch every 2-3 years would have you wishing you spent the money. That said, see if you have any local homebrewing clubs in the area. Find a glass container, label it well and buy some off someone.

1

u/[deleted] Sep 09 '26

take my upvote

1

u/vdWcontact Sep 09 '26

Honestly wash it with dawn, rinse it well, dry in a warm oven, you will be fine most of the time.

1

u/allowishus2 Sep 09 '26

You can absolutely use your oven to sterilize any glass bottle that you can fit inside. It's my preferred method for sterilizing bottles.

This is the method I use from How to Brew

Put a peice of aluminum foil over the top then place the bottle in a cold oven. Increase the temp slowly, about 3 C per minute to 170c, bake for 1 hour. Turn off the oven and let it cool overnight, then take the bottle out when its cool. It will stay sterile as long as the aluminum foil is there.

If you want to bake cooler, you will need to bake longer. According to How to Brew:

170c - 60 min

160c - 120 min

150c - 150 min

140c - 180 min

121c - 12 hours.

1

u/Indian_villager Sep 09 '26

You could just wash it out with soap and then rinse with vodka.

1

u/hermes_psychopomp Sep 09 '26

Others have weighed in on whether this is worthwhile. I don't feel the need to add to that discourse.

However, I personally know somebody that DOES use his oven to sterilize his glass carboys. He understands that for the most part, this is unnecessary, but does it anyway. However when working with brett or other sour strains that can be hard to kill off, it can be handy.

If you want to do it, it'll work. Most of the time you'll be able to get by with thorough cleaning and a sanitization rinse.

0

u/Unfair-Corner6038 Sep 08 '26

Couldn't you use hydrogen peroxide 3% solution as a sterilization option? Isn't it more readily available than starsan?

Glass endures heat pretty well, way above 120C, it was created by heat in the first place.

Just make sure it's really clean before heating, or there will be leftovers of all what was invisible inside.

1

u/KikoValdez Sep 08 '26

I could use it, in fact I have some at home for washing clothes. I suspect that I'll need to rinse it thoroughly afterwards though, right?

1

u/psychoCMYK Sep 08 '26

not really. if you dump it out well, what's left won't be at high enough concentrations to interfere with your brew nor be toxic. it breaks down into water and oxygen anyways, and yeast requires oxygen in the first stages of fermentation

1

u/Hobby_boy Sep 10 '26

Did a bit of research and I found out you can get VWP in Czechia, which is a combined cleaner/steriliser.

On Pivoteka (a Czech homebrew shop), you can get a small 100g tub for the equivalent of £5.50 with the delivery included.

This stuff is also useful for cleaning stains from the inside of mugs, so it does have uses outside of homebrewing.