Issues with attenuation

[Johow]

I have a couple of brews fermenting currently. One a stout that I pitched using a WLP090 1liter starter, on August 1st, 2 weeks ago today. I ferment in a temp controlled chest freezer and had started the fermentation at about 65 deg, and ramped is up slowly every couple days to 69deg. I was shooting for an fg around 1.017, though brewersfriend say it should be 1.013. After 2 weeks it is at 1.030. A couple of days ago, I added some things to the primary that may or may not have boosted the sugar level. I either didn't take an SG reading then or didn't write it down, memory fails me now. I added an oz of roasted coffee beans and 2 oz of Cacao nibs.
In general it seems to me that my fermentations are finishing at a higher fg than my Brewers software or recipes indicate. I've been using the SD super yeast lately for these beers in the new packaging from White Labs and though they say it is not necessary I have been making starters as well.
Another beer, a pale ale session beer started with an OG of 1.051(a little higher than intended cuz my efficiency was up) is at 1.018 after about the same time when the fg should be nearing 1.010. I'm thinking that this WLP090 should be doing better than this or maybe I'm just stalled.
Any advice for a better fermentation or should I just be more patient.

 

[dmtaylor]

Are you using a hydrometer or a refractometer?

If using a hydrometer, check the calibration -- does it read 1.000 in plain water? If not, you need to adjust all your measurements.

If using a refractometer, it works great for original gravity of wort, but it doesn't work right when there is alcohol present. For final gravity you have to adjust based on the following calculator:

http://seanterrill.com/2012/01/06/refractometer-calculator/

Those are the very first things to consider.

It is also entirely possible and likely that Brewer's Friend is just over-estimating the attenuation. Yeast is alive and they play by their own rules. What yeast did you use? What recipe?

 

[Johow]

I have both a hydrometer (yes, calibrated) and a refractometer. These measurements were done using the hydrometer. The yeast was White Labs WLP090 San Diego Super strain, my LHBS is about a block from my home and the yeast was refrigerated except for the time it took do drive that block. I made a starter for both of these brews overbuilding the starter and then using the overbuilt portion to build a starter for the second batch. So I made a 1.5 liter starter using this calculator overbuilding by 100 million cells and then poured off a pint of the finished starter and used it to build a starter for the second batch. The remainder of the first starter(now 1 litre) was chilled and decanted then allowed to warm to pitching temp(69deg) and pitched into the first batch(the stout) then when finished the second starter got the same treatment and was pitched into the 1.051 ale. Though I have never had my beers ferment quite as dry as the recipe specific, they were all pretty close except these two.
Guess it could be a bad batch of yeast. My LBHS is very concientious and carefull about storing their goods. All yeast and hops are refrigerated. They even offered dry ice which I didn't use since I was literally less than 5 minutes from my home.