How to Create an Airlock for Making Wine or Beer

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Keep your fermenting alcohol airtight

Reviewed by Sander Raav

Last Updated: September 5, 2023 Approved

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An airlock lets carbon dioxide (CO2) escape from fermenting wine and beer without letting outside air in.

Things You Should Know

Remove the label from and rinse out a prescription pill bottle. Then, drill an 1⁄8 inch (0.3 cm) hole in the cap.
Thread the tube of a ballpoint pen through the drilled hole, and seal it with epoxy. Place a clean rifle cartridge over the end of the pen inside the bottle.
Drill a hole in a cork slightly smaller than the pen tube, then thread the pen through the hole on the outside of the pill bottle. Fill the bottle with water, and place it in the carboy.

Steps

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Prescription pill bottles with the label removed work well.
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Insert the pen in the bottom hole of the pill bottle and push it in all but ¹⁄₂ inch (1.3 cm) from the top. Mix fast-curing two-part epoxy and seal the pen to the bottle.^{[2]
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Place it over the end of the pen inside of the pill bottle.
Place the end of the pen all the way through the cork.
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Community Q&A

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Question

What if I don't have a rifle cartridge? What else can I use?

Fear.of.moths

Community Answer

A sanitary piece of aluminum foil crimped over the top, or even a plastic baggy with a rubber band on the outside (either use a new roll/box or pour some of your favorite high proof liquor on it just to be sure) should do the trick.

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Question

If fermenting in a 5-gallon bucket, wouldn't surgical tubing, run from the bucket lid, with the end submerged in a jar of water serve the same purpose, still allowing it to " burp" without letting air in?

Daniel Herkes

Community Answer

Yes, it would. Years ago they placed the expiratory circuit on a mechanical ventilator in a flask of water for the same reason.

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Question

How do you make sure the rifle cartridge doesn't float and come off the pen tube?

Snakey006550

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To make sure the rifle cartridge stays securely attached to the pen tube, use a strong adhesive like epoxy or super glue designed for metal bonding. Clean the inside of the cartridge with alcohol or a degreaser to remove any dirt or oil, and lightly sand the interior to improve adhesion. Test-fit the pen tube to ensure a snug fit, and if it’s loose, wrap the tube with thin tape or use additional adhesive to fill gaps. Apply the adhesive evenly along the tube and insert it into the cartridge, making sure it sits securely. Hold or clamp the pieces together until the adhesive cures fully according to the instructions.

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Tips

The airlock works on the exact same principle that your bathroom sink does for the trap below the basin. It creates a pocket of air that can escape through the top, but doesn't allow air from above to enter. You can substitute any of these parts with similar items. Clear plastic bottles are easy to work with and it's important to see the bubbles in the water to know that your solution is fermenting properly. The CO2 goes up the pen and is then redirected below the water by flowing down the rifle cartridge and out the top of the pill bottle through the hole you drilled in the lid. A commercial airlock will do exactly the same thing and will cost you 10 to 20 dollars. With 10 minutes of work, you can make this for pennies.

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Warnings

Be sure to let the epoxy cure for an hour before filling with water.

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Check the water level in the airlock every few days to make sure it's high enough, as it evaporates slowly during this process. The bigger the pill bottle you use, the less you'll be adding water.

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