Long time batch sparger, switching to fly sparging, need some tips

[gifty74]

Long time batch sparger. Setup is a direct fired 20g Spike mash tun with false bottom and March pump for recirculation. My usual process for say a 1.070 OG beer is to follow Beersmith to get around 1.3 qt/lb of grain into the mash tun, add my grains, stir and let settle, and then begin the recirculation on top of the grain bed with a controller firing the burner, as needed, to maintain the temp I set. So with round numbers to make it simple, I'd add 5 gal of water to dough in the mash tun. After an hr I'd drain it completely, ending up with ~3.5 or so gal in the BK. Then add in the sparge water of say 4 gal. Stir like crazy, let that sit, recirculate a little, and then run that off into the BK for about 7.5 gal pre-boil.

Now, switching to fly sparging, assume the water amounts are going to pretty much be the same? Are the water calculations basically the same, with the difference being you fly sparge until the HLT is drained, and then just run out all the liquid in the MT (drain it dry)? Also, do you sparge with 190F water to raise the bed up as close to 170F as possible, or do you sparge with 170F water?

The reason I'm looking to switch is because I'm brewing a big imp stout of around 1.115 OG, so the grain bill is massive and requires ~80% of the total water for the mash due to the large size of the grist. Wouldn't really work so well I'm thinking to us 10.5 gal in the mash, and then batch sparge with 2 gal. Fly sparging seems to make sense, and been wanting to try it.

Let me know of any other tips from those that have switched, or go back and forth between the two. Thanks!

 

[Deadalus]

I won't have all the answers for you since I've been using brewing software forever and don't do the manual calculations anymore. I've never barch sparged. I fly sparge with 170F water. You wouldn't want to hit the top of the grain bed with 190F water. That would more than likely lead to astringency.

I vorlauf prior to initiating the fly sparge. This settles the grain bed and helps for clearer beer. Also, it removes most of the small bits that slip through the false bottom.

I have an EHERMS so my sparge water comes from a mostly full HLT. I could measure the water coming out but instead I just fly sparge until I hit my preboil volume. This is imprecise. I also eyeball the liquid exiting the MT to see if it is running clear. I think a more precise method is to measure the specific gravity of the MT outflow and to see if it stabilizes. Personally, I know about how much liquid is the final amount left in the MT so I try to stop fly sparging when that amount is left to top up to my preboil volume. Since you are direct firing your MT, you can just calculate the exact amount of water in your HLT to sparge with, as you wouldn't need extra water to cover a coil.

I'm brewing a dopplebock later or tomorrow but not hitting quite as high an OG. I know what you mean though about the decline in sparge amount but I don't have my computer on to check any possible differences between batch and fly sparging. I have the Beersmith app but not sure whether there's a spot to change it and not sure if it would change the amount anyway.

 

[gifty74]

Ok, so then the idea with fly sparging is not to drain the MT by the time sparging ends? Seems there would be significant sugars left if it's just a rinsing operation, and you keep the 1" above the grain bed in the MT until you have the required pre-boil vol in the BK. In the case of this imp stout, I'm only sparging with ~2 gallons (of the total 12 gals total mash/sparge water) so I'd only be rinsing for a little while, and leaving a lot of the sweet wort in there.

 

[Broken Crow]

The target of any sparge is a specific OG for a specific BK volume.. If you want to make use of the residual sugars (if any appeciable quantity), look into small-beers and/or maybe an addtional mini-mash and parti-gyle to maximize your grain expendature.

 

[gifty74]

Ok, got that. But, in Beersmith it's saying to dough in with 10.75 gal, grain will absorb 3.5, with some dead space leaving 7 gal. Sparge with 2 gal, for a total pre-boil of 9 gal (90 min boil). This means I would start sparging with the 2 gal, and when that is all drained through I would continue to let the MT drain into the BK (until all of the wort is drained from the MT) to get the 9 gal pre-boil.

 

[doug293cz]

Ok, so then the idea with fly sparging is not to drain the MT by the time sparging ends? Seems there would be significant sugars left if it's just a rinsing operation, and you keep the 1" above the grain bed in the MT until you have the required pre-boil vol in the BK. In the case of this imp stout, I'm only sparging with ~2 gallons (of the total 12 gals total mash/sparge water) so I'd only be rinsing for a little while, and leaving a lot of the sweet wort in there.

