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.

 

[Michael]

I posted a thank you last night but it doesn’t seem to have appeared and so “thank you” for this it is very helpful. I suppose the bottom line is there is no easy solution and I’m going to have to delve deeper. One question, I have a perforated plate atop the grain bed during sparging. Wouldn’t this prevent any channel formation?

 

[Unslaven]

I posted a thank you last night but it doesn’t seem to have appeared and so “thank you” for this it is very helpful. I suppose the bottom line is there is no easy solution and I’m going to have to delve deeper. One question, I have a perforated plate atop the grain bed during sparging. Wouldn’t this prevent any channel formation?

In my experience perf plates/sparge manifolds etc help to avoid digging holes in the top of the grain bed, which does help, but they cant really stop a channel formed though the bed by path of least resistance. That's why cutting the bed when the PH gets too high/SG too low on the runoff is a thing, and one of the uses for manometers on lauter tuns as you can see the pressure change during sparge. This is harder with a GF/BZ because you can't really measure from one point, or easily measure at all.

One point I had not considered in my original reply is the efficiency drop at higher grain bills. This shouldn't be affecting you as much as you stated (same OG with a kg more grain), but it does need to be taken into account in recipes. Somebody else with more GF experience can probably help here, but after as many brews as you have done I'm sure you have come across this.

You could try some rice hulls for bed flow in conjunction with a stronger vorlauf to compact the bed, then sparge as slowly as possible whilst always keeping water above the bed. I have found this can help, but too many hulls will make the problem worse as you will sparge too quickly.
Also maybe just cut your bed in a cross pattern with a knife/paddle 2/3 of the way through sparge, or even multiple times. Avoid the edges, as I have found on single vessels the sides of the pipe can be problems for channelling (more so with a perf plate). It might even be worth while removing the plate so you can see any obvious channels.

I would still start with your measurements. Wouldn't be surprised if after 87 brews your GF is not as accurate as it was, and make sure any gravity readings are done as close as possible to 20c. ATC is a lie. Don't trust it.
I use an ice water bath with a stainless milk frother jug to get wort down to temp as quickly as possible. Metal receptacle is key for maximum thermal conductivity and can go from boiling to 20c in about 30 seconds, vs 3-5 minutes in plastic. Ice is cheap to buy and cheaper to make.
Just don't measure PH in a metal jug.