Low gravity reading

[Hawko100]

I was aiming for a post boil reading of 1044
But checked my wort this morning after boiling last night and putting in the fermenter, and my Gravity was at 1020.
Used 5kg of grain
Grains where cracked fine.
Mashed for 60 minutes at 62 degrees.
Sparged in a 19 litre pot in 8 litres of water
Boiled for an hour
Dropped temp to 60 degrees then transferred to fermenter.
And let rest over night to drop temp.
Checked this morning before pitching yeast
And was at 1020.
I did the exact same beer 2 weeks ago and hit my target.
Any suggestions?

 

[gap]

How much water did you use for the mash?
I assume you did not take a preboil gravity reading , you should
What was your preboil volume?
What was your post boil volume?

 

[Hawko100]

15 litres mash
Pre boil was 28 litres
24 litres post 22 in a fermenter

 

[gap]

62 is very low to be mashing at, also are you sure your thermometer is accurate?
also did you do an iodine test for total mash conversion?

 

[Hawko100]

No I don't have an iodine test.

 

[Hawko100]

Between the urn settings and the thermometer I don't think I'm far out.

 

[Rocker1986]

60 minutes isn't really long enough for a mash at that temp either, you want at least 90 minutes, or so I'm led to believe anyway. This may be playing a part.

 

[Hawko100]

I'll give that a go next time, but this time I'm going to have an extremely light pale ale

 

[gap]

It could also be full of starch because of incomplete sugar conversion.

 

[manticle]

Firstly, I reckon you've got faulty equipment which could be either thermometer or hydrometer.

Secondly, if mashing really low, you are favouring beta amylase - allowing alpha some scope as well will increase your extraction efficiency.

If mashing low, you can increase the rest period as suggested by Rocker although I'd be surprised for a 60 minute mash at 62 to result in that gravity, all else being equal.
If thermometer is even 1-2 degrees out and the temp dropped another 1-2 degrees during mashing though, that would contribute.

 

[Hawko100]

I'll mash the next a bit higher.
I'm going to test my grain cracking as well, as I'm going to get the local hb shop to crack my grain ( never had this drama when he did it) and then I'm going to do the exact same brew the next day cracking my own, I'm going to buy this thing out cause I don't like drinking lights.

 

[Jack of all biers]

I agree with Manticle, it's likely a faulty thermometer. I had that once (when I re-calibrated my thermometer I found it was reading 6C higher than actual temp) and it sucks. Calibrate your thermometer against a couple of others to see if it's out. To check your hydrometer, test it in water and it should read 0 then test it in a known quantity, make up a 1040 amount with dried malt extract and test it again. I doubt also that it was your crush, as you would have noticed a large amount of uncrushed grains otherwise.

60 min mash time is fine for just about any grain at 62C, but what grains did you use.