Low OG - suggestions why?

[chrisluki]

Proving to be a very steep learning curve this AGB caper!

Just looking for some suggestions as to what I need to investigate to get to the bottom of this?

Target OG was meant to be 1.04 or so and I got a reading of 1.02. Could it be mash rest time, or the way I have milled my grains, or perhaps my sparging?

Any suggestions welcomed

Cheers

Chris

 

[MHB]

In short YES it could be any of the things mentioned and a couple of others.
If you want a useful answer to the problem you will need to provide a lot more information on what went in and how you used it.
Mark

 

[wereprawn]

Could be any number of things. You will need to post a detailed description of your method and ingredients .

 

[pat86]

What temp was the wort when you took the reading and how did you take the reading? I use a hydrometer and if the wort is >20C use one of the hydrometer temp correction calculators - free just Google it or find an app.

If you are using a refractometer, do a search here as lot of people have issues the first few times.

Seems to be a big gap so if it wasn't reading error then must be something significant, would look at milling and your set up.

For this one you can always just boost it up with DME though as a partial, easy!

 

[chrisluki]

Thanks guys...

Recipe steps...
3.2kg of Pale Malt
0.9kg of Amber 60EBC
0.227kg of Crystal 120EBC
0.113kg of Choc Malt

Milled with a standard Keg King 2 roller mill set to the middle setting. Looked like I had a nice lot of husks and could see the white innerds as well.

20l Strike water as I had to add in 1.5litres to get up to my mash temp of 67 degrees.

Mash rest for 60 min, stirring every 20 minutes. Finals temp was still 63.7.

Ran off a couple of litres, came out clear, poured back over mash then ran all into the kettle very slowly via a hose.

Added 11.5 litres back onto the mash and left it for 15 minutes. Ran it into the kettle and put it into boil. Took a sample in my test tube thing and it was mid 60's when I put the hydrometer in and got 1.021 against a target of 1.041.

I dropped and smashed the hydrometer after this, so no final gravity reading. Think my refractomoter should arrive tomorrow, so I will check the fermenting wort with that.

Boiled for 60 minutes, it was probably closer to 95-97 degrees most of the time but bubbling away. Hops at start and finish and then cooled down with my immersion chiller.

Transferred to my primary fermenter and pitched the yeast I had rehydrated earlier. Left for a few hours and noticed a small puddle around the bottom of the fermenter...damn bung was not quite screwed in enough! Didn't look like fermentation had started, did up bun and placed a warm blanket around fermenter for overnight. Getting a heat belt this week.

Overnight temp was about 20 degrees, didn't open the vessel this morning (too scared I would ruin it!) buy it looked like a ring of foam was starting to form around the edge...no bubbles in airlock as yet.

Starting to realise that it's a huge jump into AGB with 3 vessel keg kit that I made myself....so much to learn about theories but using a brand new untested kit also has it's challenges.

It hasn't broken me, I am keen for more.

 

[wereprawn]

Taking a hydro sample in the mid 60's is your problem. Have a squiz at this.http://www.brewersfriend.com/hydrometer-temp/

 

[MHB]

If as I gather from your post you took the SG at ~65oC then your OG would have been about 1.037, mind you if it was closer to 70 then it would have been pretty close to 1.040.

You haven't said how much you got to the fermenter, working on what you have said; total water in (20+1.5+11.5) = 33L, lets say you left 0.8L of water per Kg of grist in the mash; Kg Grain less loss (4.44 X 0.8) = 3.552 L; so to the kettle we are looking at about 29.5 L; say your boil off was 10% leaving 26.5 at the end of the boil.

This is very back of the envelope and not much more than finger counting really; 4.44 Kg with a total potential of about 77% gives a potential yield of 3.4188 Kg of extract.
3.4188Kg in 29.5 is 11.6oP or about 1.046 at 100% efficiency; if your brewhouse efficiency was 80% the OG would be 1.037.

