BIAB Mash. How thin is too thin?

Brewing Processes
1

I want to brew a 6 gallon (in the fermenter) batch of an English Mild recipe that I have designed.  Pre-boil volume should be about 7.5 gallons so that would mean about 8 gal. in the kettle for the mash if I do a full volume BIAB mash.

Two additional complications:

  • 14% of the grain bill is a lb. of Crisp Crystal 77 that I want to add at the end of the mash.
  • 17% of the fermentables is 20 oz. of invert sugar syrup #2 to be added at the end of the boil.

That leaves only 5 lbs. of grain in the mash which means the grain to water ratio will be a whopping 6.4 qts/lb.

Will that be a problem and why?  Thoughts and suggestions greatly appreciated.

2

My BIAB batches usually come in between 3 and 4 Qt./gal. so not real sure what level would be out of line. You need to be a lot more aware of your water as the ratios get higher to be sure you have enough calcium and that the pH is within limits. If you want to play it safe you could always use less water in the mash and either sparge and/or top off your kettle to the desired volume.

3

I do full no-sparges on ALL of my beers and I rarely go over 3 qts/# W/G ratio. Your main issue with going over that amount is you are not only thinning out the mash but also thinning out your enzymes which can make them work more slowly simply because they are now floating around in more water rather than working on conversion. This can affect your overall efficiency and therefore your OG.

I like Bob’s idea with mashing at a more normal ratio for your saccharification rest and then maybe add your additional water to hit a mash-out temp of 170F or so. At that point, your conversion will be complete with a normal W/G ratio and adding your additional water will bring up your mash temps prior to running off into the kettle. Just be aware that you don’t go too much higher than low 170’sF which could lead to extracting too many tannins leading to astringency especially if your pH gets too high.

4

That makes a lot of sense.  I’ll try a 4 gal. mash with all minerals in the mash water and then fly sparge/top up with 4 gal. of 168F RO water.  (Yes, I can fly sparge BIAB)

5

I pay no attention to grain to water ratio when doing full volume BIAB. All I am concerned with is ending up with the required volume out of the boil kettle.

6

So since maximum gravity lowers as wtg gets higher (something like 100% conversion at 3qts/lb is like 1.044), how do you make beers above say, 1.055? Just boil off a lot?