high F.G.

my last 3 beers have been big beers with an O.G. of about 1.095.  I am starting with around 18 lbs of maris otter base malt and 5-7 pounds of other grain.  my strike water is at 165 which gets me to about 132 and I then heat it to 148-152.  I sparge at 170 F. I boil for 60-90 minutes.  I either pitch 2 vials of liquid yeast or have a 2500ml starter ready.  all 3 beers have stopped at about 1.045-1.035.  this has never been an issue before.  I have checked the calibration on my thermometers and I am using a refractometer that reads brix/gravity and it is calibrated.  Any ideas out there?

Are you using a calculator to convert the post ferm gravity?

Like Stevie asked, your refractometer gets thrown off in the presence of alcohol and the reading needs to be adjusted to get the correct FG.

no  I just got the refractometer.  what is the process to properly calculate it if you don’t mind me asking

I use Sean’s calculator

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

I suspect, and I think Sean has mentioned as well, that the accuracy of this calculator starts to fall off on higher gravity beers. I still use it and a refractometer for all my readings because I don’t really care what teh F.G. actually is so much as that I have reached it, unless I really want to know the actual ABV. then I use a hydrometer instead for F.G.

Use Sean Terrill’s calculator linked above, and you’ll get the right answers.

Also, just curious, what yeast are you fermenting with?

I am using California ale yeast, wheat yeast and thames valley yeast.  all from white labs.  I used the calculator and it still at 1.031 then  I have a starter going of super high gravity yeast from white labs and I hope that will ferment down to a proper FG

Before you add any other yeast, use that link above for the Sean Terrill calculator.  You HAVE to.  The refractometer does NOT REPORT FINAL GRAVITY PROPERLY in presence of alcohol!  It reads much higher than it should with alcohol in there.  You need to use the calculator to know what the final gravity REALLY is.

I did use the calculator and it says my gravity is still around 1.030.  I tried a sample and there is a lot of residual sugars in there. normally I have had no problem fermenting down to 1.012 for a big beer like this

Oops, missed that.  Alright, add more yeast and hope for the best.

and my apologies I was wrong with my final gravity reading.  it was actually around 10 brix not 14 like I thought.  so using the calculator its actually down to 1.008 or so.  so thanx for all your help guys.  now I have a yeast starter going, hmmm what should I do with it?  I will brew this weekend!!

Ha ha ha… perfect excuse to brew some more!  :smiley: