Monday, January 28, 2013

Forget Priming Bottles, Drink Your Homebrew Sooner With a Homemade Carbonator Cap

Homebrew bottle cap with schrader valve in it.
This post will show you how to carbonate individual bottles of mead, cider, soda or homebrew beer at any residual sugar level, any carbonation level and without having to wait three extra weeks to bottle conditioning with yeast. I am not a huge fan of dry mead or cider, but I do prefer to bottle my homebrewed cider with some residual sugar leftover, so how can I leave some sugar in but carbonate in the bottle without the yeast metabolizing all of my sugar? I had written a previous post about force carbonating without a keg, but this is alot less expensive than the $20 carbonator cap at my local homebrew shop. In the past I would have to backsweeten with a juice concentrate and let the yeast add carbonation in the sealed bottle. This post will show you how by adding a schrader valve you can skip the whole bottle priming process and go straight to forced carbonation any beverage of your choice.
This technique is really geared more towards 1 gallon brewers or people who frequently make small batches. I can see how constructing enough of these for a five gallon batch would be a pain in the ass! For me though I only have to make a few for my 1 gallon homebrew batches.

To do this the internal column of a hand bottling capper must be removed with a hacksaw to make room for the schrader valve while capping. So first we remove the walls on either side of the internal column to gain access to it and then remove it with a hacksaw. You will lose the magnetic bottom of the column that helps align the cap to the bottle. I have found that if careful this piece is not needed when bottling. I found that a dremel tool or cutting wheel attached to a hand drill work best.

Homebrew bottle capper unaltered.

Bottle capper with outer wall removed.
Note the internal column.
Internal column removed with hacksaw.

You may either punch a hole in your beer bottle cap by eyeballing it, or take a more exact approach and make a template to be used as many times as needed for a hole perfectly in the center of the cap everytime. Using Thales Theorem in reverse we can find the center of a bottle cap with just some paper and a pencil. Credit and a great instruction video for this theorem are here.

Take a quarter and place the corner of a piece of rigid paper over it. Using a pencil trace over the edge of the coin:
Next cut from one edge of the paper to the other right along the bottom of the curve of the coin outline:
Place the cut piece in a bottle cap and trim as needed until it fits perfectly inside the cap. Below is an image before I trimmed it to fit correctly:

Once trimmed, place over more paper and cut out a second triangle the exact same size. Place one atop the other and align the edges as shown. Take a piece of glue and adhere them to eachother:
Next using an exact-knife, scrap a tiny "dot" into the underside of the cap with the blade. This will be a mark to show you where to place your hole punch:
Punch a hole in the center of the cap from underneat hthe cap:
Using a step bit, drill a hole big enough to fit your schrader valve into(I used leather gloves, and so should you!). My valve was 7/16", and I think this is the correct size for the smaller outer diameter schrader valves:
Bottle cap with rough burrs.
We will get to those burrs in a moment, first lets remove and sharpen up the hole on the underneat hside of the bottle cap:

Finally we grind down the top of the cap to remove the burrs. A grinder would be best, but I only have a sharpening stone:
Here is the burr removed. Notice there is still a small lip, this actually aids in the stability of the cap:

Finally, insert your schrader valve into the bottle cap using pliers. I like to insert it as far as it will go, then use pliers to pull it from the top through the cap. Be careful not to damage the threading with the pliers!
Here is the finished product just prior to using the bottle capper:

I set my regulator to 55psi and let sit in 38 degrees F for three weeks as a bench test:
So by now you are probably wondering if this works right? You tell me:
Removing homemade carbonator cap.

Leave a comment!

Has anyone done anything similar to force carbonate homebrew, any thoughts on how to improve this? If so let me know!


  1. I like your paper/origami method. I would probably just eyeball it and punch through the cap. Though my version may not work like yours, or at all :)

    1. Ha, I had the same fear with this project. If you do this be sure to use the kind valve with a rubber base. A metal base will not fit. The proper name for these valves are, "bolt stem valves".

  2. Try doing this with a 2L bottle and the plastic screw cap. the cap will be reusable, and you get more beer faster. (a 2L is almost the same capacity as a 6 pack.

  3. With a screwtop beer bottle you would not need to destroy your hard-to-make cap...

    Kombucha bottles are glass and have as larger top (plastic) that could work with a stainless bolt on valve- see ebay " Tubeless stainless Tire Valve Stem straight"

    I am going to make my own Perlini-style drink shaker with a 1-1.5L Nalgene bottle and one of the valve stems (mentioned above)
    Similar to this design in concept and I will likely put the valve in the cap so I have a flat surface that is easier to get to and replaceable,if needed.

  4. I made a bunch of these with plastic PET bottle caps. They work a treat, are easier to make and more re-useable, and can be put on any size bottle. The only extra I had to get was silicone washers to replace the smelly black rubber ones that came with my valve stems. I use these to make 2L bottles of fizzy water too, and they are great for making sparkling wine from regular table wine.


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