I brew my first lager and I have just started the diacetyl stage. I monitor the gravity with a Float device as well as the temperature. I fermented at about 12°C knowing that the yeast manufacturer recommends between 12 and 18°C.
Three days and a half ago, for the diacetyl rest I moved the fermentor in an atmosphere of about 19°C and let the temperature rose gradually for a little more than three days to reach 18.5 °C. The gravity curve has been flat for about 2 days now.
I notice that the air lock lets out a bubble every two minutes or so.
I’m not a chemist. My questions are:
Three days and a half ago, for the diacetyl rest I moved the fermentor in an atmosphere of about 19°C and let the temperature rose gradually for a little more than three days to reach 18.5 °C. The gravity curve has been flat for about 2 days now.
I notice that the air lock lets out a bubble every two minutes or so.
I’m not a chemist. My questions are:
- Does the transformation of diacetyl or other byproduct produce gas (carbonic or other)?
- Before I start the lagering rest, do I have to check that there are no more bubbles escaping from the air lock?
- Do the bubbles show that there is still unfermented sugar ? In other words does the gas come only from sugar fermentation ?