You can do it either way:

• Calculate the exact amount of water required for mashing and sparging, then after putting in the the last of the sparge water, drain the MT completely.
• Prepare extra sparge water, sparge until you reach your target pre-boil volume, and leave the MT full of dilute wort.

I haven't seen an analysis, or comparison data, that says one is better than the other, but I suspect there is very little difference w.r.t. lauter efficiency.

Leaving more sugar behind with the spent grain is just the nature of large beers. For a fixed pre-boil volume, lauter efficiency drops as the size of the grain bill increases. This is true no matter what sparge process you use. To get the same lauter efficiency with a 24 lb grain bill as with a 12 lb grain bill, you would have to double your pre-boil volume! You can improve the lauter efficiency for big beers by increasing pre-boil volume, and boiling off the extra water, but doubling the pre-boil volume is not practical.

I'm not sure you want to attempt your first fly sparge with a brew that is going to be challenging for other reasons. Better to get your process down on some normal sized beers first.

Brew on

 

[gifty74]

Thanks for the tips! I would just use the same batch sparge method I have been using, but doesn't seem it'll work by draining the tun of the first runnings, and then moving over just 2 gal to sparge with. Wouldn't even get the grain wetted again, and then have to try and recirculate and drain that off. Seems like a fly sparge is really the only way to do it, and it's not really that different than what I do now. Beersmith calculated the volumes so I should be good there. And I already did lower eff 7 pts for the big grain bill / loss of eff.

 

[doug293cz]

Thanks for the tips! I would just use the same batch sparge method I have been using, but doesn't seem it'll work by draining the tun of the first runnings, and then moving over just 2 gal to sparge with. Wouldn't even get the grain wetted again, and then have to try and recirculate and drain that off. Seems like a fly sparge is really the only way to do it, and it's not really that different than what I do now. Beersmith calculated the volumes so I should be good there. And I already did lower eff 7 pts for the big grain bill / loss of eff.

The grain will already be wet when you add the sparge water. I would look into mashing a little thicker (1.2 - 1.25 qt/lb) to shift a bit of water from strike to sparge. The other thing you can do is add some boil time to get another 0.5 - 1.0 gal of sparge water.

Beersmith does not handle lauter efficiency reduction vs. grain bill size at all. It leaves it to you to figure out what the difference in your final brewhouse efficiency will be, and adjust that in your Beersmith inputs.

I have a simulator that accurately predicts lauter efficiency changes based on grain bill weights. If you give me your grain bill and target pre-boil volume for your upcoming brew, and similar for one of your typical brews, I can tell you how much your lauter efficiency is likely to drop for compared to what you are used to.

Brew on

 

[Yesfan]

I'm not a fly sparger, so you fly spargers correct me if I'm wrong, but do you also want to sparge until the gravity coming out of the tun is close to 1.010? Seems this gives you the maximum amount of sugars without any astringency (tannins?) issues.

 

[gifty74]

The grain will already be wet when you add the sparge water. I would look into mashing a little thicker (1.2 - 1.25 qt/lb) to shift a bit of water from strike to sparge. The other thing you can do is add some boil time to get another 0.5 - 1.0 gal of sparge water.

Beersmith does not handle lauter efficiency reduction vs. grain bill size at all. It leaves it to you to figure out what the difference in your final brewhouse efficiency will be, and adjust that in your Beersmith inputs.

I have a simulator that accurately predicts lauter efficiency changes based on grain bill weights. If you give me your grain bill and target pre-boil volume for your upcoming brew, and similar for one of your typical brews, I can tell you how much your lauter efficiency is likely to drop for compared to what you are used to.

Brew on

Thanks! I did add boil time (30 min) to increase the total water needed, which raised the pre-boil volume. Working through that I realized the concept of diminishing returns. Big beers are less efficient the bigger they get. I reduced my normal brewhouse eff from 64 to 55 in Beersmith to account. So then you need more grain, which soaks up more water, and requires you add more, which drops your eff, etc etc. On this imp stout I am doing 33lbs grain with a 5.5gal finishing batch size. Pre-boil of 8.7gal to end up with 6.25 post 90 min boil. Typical would be 64 eff, 5.5 gal batch size, 1.085 OG, 18lbs grain, 7.25 pre-boil.

