BIAB sg low???

Mr BR · Dec 3, 2012

hi did a brew today with 3kg of lager malt, 3kg pale malt, mashed at 66 degrees for 60 mins, boiled for 60min ,took the sg 1034 ,does this sound about right as i was thinking it was a bit low ,did the recipe on brew smith and i think i have cocked it up somehow but cant think how, any help appreciated,thanks

StevieDS · Dec 3, 2012

Im fairly new to AG myself but that is def a bit low. You should have had around 1.060 with a 22.5 litre batch at those quantities. If you've got 1.034 that means you have a mash efficiency of less than 50% which is very low. Can't think why, if your mash temp was good :wha:

Duncs · Dec 3, 2012

60 minute mash seems a little short. I thought 90 minutes was the minimum time. When I brew biab I mash fir 150 mins

StevieDS · Dec 3, 2012

150 mins really? Ive only done 1 biab but I only mashed for 60 mins and I used less grain than this and it give me og of 1.052. I'll maybe try 90 mins next time but I still think 1.034 is very low even for a 60 min mash.

mmaguy41 · Dec 3, 2012

Did you sparge the bag? I do biab with a 19l pan atm and i have to sparge the bag around 3 or 4 times with a ketlle of hot water to get near my taget

bunkerbrewer · Dec 4, 2012

I'm fairly new to AG myself, but how much do you trust your thermometer? I had problems with my first two BIAB brews caused by a thermometer that was about 3 degrees out (high final gravity in my case).

TheMumbler · Dec 4, 2012

What was brewlength and your predicted OG?
Does BIAB have horrible efficiency? I've never tried it.

Assuming a 23l brewlength 1034 is very low, I would guess at an expected OG in the region of 1060 for 6kg base malt and a 23l (5 UK gallon) brewlength. I normally mash for 90 mins but I really don't think that a 60 min mash would explain that kind of drop in efficiency.

I think your most likely cause is some sort of measurement error. Sorry if this list is a bit basic but it is a good idea to try and rule out silly mistakes :)

Did you account for the temperature of the wort when you took the reading?

Are you sure you put 6kg of grain in? Your OG looks like there should have been around 3kg...
Have you checked your hydrometer? Does it read 1000 in water at the temperature it is calibrated for (normally 15 or 20 degrees celsius)
Does your thermometer read 100 in boilng water (although tbh it would have to be miles out to cause that sort of difference so I think we can probably rule that out as a primary cause)

calumscott · Dec 4, 2012

That does seem low to me.

My brew at the weekend was:

5kg M.O.
37l water.
75mins @ 66-67C
heat to 77C (over around 15mins)
10 mins @ 77C

and it came out at 1.039 pre-boil which gave me 20.5l @ 1.048 post-boil.

Mr BR · Dec 4, 2012

thanks all for the replies ,checked everything twice and adjusted for temp on hydrometer,all i can think of is that the mash was not long enough and would need 120-150 mins to mash as the grain bill is 6kg : cheers:

calumscott · Dec 4, 2012

How much liquor went in with the 6kg?

Mr BR · Dec 4, 2012

30ltr just what beersmith said for a 23ltr finished brew length,first time i have used beersmith so dont know if it any good

calumscott · Dec 4, 2012

Yeah, I use beersmith too. Seems pretty comprehensive to me.

No idea what's gone wrong there then. How were your temperatures?

Mr BR · Dec 4, 2012

have just taken an other sample and put the hydrometer in at room temp and its reading 1040 now so the temp must have been out but still not what i expected,have just pitched yeast and am starting the fermentation /lagering process,so into the temp controlled fridge it goes.

calumscott · Dec 4, 2012

Did your mash temperature stay nice throughout the mash?

Mr BR · Dec 4, 2012

kept a close eye on it ranged between 64-67 using one element to top up when heat dropped to low ,still think it just wasnt mashed for long enough.

calumscott · Dec 4, 2012

Yup, I can't think of anything else then... Chalk it up as just one of those things I reckon...

...unless it happens again of course!

Mr BR · Dec 4, 2012

yeah a think its one to the learning curve,will mash for longer next time,hopefully this cures it.

fbsf · Dec 5, 2012

I tend to overnight mash, just with a well insulated mashtun (lots of blankets and duvets) - this normally does the trick for me, but also means I can start it off late on an evening, go to bed, and have a shorter brewing day the next day...

puravida · Dec 5, 2012

Doughballs perhaps???
Hard to avoid clumping with that amount of grain.

calumscott · Dec 5, 2012

puravida said:
Doughballs perhaps???
Hard to avoid clumping with that amount of grain.

Ah, yes, missed that possibility...

BIAB sg low???

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