Wyeast 3724 strain: what does it actually do

This is purported to be the famous Saison Dupont yeast strain, and there are few other brewers’ yeast strains out there that have generated more discussion in homebrew forums. It is said to behave differently than most yeast strains, specifically, it is notorious for a fast, aggressive start, only to “stall” at about 1.035 gravity, then continue working very slowly till final gravity is reached. Wyeast themselves point this out in their website and advise that it will finish, given time, temperature, and patience, and create that wonderful saison character.
But what exactly does that stall or slowdown mean? How long does it take?  And what temperature? And how much activity should you see during this “stall”? Since my fermentation setup allows for easy control of the various parameters and easy gravity checks, I thought I’d share the details in case it helps answer some of your questions.

The recipe
This was a lavender saison recipe. The grain bill was 6lb German pilsner malt, 4lb German Vienna malt, and 1lb of German pale wheat malt. Boil additions were 1 oz of Czech Saaz hop pellets at 60 min, 1 oz of Czech Saaz at 15 min along with 1 oz culinary lavender, and 1 oz of UK Fuggles at 1 min. Calculated IBU’s were 17.2. The grains were mashed at 152°F for one hour, and the volume of the wort was 6.7 gal at the beginning of a 60 min boil. After losses to trub, hot and cold break, pump, hoses, etc. 5.3 gal of wort were transferred into the fermentor. The yeast, of course, was Wyeast Belgian Saison 3724, using a 0.8 liter starter with 2.7 oz of light pilsner DME, on a stir plate. OG was 1.054. The wort in the fermentor was aerated using pure oxygen for 20 seconds via a carb stone.
The fermentor setup
Fermentation was done in a Vessi Fermentor which is both pressure and temperature control capable. Fermentation temperatures can be controlled accurately via cooling and/or heating in the range of 35°F to 80°F. A Tilt Hydrometer was placed in the fermenter which uses a wireless signal to communicate with a smartphone app so gravity measurements are possible at any time without having to draw a sample. The wort was cooled to 76°F and fermentor was set to that same temperature for the first 12 hours of fermentation, then increased to 80°F, where it was kept till the last few days. The pressure relief valve was set to open so that no pressure built up during fermentation, as this strain is said to be very sensitive to pressure.
The results
True to its reputation, the yeast took off really quickly, with airlock activity evident within 6 hours of pitch, and becoming really active over the first 24-36 hours. Starting at 1.054, the gravity was down to 1.032 by hour 48. And then it slowed down. Way down. One airlock bubble every 20 sec slow. So I had reached that “stall”. Except this is the wrong word for it. A stall implies that the yeast has quit working and has probably flocculated, giving up the job. That’s not true of this yeast. It just starts out like crazy then decides that a sprint is too tiring and slows down to a slow jog. OK, really a slow stroll through the park. But it doesn’t quit!
See the graph below for details, but basically what happened is that from day 2 after pitch to day 23 (so over the next three weeks) the gravity dropped from 1.032 to 1.016, in other words, less than one gravity point per day. At that point, on day 23, the yeast seems to have rallied somewhat, picking up the pace a bit, and dropping 8 more points of gravity over the next 6 days, down to 1.008. From there, I let it settle to its finish over the next few days, while I gradually lowered the fermentor’s set temperature down to 35°F, and clarified via several bottom port trub dumps. My final gravity reading was 1.007 at the time of kegging.
Wyeast 3724 fermentation graph
The beer is delicious! Has all the yeast character described in a great saison and if you don’t mind the nail biting (“will it drop another gravity point by tomorrow or has it quit????”), not to mention waiting for 5 weeks to get to the finished beer, then I’d definitely say this yeast strain is worth it. This beer (I call it “Emily”) certainly came out better with this yeast than previous versions I brewed with much faster acting but ultimately less complex and satisfying yeast strains. Say “hi” to Emily:
Emily beer

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