Diacetyl rest for Wyeast 1968 London ESB

I brewed an all-grain Newcastle Brown Ale clone on Thursday, Dec. 19th (5 days ago). My OG was 1.046. I used Wyeast 1968 London ESB yeast.

My fermentation temps fluctuated between 64-68 F (stick on thermometer reading, NOT ambient), in accordance with the lower end of spectrum for the yeast's preferred temperature range.

This evening I took a gravity reading and it measured 1.014.

The yeast's website strongly recommends that I do a diacetyl rest for this yeast. So tonight I moved the fermentor out of my cool basement (both in temps and sauveness) and put it upstairs that has an ambient temperature of 73 F. There is still some airlock activity, albeit much less active.

Is this a wise move? Have I done that too soon? Is this an appropriate temperature for a diacetyl rest on this yeast? I'm hoping to bottle this bad boy sooner rather than later, so I hope now's the time. Thanks!

Diacetyl rest is usually done after 2/3 of fermentation (when fermentation is at its end but yeast are still active), so 5 days wasn't premature to do this.

diS said:

Diacetyl rest is usually done after 2/3 of fermentation (when fermentation is at its end but yeast are still active), so 5 days wasn't premature to do this.

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+1. Your good to go with the D-rest for 1968 at that temp. Since it's darn near finished, a 73*F room won't cause you any issues.

The temp bump will certainly help the diacetyl precursor (alpha acetolactate) go ahead and convert to diacetyl so that the yeast can convert it (to some other compounds that have such a high detection threshold you can't taste them in the amounts present).

My understanding of the optimal point at which to try to begin the d-rest is around 75-80% of the way from OG to expected FG.

I have had good results with ramping the temp up as soon as the airlock activity slows. I then leave it at the rest conditions, for the remainder of the fermentation.

Good stuff! Thanks guys! I'm looking forward to this brew.