I don't work at Mini-BIAB scales, so am not sure, but you do get a fair bit of evaporation. Anyway, you add as much of your sparge back during your 90 minute boil (this gets you more evaporation) as you can. Its best to make sure you don't add sparge during the last 10-15 minutes so that your final addition has time to sterilise.truman42 wrote:Hello Im new to BIAB and want to give it a try but have a couple of questions. If I start with a 19 litre pot and pull my bag out to Sparge and end up with say 15 litres in my pot. Then I sparge with four litres and pour more water over the top of the open grain bag and stir for 15 mins then pull the grain bag out and pour this in the pot which might be say 3-4 litres which takes my pot volume up to 18-19 litres. If I do a second sparge as per the instructions I wont have any room for this liquid to go into the pot as well? I know you can put it aside and add it later but surely it wont reduce that much that I can add the extra 2-3 litres?stux wrote: The big trick is not to over-sparge and end up with more liquid that you can fit in your pot, or boil off

If you can't add it back, then don't worry about it.

Pitching temperature is normally about 20C or so. You should be able to feel the outside of your pot with your hand... once its cooled some. If its cool to touch, or at room temperature, then that's good enough.Also I am having trouble with this part here and want to make sure Ive got it right.

Ok, so our stockpot has cooled to pitching.

How do we know when it has cooled to pitching if we cant open the lid to check it with a thermometer?

Or you can put a sanitized thermometer in. If you have to take the lid off, then so be it.

I personally take a sample of wort at the end of the boil, while its still boiling hot. I let that cool separately and measure the gravity of that sample, and give it a taste. Then I can work out my dilution once I pour it into my fermenter... which is graduated (i very carefully measured out and drew the markings on it myself once upon a time, and have since copied them to three other fermenters )We need to know the Specific Gravity and Volume of the wort (estimate the volume if need be- the kettle is usually full almost to the brim at the boil end, but shrinkage due to cooling will mean that there's a lower volume at pitching). We want the cooled volume, but don't under any circumstances open the lid or touch the wort until you are ready to pitch, even then anything that contacts the wort must be scrupulously sanitised.

How do we get the post boil SG if we cant open the lid?

The other way I do it is to no-chill in an HDPE cube, and then i fill my fermenter from that. I can then run some wort through the tap for a gravity sample.

Well, if you wanted 1.060 instead of 1.046Work out the dilution, this formula is usually good enough:

Post- boil Specific Gravity / Target Specific Gravity * Post- Boil Concentration = Diluted Volume

So if my post boil SG is 1.070 and my target OG is 1.046 the formula would be 70/60*18=21.06-18=3 litres (assuming my 19L pot has reduced to 18 litres) So I would just add 3.06 litres of water into my fermenter? Shouldnt I also allow a bit extra for trub left behind in the pot?So make my post boil volume 1 litre less??

But if you want 1.046 then it would be

60/46 * 18 = 27.4L, -18 = 9.4L

The correct formula is actually

(SG1-1)/(SG2-1) * V1 = V2

Thanks for the help.