When to stop the fly sparge?

[hal simmons]

I fly sparge and have been getting good efficiency using this method. I know you're supposed to stop sparging once the runnings are below 1.010. When I get close to the end of the sparge I typically check the runnings frequently to make sure i'm not below this mark.

My question is that once my runnings out of the bottom of my MLT are below that number, but I need a little bit more volume in my kettle, is it OK to just stop the sparge water that is flowing in, but keep draining out whatever liquid is still in the MLT? My thinking is that if I need a little extra volume pre-boil, the water in the MLT is still going to have some sugars in it VS top up water which doesn't. But...I don't want to extract any weird flavors or anything from the grain if this is considered over-sparging.

 

[maltMonkey]

You definitely don't want to use anything below 1.010 or 1.008 out of the MLT, regardless of if you're still circulating water or not.

Are you sure that you're ever actually getting that low (you are correcting for temperature, right)? When I measure my final runnings I'm usually still in the 1.025 range after collecting 7 gallons.

 

[Yuri_Rage]

The easy answer to your question is: "When you're done!"

If the runnings get really thin, it's time to stop. If you have collected your desired volume, at the desired strength, it's time to stop. If you need more volume, and the runnings still contain sugar, keep going.

As you've found, you wind up with several gallons of excess if you keep adding sparge water until the boil kettle is full. You don't have to do that. You can stop adding sparge water and completely drain the MLT. That's often how I finish up mine. For a 15 gallon batch, I dough in with 10-12 gallons, then sparge with another 10-12 gallons to get 17.5 gallons to the kettle. The MLT is usually nearly dry when I'm done.

 

[Boerderij_Kabouter]

If your runnings are below 1.010 you will be extracting tannins that will add astringency to your beer. Even if you stop adding sparge water, your running will continue to drop in gravity as you drain your MLT. You can think of fly sparging like sheets of water flowing through the grains. Each sheet has less and less sugar absorbed as it passes through the grains. If you are not reaching your target volume a gravity, try testing you efficiency to get a better grasp on where you stand. If your efficiency is low (60%) you will likely need to up your grain bill to accommodate. You can search efficiency and you will find a number of good threads, or check out the chapter in Palmer's "How to Brew".

Hope this helps.

 

[hal simmons]

Are you sure that you're ever actually getting that low (you are correcting for temperature, right)? When I measure my final runnings I'm usually still in the 1.025 range after collecting 7 gallons.

Yeah my first batch I calculated for 65% efficiency and ended up getting 85% so I left sugars in the MLT. This last batch I had calculated for 85%, so my last gallon of runnings was around 1.010 (adjusted for temp)

 

[maltMonkey]

hmmmm.....how much wort are you collecting and what is your final batch size? I guess if you were collecting enough for a 2 hour boil I could see this happening.

 

[hal simmons]

hmmmm.....how much wort are you collecting and what is your final batch size? I guess if you were collecting enough for a 2 hour boil I could see this happening.

This is a question that came up from a batch I did on Saturday. I used 19 lbs of grain to make a 10 gallon batch. To end up with 10.5 gallons post-boil, I needed to collect 13 gallons of 1.046 wort. I boil off 1.4 gallons per hour and did a 90 min boil. I ended up hitting the 1.046 dead on, but my last running were right at the 1.010 mark and I got just shy of 13 gallons.

 

[maltMonkey]

Wow, I don't know. I do 5 gallon batches and boil off 2 gallons per hour. When I collect 7 gallons my final runnings are still between 1.016 & 1.035.

Just out of curiosity what is your sparge water temp, what is your mash temp at the end of the sparge, and how long does your sparge take?

 

[Yuri_Rage]

Ok, you just need one more figure (estimated loss due to grain absorption) to do the math and determine the amount of water you need from the start. I'll provide a quick example, assuming your water/grain ratio is 1.25 qt/lb.

Total grain bill: 19 lbs
Pre-boil desired volume: 13 gallons
Strike water (1.25 qt/lb, approx): 6 gallons
Grain absorption (0.2 gal/lb): 3.8 gallons
Required sparge water: 10.8 gallons

 

[BierMuncher]

One trick I use but slightly

During the sparge, when the volume in the kettle hits my post boil target mark, I take a sample out of the kettle, cool it and take a reading.

This just gives me an idea of how hard I need to work to get to my targeted OG. If I'm darn close, I can ease up on sparging excess. If I'm considerably short, I'll make an extra effort to sparge to the limit to get those sugars up.

 

[JoePolvino]

I stop adding water to the mash tun when I'm about 1.5 gallons shy of my target pre-boil volume. I don't think I've ever had a tannin issue, and regularly get efficiencies in the low to mid 80's.

