Hitting Target Gravity

[callisbeers]

Last couple of times brewing I have overshot my target gravity. I will take a reading with a refractometer prior to boil. I have been low so I calculated out how much DME I needed to add in order to be at target after the boil. However, each time I have been a good 5-10 gravity points over target. What could be causing this?

 

[billl]

User error. Sugar doesn't magically appear.

Could you post your last calculations? volumes, gravity, temps, time in the process where they were taken.

 

[chickypad]

How are you calculating your "target gravity". If it's just from a recipe and the recipe is set for a different efficiency than you get on your system then you won't hit your numbers. If you have been keeping notes and measuring volumes accurately then you can figure out your average efficiency and adjust recipes accordingly. As billl said we need more info to help troubleshoot.

 

[callisbeers]

Last batch was a Kolsch with a target gravity of 1.044 (based on recipe entered into Brewtoad). Grain bill totaled 9.5 lbs. Mashed 3 gallons at 150 for 60 minutes, sparged 5.75 gallons for 40 minutes, pre-boil volume was 6.8 gallons. Took refractometer reading at 180 degrees and got OG of 1.025. Based on my calculations ( 44 Gu x 5.5 gal) - (25 GU x 6.8 gal ) / 45 Gu = 242 - 170 / 45 = 72/45 = 1.6 pounds of DME needed. I actually only added 1 pound. I then took a reading after boil at 70 degrees at got 1.052.

 

[billl]

I would suspect that your first measurement is off. Is yours an ATC refractometer? Was it stored need room temp or were you/it outside? Did you give it 30 seconds or so for the temp to equalize?

170 points would be very low efficiency on a 9.5 lb malt bill, so that is suspect.