Why is some of my beer flat (half of the bottles in one of 2 batches done together)?

Question

I brewed and subsequently bottled 2 batches of beer together, following much the same process for cleaning/sanitizing and brewing throughout. When bottling, I bulk primed both batches with a sugar solution split between them.

Having bottled both batches, one has come out fine with all bottles carbonated, but the other has about half the bottles with no activity.

I suspect the yeast might have died in that latter batch, or an oxygenation problem, but am seeking clarification and suggestions. The flat beer smells and tastes ok, it just hasn't carbonated.

Answer 1

If the latter batch had about half of the bottles uncarbonated like you mentioned "but the other has about half the bottles with no activity" then it sounds like the sugar solution and beer did not get mixed thoroughly and therefore the ones that didnt have enough of the sugar solution did not carbonate. To avoid this I put the sugar solution in my bottling bucket and then rack onto it also stirring lightly with the racking cane before bottling.

Answer 2

I agree with the other folks that you have to put your priming sugar in the bottling bucked prior to racking the beer over. Another thing to consider, though - any chance you boiled your bottle caps to sanitize them? If so, you may have damaged the seals which could explain your lack of carbonation.