 

[hal simmons]

Wow, I don't know. I do 5 gallon batches and boil off 2 gallons per hour. When I collect 7 gallons my final runnings are still between 1.016 & 1.035.

Just out of curiosity what is your sparge water temp, what is your mash temp at the end of the sparge, and how long does your sparge take?

Typically sparge water temp is 175 in the HLT, Mash temp is 168 (mash out) and sparge is 45 min. This last batch that I was referring to and had the question about, I forgot to mash out. The sparge water temp was still 175 (170 by the time it hits the grains), but my mash was more like 151 and the sparge took 1.5 hours since I has some issues with my sparge arm and it was a 10 gallon batch.

 

[maltMonkey]

Next time you brew try this as an experiment:

After your sparge get a gravity reading on the final runnings. Then mix the mash up pretty good with a spoon or mash paddle and let it sit for a few minutes. Draw off some more wort and take another reading to see if the runnings aren't a lot higher.

I'm just thinking that you might be getting some channeling or getting some sugars stuck somewhere in your mash tun.

 

[hal simmons]

Next time you brew try this as an experiment:

After your sparge get a gravity reading on the final runnings. Then mix the mash up pretty good with a spoon or mash paddle and let it sit for a few minutes. Draw off some more wort and take another reading to see if the runnings aren't a lot higher.

I'm just thinking that you might be getting some channeling or getting some sugars stuck somewhere in your mash tun.

I took readings of the first gallon, the 5th gallon and then the last several gallons. My running started at 1.080ish, middle was 1.050-60ish, and the last bit was down to 1.010. I hit my target gravity of 1.046 pre-boil dead on. I have my recipes set to 85% efficiency and that's what I have gotten three times in a row.

Are you saying that if i'm buying grains based on 85% efficiency, and i'm getting 85% efficiency, I should still be getting readings in the 1.025 range for my final runnings?

 

[maltMonkey]

Are you saying that if i'm buying grains based on 85% efficiency, and i'm getting 85% efficiency, I should still be getting readings in the 1.025 range for my final runnings?

I'm definitely not an expert on the matter and I can only speak from my experience--it sounds like we have somewhat similar numbers except for the final runnings:

--I get 80% efficiency consistently (90% boil efficiency)
--I sparge for 45mins-70mins
--I collect about as much as you (I have a higher evaporation rate but only do 60min boils so I will collect 7gallons for a 5gallon batch)
--I have never had final runnings below 1.016.

 

[hal simmons]

I wonder if the difference this time was that I forgot to mash out? The last two batches I mashed out at 168, this time I forgot. That means the temp of the mash was significantly lower, which would make the sugars less willing to rinse out.

Would i make sense to calculate my recipes for 80% efficiency (or so) even though I get 85%, just so I don't risk coming that close to 1.010?

 

[ajf]

1.025 for the final runnings is an indication that there are sugars left behind that could be extracted. I always end up very close to 1.010
The experiment that maltMonkey mentioned is an excellent method for checking for channeling.
What matters far more than getting the greatest efficiency is consistency. If you consistently get the same results, you are happy with the beer, and your efficiency is reasonable or better, then what you are doing is right.

-a.

 

[jdoiv]

Would i make sense to calculate my recipes for 80% efficiency (or so) even though I get 85%, just so I don't risk coming that close to 1.010?

This is what I do. I'll just try to get a little extra volume and am usually very close to my target gravity.

If you don't have your volume by the time you gravity reaches the 1.010 threshold, I would stop the sparge and top off with a little water. Adjust your recipe down a little in efficiency and you won't have to worry about over sparging.

 

[The Pol]

I used to fly sparge until I hit 1.010 or 1.008... now I do this.

#1 Calculate my STRIKE water volume
#2 Calculate my STEP water volumes
#3 Calculate my SPARGE water volume based on how much water I have already introduced, AND how much I need to runoff to reach my pre-boil volume.

#4 Fly sparge until I run out of water, and run off my mash until it runs dry... at this point there is no more water(sugars) left in the tun, then I boil. I used to have a gallon or maybe more when I did not calculate my volumes precisely, left in my mash when I stopped sparging... perhaps leaving behind valuable sugars in solution. I also use 5.2 in my mash, and thus far have had no issues with tannins or unexpected bitterness in my beers... my EFF. is just as good if not better (77-80%)

 

[enohcs]

I always have DME around for my strters, so if I ever find my total gravity is a bit low I just add the DME as needed. Actually one of my best beers required a little extra help in the gravity department. With a pound you can expect to add about 45 points to your total gravity (adds 0.009 to your hydrometer in a 5 gal batch).