Problems Carbonating Ginger Beer

I'm brewing ginger beer following the Art of Fermentation and am this close to wild success. The only problem is that it won't carbonate right; opening the bottle gets a nice fooomp noise, but no fizz in the drink. So there's obviously carbon dioxide there, but...

I make the ginger bug with 1tbsp each of ginger and sugar. I boil up the ginger/sugar decoction just as the instructions suggest, waiting for it to cool until body temperature or cooler before adding the ginger bug. I wait a few days until it starts to fizz and bottle, letting sit a few days more to carbonate, then refrigerate.

Possible points of failure: I stir the mixture during the days it ferments before bottling. I thought that might knock the floating ginger bits back in and help it ferment, but maybe it's knocking carbon dioxide out? My carboy bottles are hand-me-downs - the seal could be imperfect. For people who've done this before, am I waiting too long to bottle and missing peak fermentation? I thought I did that once and might be bottling too soon.

Weirdly, the first time I did this, it fizzed appropriately (so the bottles probably aren't the problem). I'm on the fourth batch, each time trying to get more fizz, but have gotten none at all. This past batch was an attempt to do everything exactly the way I did it the first, most successful time, and nothing. I took notes and the first time, when things carbonated, the ginger beer only had to sit one day on the counter and was fizzy. This past time, I waited five days and only got the foomp.

My impression is that I need to wait longer until bottling. Does that sound right?

Hi Matheson, welcome to Permies!

Carbonation happens when enough CO2 gets suspended in a liquid, and then the CO2 will come out of suspension forming small bubbles on nucleation sites. Have you ever poured a carbonated drink, beer or soda, into a glass and then have it totally foam over, but it wasn't foaming over in the bottle? That happens from an abundance of nucleation sites in the glass allowing for lots of CO2 to come out of suspension immediately, from either scratches in the smooth glass, dust particles, or even from soap residue from washing and rinsing, like those water spots sometimes seen in glasses. This is how carbonation happens.

On to your brew that seems low in carbonation, and that is resulting from low amounts of CO2 in the liquid. The CO2 in there making carbonation comes from the microbes (yeasts) fermenting sugars. Without enough residual sugars when bottling, there will be poor or no carbonation. Too much residual sugars when bottling can result in exploding bottles, and I've had cases of exploding beer bottles back in my brewing days.

My impression is that I need to wait longer until bottling. Does that sound right?

This will have the opposite effect. Allowing it to sit longer before bottling will allow the yeasts to munch through more sugars, resulting in flat or still beverages. Sometimes still beverages are nice for the style, like some wines. But it sounds like you're after carbonation and mouthfeel. There are a couple ways to approach this. Bottle sooner, which means leaving more sugars still floating around that haven't been consumed by the yeasts, and that will make for more fizz. Another way is to allow fermentation to fully finish, then add sugars right at bottling, and this can allow for a measured amount of sugar giving a known amount of carbonation. Then you can tweak future batches, adding a little more or little less to achieve the level of carbonation you desire. Hope this helps!!

you can rescue this batch by doing a second fermentation (like you would with kombucha or when bottling beer), as James mentions- put it into sealed bottles with a priming sugar (could be fruit juice, a few raisins, etc or just a bit of sugar), seal it up, and let it go a day (for my cool house. if you live somewhere hot maybe less time) then refrigerate and enjoy. Make sure your bottles are tight and don't let them explode!!

The stirring will release the CO2.  That's what they do to wine to get rid of the CO2 before bottling, so I'd stop that.

I'm having the same trouble with ginger beer, rootbeer, and juices fermented and carbonated with ginger bug. The mixtures have tons of bubbles in the liquid, but no real carbonation. It does a light pop when I open the swing top bottles, but the resulting bubbly beverage tastes completely flat. I am so discouraged.