Trying To Avoid Undercarbing My 4th Batch

I've got my 4th batch fermenting downstairs and will be bottling either this weekend or next so I want to try to address a problem I had with my 3rd batch. Batch #4 is "Triple-X Sweet Stout" from the book "Brewing Classic Styles".

My 3rd batch was a 2 gallon batch of "Whose Your Taddy" Porter from the book "Brewing Classic Styles". I was aiming to carb to 2.0 volumes of CO2. I don't remember what calculator I used but I wrote in my notes that I used 1.2 oz of corn sugar. The beer tasted very good but was VERY under-carbed. Not sure why and I'd like some guidance as to what might have caused that and what I should do to avoid that again.

My 2nd batch was carbed pretty well though a bit on the low side. Batch #2 2 Gal Irish Red and I didn't write down how much corn sugar I used but I would guess it was close to 1.2oz like I used for Batch #3 (but might have been a bit more). So let me tell you what was different about Batch #2 vs the low-carbed batch 3. The first big difference was #2 used dry yeast and #3 used liquid yeast (I'm certain I pitched proper amount). The second big difference was #2 was bottled after 2 weeks in the primary and #3 was bottled after 3 weeks in the primary. Could the issue have been that after 3 weeks in the primary there was not enough yeast left?

So... Batch #4 is dry yeast again. I pitched about 3/4 of a pack of S-04 that had been rehydrated. I looked at the carb calculator on Brewer's friend (which looks like it's values are a bit higher than what ever I used before) and it says for 2.0 volumes of CO2 at 68 F I should use 1.3 oz of corn sugar. It says to use 1.9 oz to get 2.5 volumes of CO2. So maybe split the difference to get a bit more than I had last time?

So what would you recommend that I do as far as 2 weeks vs 3 weeks in the fermentor and how much corn sugar?

 

Thanks Jack! I'll take your advice....

 

The 2 week vs 3 week question was about time in the fermentor -- just wondering if it was possible that after 3 weeks in the fermentor my yeast was no longer up to the task of carbonating.

As to the time I leave it carbing.... I waited at least 3 weeks at 70 F then put some in the fridge and left the others at around 68F and put a few in the fridge at a time. So I don't think it was lack of carb time.

 

Yes at room temp... 70F for about three weeks. No cold crashing.

 

Bottled today! I used the 1.8 oz of corn sugar as suggested above to get 2.4 vol in 2 Gal batch. I made it was well mixed during bottling. Bottles are now sitting at 72 F where they will sit for 3 weeks before I try the first one.

This was the smoothest bottling day I've had except for my first batch! Second batch I had trouble due to some bottles that had slightly too large opening. Third batch I had some bottles break - the capper that came with my kit seemed to not work so well! This batch I got a nice new red capper and that felt much smoother and all worked well. I also got one of those Fast Racks and that made things easy...

So thanks for the advice and now I wait!

 

Pretty sure I did.... When I looked at it all the sugar was dissolved.

 

Forgot to update you all on this. The carb level turned out OK... Could be a bit more but it is acceptable. So next time I'll bump things up just a bit more. Thanks for the help!!