Can someone help me get my head around this?

[sbond10]

The norm for ag is heat water- mash- sparge -boil
where as full boil volume biab is
heat water-mash-boil

So I know sparging shakes lose the sugar prior to boiling. So how does this happen in biab.
I've been playing with a biab calculator and for a 23 litre batch ( leaving everything set to norm values )
ill need 40 litres of water once grains in pushing up to 46 mark.
So my only theory is the incredibly thin mash allows the sugars to come off easier.
This was for a mild of around 1.038 the calculator also reckoned i should have a pre boil gravity of 1.050 does this sound about right.
I know the calculator would need fine tuning to my personal equipment. But it's mainly the sugars that are worrying me.

[Grumpydev]

There's 1001 ways to BIAB, some will lift the bag out onto a colander on the top of the boiler and sparge it, others remove the bag then increase the water temperature and put the bag back in for 15mins or so, some just squeeze the hell out of the bag when they lift it, and some don't do any of these things and just compensate for the lower efficiency with more malt.

[AnthonyUK]

Wait for the inevitable sparge/no sparge 'discussion'.
I'm in the no sparge camp as I feel I get a good enough efficiency at 70% and the time saving and extra hassle is not worth a few measly % points gain in efficiency.
The efficiency can easily be counteracted by using slightly more grain e.g. max 50p cost increase and there are benefits to not overextracting.

For a 23l batch I start with approx. 35l. If you want to try a sparge to see if it makes a difference to you just remove 5-10l once it has reached strike temp to a larhe pot and close to the end of the mash heat it up to 80°c.

If the mild was 1.038 how did yoy end up with a pre-boil gravity of 1.050? Your post boil would be even higher.
Were you diluting post boil?

The most compelling reason for not sparging comes from Pat Hollindale who was one of the pioneers of BIAB which you can hear talking in this podcast about it -

http://traffic.libsyn.com/basicbrewing/ ... legacy.mp3

[vacant]

The mash dissolves sugars rather than shaking them.

BIAB and batch sparging are the same principle as a brewing tea. Once brewed you drain the pot to get your strong tea out (first sparge) but because the leaves are saturated, you don't extract all the tea solution. Filling the pot again, brewing on those leaves and draining will give you another lot of weaker tea (second sparge). BIAB is the same as a teabag but using a pot with twice the water.

However, BIAB (or dumping all your water in and just doing a single sparge) is 9% less efficient that a traditional two stage sparge. I did some theoretical calculations here. I assumed the % sugar solution trapped in the wet grain was the same as the wort.

Fly sparging is more efficient still as it gradually flushes the wort solution.

[sbond10]

No I wasn't post diluting I just noticed a bit that said pre boil gravity. I'm going to use a 70 litre pot so no need to post top up. Is there a way of knowing ypur pre boil gravity will meet your post boil gravity?

I noticed the biab calculator adjusted the grain amounts so I'm guessing this has already taken into account I'm not sparging. I reckon for my first time round if I set the efficency at 65% then I can tweak it after my first brew and hopefully after 3 brews I should have more numbers

I'm thinking sparging may only be really need for high abv brews where efficency is key ?

[sbond10]

Having a thought put it all thru the calculator mash minus 5 litres. When Mash is done lift bag out of water and drain five litres off and pour this over the grains and then same again with the other 5 litres witch would be heated to around 85 c. Would this work or am I likely just confuse my self for first brew

[rpt]

Get the BIABacus and let it work out everything for you. Don't bother sparging. Make it simple for your first brew.

[sbond10]

that's the calculator I'm using or one from biab forum

[rpt]

If you are using the BIABacus then don't set the efficiency, let it estimate it for you. If you decide you need to adjust it then do it by setting the "Adjust auto kettle efficiency by" field. I have set this to 5% as I found I was getting slightly higher gravities than it estimated. You don't want to set the efficiency to a fixed value (such as 65%) because the efficiency will naturally vary - higher gravity brews are less efficient.

[sbond10]

So leave standard settings alone do first brew then start playing. It's doing my head in which calculator I have I know it's off the biab forum but I'm on my phone so couldn't tell you