When is it necessary to add yeast at bottling time? I have a dubbel that I will bottle after 2 weeks in primary and 3 weeks in secondary. Should I add extra yeast and, if so, how much? My last brew was a Saison which I bottled after about a combined 4 weeks of primary and secondary and it seems under-carbonated after 4 weeks in the bottle. This hasn't been a problem before, but I don't want to ruin the dubbel.