 

[doug293cz]

Thanks! I did add boil time (30 min) to increase the total water needed, which raised the pre-boil volume. Working through that I realized the concept of diminishing returns. Big beers are less efficient the bigger they get. I reduced my normal brewhouse eff from 64 to 55 in Beersmith to account. So then you need more grain, which soaks up more water, and requires you add more, which drops your eff, etc etc. On this imp stout I am doing 33lbs grain with a 5.5gal finishing batch size. Pre-boil of 8.7gal to end up with 6.25 post 90 min boil. Typical would be 64 eff, 5.5 gal batch size, 1.085 OG, 18lbs grain, 7.25 pre-boil.

Your 55% brewhouse eff estimate looks pretty good. I used your numbers, assumed 95% conversion efficiency, and used a triple batch sparge to estimate what you would get from a fly sparge. It came out at 65.8% lauter efficiency, 62.5% mash efficiency, and 62.5 * 5.5 gal / 6.25 gal = 55.0% brewhouse efficiency. I got your OG at 1.116.

Brew on

 

[doug293cz]

I'm not a fly sparger, so you fly spargers correct me if I'm wrong, but do you also want to sparge until the gravity coming out of the tun is close to 1.010? Seems this gives you the maximum amount of sugars without any astringency (tannins?) issues.

It is normally recommended to stop fly sparging if the instantaneous run-off SG drops to ~1.010, in order to avoid astringency issues.

However, when brewing a high gravity wort, you will likely need to stop sparging long before your run-off SG drops that low, in order to keep to a manageable pre-boil volume. In the OP's case, they need to stop run-off somewhere around 1.060 - 1.065 in order to limit pre-boil volume to 8.7 gal.

Brew on

 

[sibelman]

I've been fly sparging a long time, including with some rather high gravity brews. Though @doug293cz offers great experience and mathiness, the 1.060 figure for the last few ounces of runoff feels way off to me. I admit that my tongue is what measures this part of my process, not a hydrometer, refractometer or pH meter. I never experience really sweet runoff at the end of a sparge.

 

[kevin58]

Ok, got that. But, in Beersmith it's saying to dough in with 10.75 gal, grain will absorb 3.5, with some dead space leaving 7 gal. Sparge with 2 gal, for a total pre-boil of 9 gal (90 min boil). This means I would start sparging with the 2 gal, and when that is all drained through I would continue to let the MT drain into the BK (until all of the wort is drained from the MT) to get the 9 gal pre-boil.

Beersmith only works well when you customize your profiles. "Beersmith it's saying to dough in with 10.75 gal" you can customize those mash profiles to match your brewing procedure and are not stuck doing what the default profile is telling you... "grain will absorb 3.5" is that the absorption rate you are experiencing? You need to measure for yourself and again, use that data to customize your profiles... "with some dead space leaving 7 gal" again, have you measured the dead space? You need to know what your unrecoverable volume losses are... "Sparge with 2 gal, for a total pre-boil of 9 gal" once more, all of this is customizable and for best results needs to be.

Fly sparging is time consuming but dead simple when calculating volumes. Just keep an eye on your output and stop when you get to either the volume or gravity you want. With well tuned equipment and mash profiles both numbers should be very close to what Beersmith estimates.

 

[doug293cz]

I've been fly sparging a long time, including with some rather high gravity brews. Though @doug293cz offers great experience and mathiness, the 1.060 figure for the last few ounces of runoff feels way off to me. I admit that my tongue is what measures this part of my process, not a hydrometer, refractometer or pH meter. I never experience really sweet runoff at the end of a sparge.

Be nice if you had some data, and specifics about the mash/lauter it was collected from, to support your assertion. I always welcome data that will either validate, or point out weaknesses in, my simulation. To date, there have been no significant discrepancies found.

Brew on

 

[sibelman]

Be nice if you had some data, and specifics about the mash/lauter it was collected from, to support your assertion. I always welcome data that will either validate, or point out weaknesses in, my simulation. To date, there have been no significant discrepancies found.

Brew on

Fair enough. I haven't made a full barley wine strength beer for about a decade, and (as reported) my 'data' are highly subjective. I did collect 9.7 gallons.

I know this thread is about mash/lauter, but... Any yeast recommendations for a ~1.125 barley wine that has a hope of finishing dry?

 

[JohnDBrewer]

I fly sparge on a RIMS system and use Beersmith. I loose 1.33 gallons/10lbs of grain to absorption. I mash at 1.25qts/lbs. Before I sparge I raise the grain bed to 168-172 degrees and let it rest for 10-15 minutes then sparge with 172 degree water to hit my target volume in the BK. For a 5g batch this takes about 30 minute to sparge, the slower the better. Twice that for a 10g batch. Once I get a couple of inches of wort in the BK I start heating it so when the sparge is done I'm boiling. Again low and slow so you do not scorch it.