So all things considered, for a cherry popper on a new system it looks to me like you haven't done too badly.
Big take home lesson is to cool your sample to what the hydrometer is calibrated to (it should be written on the hydro) and don't break them halfway through the brew day.

Good luck with the brewing and buy two hydrometers a spare is always handy
Mark

PS
Don't get a heat belt, 20 is a good fermentation temperature, if your over night is 20oC, and summer is coming, think more about how to cool your ferment, not heat it up, for Ale 16-20 is the nuts, hotter and the beer will start to suffer.
M

 

[manticle]

You took hydro sample before or after boiling?
From my reading, you ran off into the kettle and took a sample as it was heating up. Boiling will reduce volume and concentrate the sugar content, thus increasing the gravity.
As mentioned, sample will read lower when hot.
To head you off at the pass now, read up about correcting for the presence of alcohol when using a refractometer- something you will need to do when you sample your fermenting wort.

Once we know 1020 was definitely the final reading we can make suggestions. What mash efficiency did you set to get 1.040 expected sg and what was the intended and actual final volume?

 

[chrisluki]

Huge thanks to you all for this...what an awesome community this place is.

Sounds like all may not be lost, but much to learn for me.

Taken on board all of your comments and suggestions...I need to read up a bit on the maths of it all I think.

Here's hoping those little yeasties start to get munching on that wort and I get something resembling a beer in the coming weeks!

 

[chrisluki]

Sample before boiling by the way

 

[manticle]

And was 1040 calc also meant to be preboil (I'd be surprised with that grist) or post-boil?

 

[chrisluki]

Got some nice fermentation going as of yesterday arvo, happy with that!

Turned up at work today and my refractometer has arrived too!

 

[nolube]

Hey guys, fairly new here so I hope I've picked the right thread. :beerbang:

Brewed an IPA the other day..

4.5kg Marris Otter
500g Wheat
500g Carmunich 1
500g Carmunich 2
500g Munich

Mashed at 69 degrees for about 45 minutes (tested with iodine and conversion was complete)..

OG should have been 1.085 but came in at 1.061..

Haven't had one come in that far off for a long long time and only thing I can think of was the Marris Otter was probably just over a year old. Only other thing was maybe the strike water was too hot and killed the enzymes as it would have been 73 or 74 when it touched the grain.

Does one of those reasons stack up more than the other? Or is there something else I should be considering??

Cheers

 

[manticle]

What size batch?
There'll be other questions like the ones above about your processes and equipment.

 

[nolube]

20L batch.. I brew very frequently and have never been this far off and the process hasn't changed. So I'm thinking it has to be

a) the old Maris Otter
b) higher mash temp has killed the enzymes (but why then did the iodine test read negative? Or would it make sense that read negative??)
c) something else I haven't thought of..

 

[chrisluki]

Thanks for your thoughts guys!

 

[manticle]

20L batch.. I brew very frequently and have never been this far off and the process hasn't changed. So I'm thinking it has to be

a) the old Maris Otter
b) higher mash temp has killed the enzymes (but why then did the iodine test read negative? Or would it make sense that read negative??)
c) something else I haven't thought of..

You're a better man than I if you can get 20 L of 1.081 out of 5ish kg of base malt.

 

[nolube]

I use the recipe calculator at brewersfriend.com and I've only ever been a few points off...

 

[Blind Dog]

You're a better man than I if you can get 20 L of 1.081 out of 5ish kg of base malt.

And still a better man if it's 6.5kg (being a pedant, or is that peasant?)

Very rough rule of thumb I use to double check recipes is 1kg grain (22l batches) gives 10 points of gravity for up to 5kg or so and then drops fairly rapidly. And yes I know it's very rough and is affected by loads of variables, but it's only a sense check. So sIngle mash of 6.5kg on my system should get me an OG of around 1.065

 

[Blind Dog]

What efficiency do you use in the calc and what were the grain bill and batch sizes for the recent brews you were only a few points off?

Different systems have different limits but I've yet to har of a system where efficiency is not fairly drastically affected as that limit is approached