I have only been doing all grain brewing for a few batches. I am using a kettle and 10 gal converted water cooler for the mash tun and doing a batch sparge in the same cooler. The OG was supposed to be 1.061 for the recipe I was using (an IPA) but I ended up with a 1.042.
Since many of you are more seasoned at this than me, what things can go wrong during the brew day that could result in lower original gravity? I can provide any other info that you might need, as the session was well documented. Thanks in advance!
You’ll get a lot of responses with what could go wrong. Before we get too far down the rabbit hole, can you post your grain bill and describe your mash/sparge process (including how much water you used in each and how much ended up in the kettle pre boil)?
1/ Too coarse a crush on the grains. Probably number 1 culprit.
2/ Volumes off - mash, sparge, preboil. Be sure to measure mash and sparge water accurately, account for grain absorption and dead space, and get an accurate boil off rate/hour on your kettle. This will help you hit your final volume into the fermenter accurately. If volumes are high or low, it affects your concentration of sugars and therefore your OG measurements.
3/ Temp accuracy - you need a thermometer that’s accurate enough to hit your mash temp fairly accurately. If you unknowingly are mashing too high or too low, you could be outside the optimal enzymatic range for good conversion.
Just another thing to look at, was your 1.042 before or after your boil? Silly question I know, but plugging that grist into beersmith for my typical 6 gallon batches, I get 1.048 pre-boil estimate at 7.66g, down to 6g into fermenter at 1.056. Changing volume to 5g into fermenter, I get 1.056 down to 1.068. Your 7.5 g boiled down to 5g should yield 5g at 1.063.
This was a big one for me until I started crushing my own grains. I’d get consistent mash efficiency for 3-4 batches and then all of a sudden I’d see a drop of 15-20%. As Denny has stated, “crush it until you’re scared” or if you have your LHBS do it, tell them to crush it until they’re scared.
My hunch is that the grains could be crushed more. Also, did you cool your wort to the temperature your hydrometer is calibrated to? Did you test your hydrometer for accuracy? It should be very close to 1.000 in water at the calibration temperature.
Do you really stir your mash in good, insuring no dough balls?
All these things can add up.
This was taken post boil, but I did take a pre-boil, which of course I don’t have on hand right now. I was really expecting to get much close to my numbers after this happened once already (as this time I was more diligent about temps, timing, and volume).
My grains were crushed at my local brew supply shop, and by all appearances look the way I have seen elsewhere. I ended up using the spent grains to make a great bread, so they weren’t so coarse that I couldn’t eat them comfortably. I will take that into consideration and ask for a finer crush next time (until I can assemble my own mill).
They probably won’t be thrilled with being asked to adjust their mill grind finer. But they likely won’t mind if you just ask them to double mill it (mill twice at their usual gap). I used to do that before I bought a mill - made a noticeable difference.
And to these I’ll add not adjusting the recipe for you system’s efficiency. I think #3 is the least likely. You’d have to be WAAAYYY off for that to matter.
Most of the suggestions here have to do with conversion efficiency, but your problem may have something to do with how you are sparging/lautering. Or it could be a combination of the two.
Good luck in troubleshooting and let us know if the problem persists.
I’m curious about one thing. Your strike volume was “about 20 quarts.” Then you added 8 quarts of 180F water, then you added another 18 quarts of water, and you let it sit in the tun for 30 minutes before draining? That’s 46 quarts, or 11.5 gallons in what I am assuming is a 10-gallon mash tun.
The thing that makes me think your volumes are off is the total amount of water you used. My recipe for a rye calls for 12.25 lbs of grain.