High SG

[gusty]

G,day Brewers I'm new to BIAB and have only done 3 batches witch have turned out really nice!, every batch I've done have had a very high SG after a 60min boil, I have been using rain water to top up water level lowering the SG..., Am I doing something wrong? Or am I losing to much through boil?? Any advice would be appreciated!.

 

[wereprawn]

Hard to say. What volume were you expecting? What was your grain bill? What is your boil off rate?

This might give some insight into the subject. http://braukaiser.com/wiki/index.php?title=Troubleshooting_Brewhouse_Efficiency

 

[manticle]

More details on recipe, process and expected vs actual numbers please.

 

[Screwtop]

On Oldie But A Goodie.................................. What are you using to measuring the gravity and what was the temp of wort at the time.

Screwy

 

[gusty]

My grain bill was
4.2Kg Heidelberg malt
1Kg flaked corn
.2kg crystal malt
Mash in 72c
Mash out 93c
Expected SG 1047
Pre boil vol 24L

Post boil I got 1060 @ 23c but only got around 15L with 2L of turb left..., I used a stainless kettle as my mash in and an esky as my mash out.

 

[wereprawn]

Sounds like you are getting more boil off than expected. Try adding an extra 8 ltrs next time.
Or if your boiling unit is not big enough ( mine is a 30 ltr urn so i do this) heat another pot on the stove or boil a few kettles worth and add a few minutes before the end of the boil to make up the difference.
The height and width of your boiler will make a difference.
Or just top up with tap water to desired volume/gravity.

 

[manticle]

Mash in strike water 72 or actual mash? Mash out water 93 or actual mash?

Very simply if your numbers aren't what software tells you, adjust the input till it reflects what your system actually does, then adjust the recipe until it hits the numbers you want. Maybe your mash efficiency is set too high.
As wereprawn points out though - if gravity is high but volume is low, you are likely losing more to evaporation than expected. Again, calculate what you lose in reality then plug those numbers into software and adjust the recipe. Software is for guidance - it's not a wizard. You need to give it the basic info so it can offer reasonable predicted outcomes.

 

[Blind Dog]

Nothing to add to the above re SG (although your mash temps seem high) but I would be concerned using rain water to top up unless that had also been boiled. Might just be that my rainwater tank is a manky thing, yours may be fine

 

[gusty]

I'm using a converted 50L stainless keg, with a triple ring burner, I'm thinking I'm losing water there?, the temps are strike temps sorry mash in is 65c and mash out is 75, but my mash out temp was a little high around 77-78c
I might cut a burner out once I get a rolling boil happening,
The rain water I'm getting is out of a new tank so should be right with that.

 

[manticle]

77-78 is actually perfect for mash out.

Do a run with just water and calculate your boiloff rate. Factor in liquor/grain losses and trub losses and use those figures.

 

[gusty]

Oh ok well that's good, yeah I'm still learning and getting a hang of it,
So if I'm getting a large boil off rate would I bump up my mash in and mash out water by a couple of litres each?
What software or charts do you use to work it out?, as my set up is real basic....

 

[manticle]

Calculate your losses to grain absorption and tun loss then add enough liquor at the right temp to get the preboil you need to result in the post boil you want (incorporating trub loss as well)

So for hypothetical example - Let's say you lose roughly 1 litre per kg of grain + 2 litres that remains in the bottom of the tun.

You lose 10 litres in an hour to boiloff.
You lose 3 litres to trub.

You want 21 litres in your fermenter.

This means you want 34 litres preboil.

You have 6 kg of grain so you lose 6 litres + another 2

34 + 8 = 42 so you need to run 42 Litres of water through your mash. It depends on your setup and process as to how you do this. I run an esky mash tun so with these numbers I would mash in with around 15 Litres of water, mash out with 8-10 Litres and sparge with a further 17-20 litres.

If BIAB, no sparge you'd just mash in with the lot.

 

[TimT]

You lose 10 litres in an hour to boiloff.

Is that true? I'd say I lose less than half that.

Possibly because I adjust the temp once it hits the boil to make sure it doesn't just climb out of the pot.

 

[manticle]

Hypothetical as mentioned but I do lose close to that. Actual figures will differ system to system.

The principles are important, not the figures offered.