First all grain - low SG

[Rosshedley]

Hi Brewers,

I did my first all grain brew today using this BIAB 1 gallon recipe:
https://www.beercraftr.com/1-gallon-session-ipa-recipe/

My pre-boil SG should have been 1.065 (this is the same as 65 gravity points, right?) but was 1.023. Way out! (I adjusted the actual reading of 1.018 as temp of wort was 37oC).

What could have gone wrong?

I did have trouble maintaining temp of mash at 67oC. I checked every 15 mins and had to give it a blast of heat to raise again, and I expect it dropped fairly quickly each time (as I am just using a pot on a hob). Plus, I wondered if having the grain wadded up a bag makes it harder to get the optimum out.

I understand I can troubleshoot by adding DME if SG is low.

Or should I add more grain at start to compensate for some inefficiency in my set up?

How would others seek to unsure I get those good malty sugars out the grain?

Any pointers most appreciated.

Cheers,

Ross

 

[myndflyte]

I'd look at the crush of your grain. Did you crush it or was it crushed by the homebrew store? With BIAB, you can double crush it on the tightest setting and be fine. You'll see your efficiency go way up.

 

[Rosshedley]

It was crushed when I brought it, but maybe not enough I guess.

Thanks.

 

[myndflyte]

The only other thing I can think of is that the bag or pot you're using is too small. Also, there are some errors with what the recipe is saying. Your pre-boil gravity should not be 1.065 if the original gravity is supposed to be 1.050. So if you collected 2 gallons or so from your mash, it should be around 1.033 so you're not that far off.

Was your pre-boil gravity 1.023? And if so, what was the gravity of it when you put it into the fermentor?

 

[Rosshedley]

Oh yes had not noticed that 1.050 / 1.065 discrepancy before.

Pre-boil gravity was 1.023. When in fermentor it was 1.024. (I had just under 1.3 gallons, but volume does not matter when measuring gravity, right?)

 

[myndflyte]

Oh yes had not noticed that 1.050 / 1.065 discrepancy before.

Pre-boil gravity was 1.023. When in fermentor it was 1.024. (I had just under 1.3 gallons, but volume does not matter when measuring gravity, right?)

Well it does matter to an extent because if your pre-boil gravity was 1.023 and your post boil only increased to 1.024, either you barely got any boil off or your pre-boil measurement is off. Because if you're boiling from 2 gallons down to 1.3, you gravity should increase by more than 0.001.

Regardless, the gravity that means the most in this case is the one from the fermentor. Everyone's first AG is like that because its a new process. If you can, get the grain crushed twice next time and it should help a bit.

 

[JimRausch]

Did you add any top-off water when you put the wort in the fermenter? It doesn't look like you did, but it's not clear. If you did it might be a stratification thing and your OG maybe closer to what you wanted.
If no topoff and your volume was correct, then an incomplete crush as myndflyte mentioned above is the most likely culprit. Another thing to consider is that adding heat by turning on your burner several times over the course of the mash, may have led to hot spots in the kettle which could denature the enzymes. Enough to mess up your OG? Possible.

 

[myndflyte]

Oh yeah I forgot about hot spots. One thing you can do to help control the temp is set your oven on the lowest setting and put the pot in there after you mash in.

 

[Rosshedley]

Cheer people! All very helpful.

No top-off added. Will get grain double crushed next time, as well as ensuring I have some DME in just in case I have same problem.

Will try oven tip too.

Ta,

Ross