BIAB Partial Mash

So I've read Deathbrewer's sticky where he dunk sparges his grain bag in a separate pot of 170 degree water. I've also heard of people using thin mashes equal to the full boil volume and doing no sparge.

My question is whether a hybrid method would be successful for a partial mash and not lower my efficiency too much. I don't like the idea of a full volume, no sparge, thin mash because if you're boiling 6.5 gallons and only mashing 4 lbs that's a water to grist ratio of 6.5 - too thin! I'd probably have to mash for like 2 hours to get good efficiency. So could I mash 2 gallons for 4 lbs (grist ratio of 2) for 60 minutes, drain the grain bag, top up to 6.5 gallons, add the extract, and boil?

I guess I'm really just wondering whether using a thicker mash would offset lower efficiency by skipping the dunk sparge.

BPal75 said:

My question is whether a hybrid method would be successful for a partial mash and not lower my efficiency too much. I don't like the idea of a full volume, no sparge, thin mash because if you're boiling 6.5 gallons and only mashing 4 lbs that's a water to grist ratio of 6.5 - too thin! I'd probably have to mash for like 2 hours to get good efficiency. So could I mash 2 gallons for 4 lbs (grist ratio of 2) for 60 minutes, drain the grain bag, top up to 6.5 gallons, add the extract, and boil?

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When I do partial mashes, this is the method I use. I never had success with full-volume mashes either.

You could even mash in 2 gal for an hour, then top up with water, and then remove the grain bag. That way you'd still be mashing in a low enough volume where you ratio isn't too high, but you get a little bit of a sparge component since whatever water is left in the grain after you remove it is of a lower gravity. I guess it depends on how well you're able to drain your grain bag as to whether you'd see an improvement or not. Obviously the temps are going to be pretty low since the top-off water probably won't be heated, but at that point it would mostly be about rinsing the grains. I've also heard of people pouring the top-off water over the grain bag, but that assumes you've got something to hold the grain bag up above the pot, which might not be available.

Another thing to consider would be potential tannin extractions due to the lower temps and any water effects you've got, and having not tried this, I can't help you with that part. Maybe someone else can though!

I use the dunk sparge method because it works well with my equipment and gets me better efficiency. I mash up to 6lbs of grain in a small 3gal pot at a 1.25-1.5qt/lb ratio, this is small enough to fit in my oven preheated to warm. Then I put the sparge water in my 10 gal kettle and dunk sparge in that, then add the first runnings and bring to a boil.

For doing it all in the same pot...I'd do what you are suggesting. Or...try it both ways; full volume and partial volume for a 60 minute mash and see if it really does effect efficiency? If efficiency is the same, the full volume mash is easiest.

Thanks for everyone's opinions, that's helpful. I'd never heard about tannin extraction at low water temps, I'd always thought that was only a concern above 170. Something to consider.

BPal75 said:

Thanks for everyone's opinions, that's helpful. I'd never heard about tannin extraction at low water temps, I'd always thought that was only a concern above 170. Something to consider.

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Oh yeah, I've never heard anything about tanning extraction at lower temps either, just didn't want you making a tannic mess and blaming me . The only reason I could see it being a problem is that I think the pH goes up as the temp decreases, but I've got no idea if that would actually extract tannins or not.