“Carb Tabs” are tablets used to bottle condition beer when a brewer does not want to fill a bottling bucket and add priming sugar to their brew. They are especially useful for small tasks like bottling for gifts or competitions, but are occasionally used by some to inoculate an entire batch. Even with today’s simplified counter-pressure fillers and beer “guns,” those who keg their beer also sometimes use carb tabs to authentically bottle condition select beers for aging.
A few companies currently produce carb tabs for the homebrew market, but unfortunately I haven’t had a very positive experience with any of them. Either the beer does not carbonate properly, off-flavors arise that were not there before the introduction of the tabs, or bits and pieces are found floating around in the finished product. And so, after having tolerated these issues for quite some time and becoming thoroughly irritated, I decided to try and make my own.
It took dozens of trials, but I finally arrived at a reliable method that is easy to accomplish and results in nicely conditioned beer. The process is just like making candy – essentially, you will need to heat up corn sugar until all of the water has evaporated, then pour the molten substance into a mold and cool until hard.
I use a small metal pot and the same digital thermometer that I use for mashing, which reads up to 350 degrees. If your thermometer does not go that high, you will need to purchase one that does. Also, you will need a mold that produces the right size tablets – I use a “mini ice cube tray” that just happens to have the exact right size receptacles for this purpose.
First, take some dextrose and dump it into your small metal pot with the heat on as high as it will go (I like to use about a cup or so – if you use too much it could cool faster than you can pour it into the mold). Add a few teaspoons of water while stirring continuously until the mixture begins to melt into a fluid state. After that there is no need to stir it anymore, simply stick your thermometer into the clear fluid and watch as the temperature rises. I suggest wearing a hot-mitt in case anything splashes up by accident.
As soon as the temperature gets above 300, shut off the heat and take the pot off of the burner. If you let the temperature get over 310, the sugar will start to caramelize and you will end up with a darker, harder product that is not only difficult to get out of the mold, but may add undesirable flavors to your beer. Next, let the liquid cool for a few minutes and then transfer into a Pyrex measuring cup. While the mixture is still fluid, transfer it into the ice cube tray and put the tray into the freezer to cool (Tip: I pre-cool my tray in the freezer for a few minutes to make the process faster).
After about 10 minutes you should be able to crack the carb drops out of the tray, but first you should prepare a bowl or plate of loose corn sugar. Your new carb tabs will be perfectly clear and hard, but they will also be sticky on the outside and if they touch each other they will be impossible to separate. That is why I suggest dropping them immediately onto a plate of sugar, which coats the outside and enables them to be easily handled for storage and use.
The entire process takes about 15 minutes and will produce carb tabs that work perfectly every time. No more floaters, no more flat beer, no more off-flavors – just nicely conditioned bottles without the fuss of measuring and mixing priming sugars.
Good luck and happy brewing!