When I adopted proper aeration and a yeast starter, I decreased my lag time to roughly 12-14 hours.

Recently I bought Ferwraps and have been using them.

One night, I got the idea to apply the fermwrap after I put my wort in an ice bath, pitched the yeast, and affixed the airlock, under the impression that there was no need to wait for the wort to warm to room temperature. I went to bed immediately, and 8 hours later the airlock was bubbling.

The same lag time of 8 hours was noted when I did this again on the second time. I'll be brewing two more batches over the next 3 days and will note it again.

  • what's the temperature of the wort after chilling and then after warming?
    – mdma
    Commented Mar 9, 2014 at 20:23
  • @Mdma I leave it in an ice bath for a while -- perhaps an hour if not 1.5, and it is very cold to the touch. I warm it up to whatever the minimum optimum temperature for that particular yeast is -- in this case, 65*F and 64*F. Commented Mar 9, 2014 at 20:36
  • Why not just chill to your desired pitching temp, and then remove from the ice bath and pitch immediately? Commented Mar 10, 2014 at 21:49
  • Also, if you passively (and slowly) chill wort, you will lose one of the principal benefits of fast chilling, which is the formation and precipitation of "cold break" protein complexes. A good cold break will improve the clarity of your beer (and tannins that cause astringency also precipitate out with the cold break). "Active" chilling in an ice bath means stirring your wort as it chills with a sanitized spoon, and possibly stirring the ice bath with a separate spoon. Stirring prevents warmish layers of wort and ice water insulating the colder water from the hotter wort. Commented Mar 10, 2014 at 21:51

1 Answer 1


Yes, pitching yeast well below its optimum temperature and allowing it to rise will increase the lag time as opposed to pitching it at the optimum temperature.

One thing to avoid is pitching room temperature yeast into cold wort, or vice-versa. This will shock the yeast and potentially cause issues with fermentation depending on the extent of the temperature difference. This is why people advocate letting yeast warm up to room temperature and pitching at a very specific temperature. You may not notice much of an effect if it's a 10°F+/- variance, but anything extreme (e.g. room temperature to 40°F wort) may shock the yeast and endure a stunted fermentation.

Also, I'd be concerned about having the Fermwrap increase the wort temperature too rapidly. Have you measured how quickly it would take to go from very cold to optimal temperature? As a frame of reference, for lagering, it's often advised to slowly lower the temperature down to lagering temperatures (near freezing) at a rate of 1-2° a day.

  • Because I use yeast starters, which I refridgerate, I assume that I would want to pitch into wort which is as cold as that, correct? Commented Mar 13, 2014 at 4:13
  • Would you mind expanding on why increasing the wort temperature too rapidly would be a bad thing? I actually have some very precise measurements, let me see if I can get them for you. Commented Mar 13, 2014 at 4:13

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