Why has Brettanomyces in secondary formed pellicle but no attenuation after 6 weeks?

Question

My first beer with Brettanomyces.

I have brewed an Orval-like beer, OG 1.062, primary yeast WLP510 Bastogne Ale, and WLP650 Brettanomyces Bruxellensis as secondary yeast, pitched after 2 weeks in primary (SG 1.010 at pitching, after racking to secondary).

It has now been 6 weeks, and a thin but hole-free pellicle has formed, about week 3-4. I sampled the beer today, and while the flavor is nice, it has virtually no Brett character, and SG is still 1.010. Temperature is stable around 21 C.

I expected SG 1.004-1.006 at this time. What is wrong?

Answer 1

Wait longer, they'll wake up some day.

For comparison, my most recent brett beer got brett b in the primary, fermented out to 1.010 (typical for the other yeast) and then sat for two month doing nothing before the gravity dropped & flavors appeared. Ended up at 1.005. A bit of pellicle formed later, but I don't think pellicle formation tells you too much in this situation.

I also find the flavor will be better - less horsey - if you keep the beer a little cooler, like 65F/18C, but maybe its just because I waited so long for the ambient temp to drop.