Grainfather missing OG

[Michael]

Morning all, interested to know what people do when they miss their OG. Do you boil down the wort more? Add sugar? Accept as is?
I’m on my 87th brew using a Grainfather. Early on I mostly hit my OG within a few points. Now I’m off more times than on target. For example, my OG today for a Dubbel should have been 1063, it came out at 1052. (Strangely last week I brewed a Pilsner with more than a kilo less grain than the Dubbel but came out with 1052 (on target) - the same as today).
Anyone out there using Grainfather having the same issues? Got to admit I don’t normally do pre- boil measurements…..if you’ve solved the problem what did you do differently?

 

[Unslaven]

Firstly make sure your measurements are consistent, and accurate.
Are you using the same gravity measurement device?
Are you measuring wort samples at the same temperature every time? (usual calibration temp is 20c.)
Have you checked calibration on your various temp probes?
Are you doing conversion tests?

Are you sparging at the same rate and/or are you performing vorlauf for long enough or maybe too fast thus channeling through your grain bed? This can be hard to test on a GrainFather/BrewZilla because you can't easily collect wort runoff samples during sparge to know if/when to cut the bed.

In regards to rectification, if it was pre boil measurement I would boil for longer, and then consider sugars/DME if necessary. This would allow you to keep consistent hop timings. Post boil, if it absolutely has to go in the fermenter you can really only consider adjuncts to 'fix' but realise this can then cause problems with varying final gravity.

The ideal fix would be to brew second batch at a higher gravity and blend the 2 to hit target OG. Then you would have twice the beer? Could even do an experiment with yeast/dryhop/ferm temp/PH to compare the 2.