Missing OG.....

I just finished AG session #7 (Dude's Lake Walk Pale Ale). Since I got a Barley Crusher, my past 4 brews have hit 85% efficiency into the boiler consistently. I'm hitting my pre-boil volumes exactly as planned and calculated SG has been within a point every time. I also have figured out on my earlier brews how much trub loss/boil-off I have and other small losses to be able to hit my volume into fermenter spot-on. The problem I have is that my OG has been 5-6 points low on these past 4 brews which have otherwise had much better efficiency into the boiler. I use BeerSmith and have all the numbers plugged in for losses and it seems I hit my final volume fine each time. I just can't figure out why the gravity is off by so much. It's not a huge deal I guess as the beers are still fantastic but I'm baffled as to why this is happening. My initial thought is that I am not boiling off quite as much as I planned but that should leave me more volume into the fermenter which I am not getting. Thanks for any help!!

My first thought would be what temperature are you reading your hydrometer samples at? That can make a 3-6 pt difference if you're not adjusting, or if you're reading at way too high a temp. Aim to have your sample at 60-80 degrees and add one point for each 10 deg over 60 (hydro reading @ 70 deg is 1.055, therefore actual sample is 1.056).

Thanks for the reply. I actually take the readings at 60 degrees or thereabout.

since your mash target og is on, it only leaves boil off miscalculation, or trub loss miscalculation, no?

i add everything from my brewpot into a graduated bucket, so i get my volumes right on. pre boil to post boil.... i miss my target every time however. (beersmith estimated og) i am always 5-6 points low, so it has to be my technique.
sadly, i never have checked mashout gravity... i start my boil after i collect about 1 gallon of my fist runnings, so i cannot check after both sparges pre boil.

anyway, enough about me, back to you.

My first couple brews I had miscalculated my volumes since I made marks on one of my plastic spoons and used it as a dipstick once my kettle was filled but realized it was off by 1/2+ gallon. I then started using my graduated plastic buckets and measuring each runoff which is now pretty accurate.

have you measured the volume of trub left in the pot?
i use a collander, and pretty much whole hops always, so they make a good filter bed for hot break/cold break material.... i now have alot more into the fermentor than i used to when i racked from the kettle.

nosmatt said:

have you measured the volume of trub left in the pot?
i use a collander, and pretty much whole hops always, so they make a good filter bed for hot break/cold break material.... i now have alot more into the fermentor than i used to when i racked from the kettle.

Click to expand...

Yeah, I dump the remainder into a pitcher to measure and it has come out around 1 gallon each time. I was going to use a paint strainer today to see if I could salvage more of the wort but didn't. I drain from the valve on my pot through a stainless strainer and I just plan for a gallon loss....which it has been each time. Drain gets clogged at that point!