What is the max sparge volume/ratio to avoid over sparging a low OG bitter?

[TAK]

What is the max that you would sparge a small grain bill?

I know that "over sparging" will pull out tannins and acridness from the grain. So, for a small grain bill like you'd have for an ordinary bitter, I expect that I won't get all of my water from mash and sparge. I'll need to top off with some additional water before the boil (of course you could post boil also) in order to get my full volume.

Example: With my equipment, for a 60 minute boil, I always aim for about 6.67 gal pre-boil which gets me to about 5.33 gal post-boil, and I batch sparge. If I have 7 lbs of grain and mash at 1.25 qt/lb, that's 8.75 qts. I usually top off before collecting my 1st runnings with whatever amount will equalize my 1st and 2nd running volumes. So, I might top off with 3.5 qts, which brings the thickness to about 1.75 qt/lb, and then pull my 1st runnings. With my equipment, I'd expect to get 1.93 gal from the 1st runnings. Then 7.75 qts of sparge would give me an equal volume for my 2nd runnings. Thus, the total volume from the mash and sparge is about 3.86 gal. So, I'd top off with about another 3 gallons prior to the boil.

I know everyone's equipment is different, but does this sound about right? How far can you push the volumes of the mash, top-off, and sparge without getting too thin and pulling tannins? I don't want to push it too far, but I also want to be sure I sparge enough to get my expected extract.

 

[Yooper]

The easy answer is to use a hydrometer or refractometer and stop pulling runnings when you hit 1.010. Or, use a pH meter and as long as the runnings are under a pH of 6, tannin extraction is not going to happen.

If those tools aren't available, a guestimate that I've read is to allow no more than 3 quarts of water go through each pound of grain, including the mash and sparge, and that would avoid possibilities of tannin extraction.

 

[TAK]

...use a hydrometer or refractometer and stop pulling runnings when you hit 1.010.

Just to clarify, do you mean when the runnings themselves hit 1.010? In other words, that is not the aggregate pre-boil runnings, but the runnings right out of the mash tun that start high and drop as you run through the sparge?

I suppose this only works for continuous sparging. I've always batch sparged, but that commits one to the sparge volume. I havn't taken readings of my runnings as they go, but I expect that in a batch sparge situation, since it's all in solution, the gravity is uniform during the sparge. I don't have a sparge arm, but I imagine that I could manually sparge a quart at a time until I hit the mark with my refractometer.

 

[AT-JeffT]

Just to clarify, do you mean when the runnings themselves hit 1.010? In other words, that is not the aggregate pre-boil runnings, but the runnings right out of the mash tun that start high and drop as you run through the sparge?

Yes, the runnings from the mash tun.

I suppose this only works for continuous sparging. I've always batch sparged, but that commits one to the sparge volume. I havn't taken readings of my runnings as they go, but I expect that in a batch sparge situation, since it's all in solution, the gravity is uniform during the sparge. I don't have a sparge arm, but I imagine that I could manually sparge a quart at a time until I hit the mark with my refractometer.

You are correct, this works better with continuous (fly) sparging. If batch sparging you could check the gravity of the runnings (by running a bit into a separate container) and then discard the runnings if too low.

 

[Ortega917]

I wouldn't go lower than 1.010 I always check each runnings with my refractometer but I never get that low anyways I usually have my preboil volume before hitting 1.010... Cheers!

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