Ridiculously high attenuation

[Beardedterror]

I brewed an English Barleywine a little over 2 weeks ago. I had an OG of 1.097, which was right on the money (thanks to my brand new refractometer). I just took my initial sample post-ferment, and I ended up with a gravity of 1.017, giving me an attenuation of around 83%. Usually, this wouldn't be an issue, but I used WLP002 (London ale yeast), which is supposed to be between 63-70%. I'm concerned that this is going to turn out much drier than I wanted it to be. What could I have done to have this active of a ferment?

I did make a good, healthy 2.5L starter for it. Fermentation temps never got above 68. I'm baffled.

P.S. I did drink the hydrometer jar. It tastes pretty good thus far, but there's a noticeable hotness to it from the alcohol. Will aging mellow out the alcohol flavor, or is it something I'll just have to deal with?

Thanks!
Beard

 

[BryceL]

What was your mash temp?

 

[Beardedterror]

What was your mash temp?

It came out a little HIGHER than I expected. I mashed between 157-155. Started at 157, ended at 155. I was aiming for 152, but I decided to leave it at 157 because I like a big mouth feel for most of my beers more than I like the simple sugars I would've gotten from lower temps.

 

[dcp27]

did you add much sugar? if not, sounds like you might need to calibrate your thermometer

 

[wildwest450]

did you add much sugar? if not, sounds like you might need to calibrate your thermometer

And or hydrometer. Something is a miss.

 

[helibrewer]

Did you calibrate your refractometer with distilled water first? What was your grain bill?

 

[wildwest450]

Oops didn't see it was a refractometer, you do know that they aren't really accurate for measuring alcohol, just sugars. There's a conversion chart you need to use.

 

[Beardedterror]

I took OG with a calibrated refractometer and hydrometer, FG with hydrometer. The numbers I got as my OG were within 2 points between the 2 tests, so I figured it was close enough. I did add a half a pound of molasses, but I don't think it would be enough to thin it out this much. I know something isn't quite right here, but I don't know what. My thermometer hasn't been calibrated in 3 batches, so that could be the issue, but I don't think it is. I had a good mash, and ended up with an 83% efficiency for the day (not too shabby). I honestly think it's just the yeast. I haven't worked with WLP002 before.

Here's the recipe:
16lb Mariss Otter
1lb Crystal 60l
.5lb Blackstrap Molasses
1oz Nugget hops 15.2% AA (60 min)
2.5l Starter for WLP002 (london ale yeast)

Process:
(BIAB) Mashed for 90 mins @ 157-155F, batch sparged @ 169F.
Boiled 2 hours, 1 hour no hops, 1 hour 1 oz nugget in hop sock.
Wort chiller used until temp hit 65F, siphoned to carboy, aerated via shaking, and pitched my starter.

 

[helibrewer]

That 1/2 pound of molasses might be enough to bring that attenuation up, I'm pretty sure it is close to 100% fermentable.