I'm having some trouble with English ale yeasts fully attenuating. I have an oatmeal stout, OG 1.050 that will not ferment below 1.020. It is mashed at 152, pH 5.40, fermented with 2 liter starter wlp002.
BCS brown porter mashed at 153, pH 5.40, 1 packet rehydrated S-04 yeast, OG 1.054, FG 1.022
BCS mild mashed at 152, pH 5.33, 2 week old vial wlp002, OG 1.038, FG 1.016
MO smash mashed at 152, pH 5.21, 2 liter starter wlp 002, OG 1.050, FG 1.020
My basic process for all: thermometer, pH meter, scale, refractometer, volumes are all calibrated. Mash time is 75 minutes, 60 minute boil, chill to 66f in ~15 minutes, oxygenate 60 seconds, pitch and allow to free rise to 68f, hold fermentation temperature at68 until fermentation activity begins to slow and raise temperature to 72 while rousing yeast twice a day until fermentation activity ceases.
I generally have no problem with my American ales fully attenuating, even big beers. But the English ales have been rather frustrating. I will try a fast ferment test on my next batch. Why can I not achieve better than 57-58% attenuation with English yeasts?
Thanks in advance for any suggestions.