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Seeker of Knowledge, and Homebrew
Jul 18, 2021
Reaction score
Cleveland, Ohio, United States
Dear HBT community,

This is my first post and of course it is a problem related to brewing! I am currently fermenting a Marzen beer for my Oktoberfest party and started performing my diacetyl rest for the WLP830 strain White Labs German Lager Yeast I used. Sadly I had to start my diacetyl rest the same day I left for a music fest and was not able to closely monitor the fridge temperature for 2.5 days. My fridge does not control temperatures all that well near the lager temperatures and sort of cuts out at around diacetyl rest temperatures (~65 degrees). I set the fridge setting and monitored the temperature for an hour or so until I thought the fridge kicked on, which now that I have returned and looked at the thermometer data, it shows that the fridge never went on and the ambient fridge temperature was at a whopping 75 degrees F.

Does anyone have experience that they can lend in relation to high diacetyl rest temperatures and how this is going to impact my finished beer?

Attached are copies of my recipe and notes that I used in BeerSmith, my fermentation profile from BeerSmith, a screenshot of the data that I input into the fermentation tab on BeerSmith, and an Excel spreadsheet I am using to track the fridge and fermentation data. Apparently I am not able to attach an excel file to a forum post, so in its place is am image of the compiled data in chart form.

Sorry in advance for the lengthy BeerSmith recipe print out, I have gotten in the habit of taking copious notes. For your reference I plan on bottle conditioning the beer for 3-4 weeks and cold storing for 3-4 weeks, and cold crashing with the remainder of time I have to be ready for the party on 10/2/21.

Thank You in Advance for Your Input,


  • McTaggart's Oktoberfest V.4 - Fermentation Data Chart.png
    McTaggart's Oktoberfest V.4 - Fermentation Data Chart.png
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  • McTaggart's Oktoberfest V.4 - Fermentaiton Profile.pdf
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  • McTaggart's Oktoberfest V.4 - Recipe & Notes.pdf
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  • Screen Shot 2021-07-26 at 3.37.16 PM.png
    Screen Shot 2021-07-26 at 3.37.16 PM.png
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I haven't reviewed your attachments, but a diacetyl rest that reached 75F for a couple days, rather than your 68F target, isn't going to hurt much IMO. Very slightly faster staling reactions is the worst thing I can imagine here.
I've started making lagers at room temperature ~70 F (with yeasts like S-189, S-23, WLP940, etc.). I've found that I have fewer problems overall, including zero diacetyl. I'd say you're in great shape keeping the temperature warm for a week or two or whatever. No worries at all whatsoever.
Thanks for the feedback, you both have eased my woes

I ended up doing a procedure explained in Yeast: The Practical Guide to Beer Fermentation by Chris White and Jamil Zainasheff on p. 223 called a Diacetyl Force.

Hot water bath Sample 1 of fermented wort in 160 degree F water for 20 minutes. Return Sample 1 to fresh Sample 2 fermented wort temp and smell and taste Sample 1 and Sample 2 for precursors and diacetyl.

I didn't notice any aroma nor flavor of diacetyl, but the heated Sample 1 did have a slightly higher slick mouthfeel. I'm going to chuck it to my bias perception and hold it in Diacetyl Rest for 1-1.5 more days and begin to cold crash.