Step 4: Making spring holder and placing spring

Step 5: Making the "valve"

Now, cut a rectangle out of rubber. It should be some rubber that doesn't bend very easily. I used pipe sealing rubber. Its width should be bigger tha...

I have always been brewing in plastics bottles (not very professional, but for me it works without problems) and so I thought of some better way of getting CO2 out of the bottle and no oxygen in than capping the bottle and letting it squeeze when there's high pressure.
The liquid-filled airlocks are fine but making them is a horror and also, I was used to let bottles in cellar for long time until it's finished and sometimes I found out that it dried...
So there's one primitive airlock that needs no care.

It works just on two facts:
1)There's still higher pressure in the bottle than outside (this works until yeast dies or runs out of sugar)
2)Relative molecular weight of CO2 is 43.99 g/mol. Air has 25.93 g/mol. Result of this is when you have CO2 in bottle, it won't mix with air until wind blows into the bottle (at least for some time, due to diffusion).

Step 1: Materials

Step 2: Making the base

First, take the sand paper.
If the cap has some imprint on it, sand it down so the cap is flat.
In the middle of the cap, use the sand paper and make it rough. It should not be smooth.

Now we will drill three holes so that an M3 screw can be put in them.
One will be in middle and the other on opposite sides, place them near the inner cap circle.
Now, rip off anything overlapping off the holes.

Step 3: Placing screws

Now, put M3 screws in the outter holes with head down.
From top, put pads on them and then nuts.
Tighten until screws get partially inside the plastic (this will deform the plastic a bit).
This will ensure they will be air-tight.
Look at photos.

I use plastic bottles and I never came across any problem with it. No exploding bottles, no infection in wine. Just that several times I forgot the bottles closed and the yeast stopped working and living. (So far, the best ones are Sprite bottles, they have thick wall).

A poor man's airlock indeed. The poor guy wasted all that time and hardware making it when there's a cheaper (if you don't already have your hardware) and less complicated DIY airlock -

Cut a hole in your lidStick some clear plastic hose into the hole, but not so far that it touches your liquid.Stick the other end of the hose into a container of water that's lower than the top of your fermenting liquid.

Saved me plenty of times when I ran out of proper bubble airlocks (which are only $1.25 at most retailers)

I started making wine about48 years ago. The problem with the hose and water is that when the fermentation dies down and the barometric pressure changes the hose will suck contaminated water back into the wine. The commercial locks avoid that. I normally take a plastic grocery bag and put a piece of that either over the bottle with a light rubber band or in a bucket I put a trash bag over the bucket and a couple of turns of springy yarn. It has worked flawlessly for me EXCEPT when there were children, cats or puppies nearby who tore the plastic. I once saw a man who lived alone who made wine in jars and jugs. He put a flat piece of glass over the top and it worked well, but he was a recluse and lived alone.

We do the same for brewing beer - a wide roll of plastic wrap (lunch wrap, Glad Wrap, cling film, Saran Wrap) does the trick without any problems. The rubber ring seal taken from the fermenter's lid works to keep the plastic wrap in place. You can be sure it's sterile too, so if it falls onto the wort, no contamination.

Yes, I've tried this also. Might work even better, but in our country thin hoses are not sold everywhere and if you find some at hardware shop, they are made of silicone - so you can't glue them to the cap.And if you glue it, the smell of glue gets into your drink.Also, I wanted something that can't be easily broken.

to those of you who have offerd advice on diffrent substances to use in an air lock, or larger blow off tubes to larger bucket type airlocks?

y'all done missed the point ;)

the author of the 'ible 'expressed concern over airlocks evaporating off when "long term projects" are left to condition unmolested.

the purpose of an airlock is to allow the tank to out gas, and not let any outside gas enter into the vessel that could cause contamination.

this device allows pressure to build up, then release when sufficient back pressure builds up. So, more of a poor mans safety release valve than an airlock.

if you REALLY wanna go "poor man" about it.. just stick a balloon over the neck of the fermentation bottle for the same effect ;)

often times when we got a tank of brew, like say our barely wine, needs to hold at cellar temp for a period of say.... six months.. once fermentation is done we'll stick a butterfly valve on the tanks blow off tube and seal it off. At that point if any latent CO2 pressure builds up in the tank, the safety relief valve will let off until the tank equalizes to it the safety zone.. an added benefit of this is that before the tank lets off, a lot of CO2 returns to suspension, so at finishing time, carbonation is a matter of a mild adjustment rather then a full blown forced carbonation.

Excellent! I noticed you're in Czech Rep., it's probably difficult to locate "proper" airlocks there, and "food grade" probably just isn't available there, at least in the hardware store. I've had trouble occasionally with them drying out as well, especially with mead (honey wine). As a note, what you call "pads" are (at least in the US) called washers, the ones with ridges are called lock washers.

How about set a marble atop a rubber o-ring affixed to a small pinhole in the cap, use a bit of rigid tube to keep the marble from getting knocked off. More or less how I keep air from sucking back into my charcoal making buckets. Except I don't use an o-ring, just a dent with a hole at the bottom and a marble or heavy ball bearing.

here's how I do it and very very simple.Go to a store that carries tire valve stems. Drill a hole in the cap and pop in the valve stem. You can release co2 by just pushing on the stem valve like you do to let the air out of a tire or use it to inject gas..

Neat! As an alternative, what about those one-way check valves they use for car vacuum hoses? They're very small, and I don't know if they leak backwards over time. But they're cheap and may be available at car repair places. Worth a look, I suppose. Not sure what disadvantages it might have for this type of use.