What happened?

[ArtCox]

After 2 weeks in the primary and no visible sign of fermentation, I moved my Excelsior Altbier to the secondary and it started fermenting again, nothing radical, but I have activity in the Airlock. Is this normal?

[psfred]

it happens. I suspect that as the yeast sediments, the beer becomes stratified and there are some sugars that the yeast can ferment but are not in contact with yeast, so when you mix it up, you get a bit of fermentation.

There is also quite a bit of carbon dioxide dissolved in the beer, and it will come out of solution when you transfer it. Looks like fermentation but isn't. This is a good thing, as it will purge oxygen from the head space.

Peter

[BM1]

I had some wort recently that appeared to be finished @ 1.013,expected FG was 1.012.I dry hopped it began bubbling again,steadily ( 1-2 bubbles/minute ) for ~3 more days and finished @ 1.009.I guess the hop addition had a stirring effect,or something.I don't rack to secondary,so I'm thinking that it might be good practice (from now on) to just give it a little swirl towards the end.Maybe I sped up the process a little.
Sometimes,air lock activity is very slow and may not be perceptible.
Always check the FG over 3-4 days before bottling.