Diacetyl rests

[meirion658]

Brewing my first all grain lager and heard a lot about this diacetyl rest.

Currently the brew is brewing along at 11c in a brew fridge with a gravity reading of 1.034. OG was 1.047.

Yeats used was whitle labs mexican WLP940

Question is at what point do you start the rest 75% 50% etc I've heard so much conflicting information.

When the diacetyl rest start what temp should I aim for and how long to keep at that temperature

 

[foxbat]

If you've noticed that fermentation has started to noticeably slow down from its peak (usually about 5 days with a lager) then you can start to allow the temperature to free-rise to 16-18C and keep it there until it's completely done. I leave it there for a total of 3 weeks in the fermenter and then go straight to keg.

 

[SaintKel]

Typically with lagers I put them up to 15c as soon as I see them drop under 1.020. Usually let it sit at that until it hits FG.

 

[Dorst]

All yeasts create diacetyl during fermentation but they also clean it up at the end of fermentation. If your beer has diacetyl in it - you most likely packaged/bottled/kegged it too early. Lagers ferment at a lower temperature and thus work slower. It increased the chance to package before this cleaning up has happened.

I typically let my lagers free rise to about 18C for a day at the end of fermentation. The higher temperature promotes the yeast activity that is associated with the cleaning up of any residual diacetyl. Because fermentation has already taken place this has no impact on the flavour of the beer.