With a big beer I always have pretty low efficiency on that beer, just the nature of not being able to run enough sparge water through the grain bed. Once I hit the preboil volume in the BK for the first beer (the big one), I continue sparging into a separate pot to make a second beer (partigyle). This second beer is the only brew I ever try to measure the final running to make sure I do not over-sparge, i.e. SG goes below 1.010. If the first beer is big enough, I can usually get enough for 5 gallons of a second beer. I have even added water and DME to get my second beer up to enough volume and OG to make sure I get 5 gallons of beer.

With an imperial stout, the second beer can be a nice porter.

 

[Climb]

@sibelman - You might want to consider San Diego Super yeast (WLP090) for a high gravity American barley wine. It is a neutral yeast with an alcohol tolerance speced up to 15%.

 

[Deadalus]

Ended up waiting until yesterday to brew the dopplebock. I brew on a 3 keggle 2 pump EHERMs. I was only brewing a 6 gallon batch. I had a number of tasks to complete yesterday brewing related so I was able to take my time at points during the brew session. I decided I was going to do was to slow the fly sparge down to a trickle. I don't have marks for under 4.5 gallons, that's where my sight glass starts. I'd say it was as slow as 2 gallons/hour, it was a glacial trickle. In the meantime, I had some kegs to clean, I purge four kegs, and I need to transfer my Munich Helles because I was going to put this brew right on the yeast cake. Mashing and everything prior went well up to the fly sparge where I ran into various issues, none insurmountable the brew made it into the carboy.

Since it was a smaller batch, I had room to oversparge. I was planning on an extra gallon in the BK. Over the course of this brew and the last, I have made some equipment changes. I added on a float valve and ball to the MT last brew and that went smoothly. However, the female QD I have on the float valve for some reason was loose at the connection. I have male QD's on my rotating sparge arm and recirculation manifold that go into that female QD. I wasn't sure they were properly mated but no problems last time. Heavy leakage on the connection for the sparge arm prevented use of the ball float. I had to use a higher flow to the MT to get the arm to spin and I ended up overshooting, my extra gallon became two. I had checked the gravity at what would have been my regular preboil volume (one gallon over) and it was 1.045. I did not get a final reading coming out of the MT.

This left me with 3 gallons to boil off, with 9 gallons in the keggle. In the 60 brews in this keggle, 3/4 of which have been electric, I have only once had a very tiny boil over the cutout and that was when it was gas-fired. Now about 80-90% where 6 gallon batches but I know to be careful with bigger batches. I boiled off the extra two gallons without any issues by keeping the power at 60%. In the meantime, I finished cleaning some kegs and started purging a batch of 5. Besides the slow sparge and oversparge, I was planning on overboiling about a half to full gallon. This way I should hit the target and if needed, top off if the gravity was more than expected. I put the power at 100% and tossed in my 60 minute hops. Exhaust fan was on high, music was blaring. So there I was, tilting my MT with one hand and scooping grain out with the paddle into a bucket on the floor and I see tannish runoff water pooling on the brew stand. First thought was, "What's leaking out of the MT"?? Nothing. Plenty spilling out of the BK however! And one of the changes was a Hop Stopper 2, so there were free-floating hops blown out all over the table and BK too. It was a mess but probably not more than a pint. I adjusted the power down but kept it vigorously boiling.

I ended up with about 5.25-5.5 gallons for a six gallon batch. I just managed to keg the Helles prior to finishing up chilling and I put the dopplebock onto the yeast cake in that carboy. I've never done it this way before as I usually don't brew back to back styles with the same yeast. Seemed like a good pair to try it with. I wasn't exactly sure about the depth of the yeast cake and trub as I had pressurized the purged kegs and forgot to release the pressure when I started the pressure transfer of the Helles. Stupid move as I had cold crashed that Helles for a couple weeks! With the new Hop Stopper, I had about 1/2 gallon left in the BK too. I had under 3 oz of pellet hops in the brew but could pull that last bit out. I had chilled down to 60 and even whirlpooled the trub for a bit as I was washing equipment but I couldn't get the pump to pull the rest at the low flow required for the Hop Stopper. Could have been the high gravity clogging the mesh as well, it was like syrup.

Final gravity was 1.098 on roughly 5.25 gallons and should have been 1.096 for 6 gallons. If you can't tell, I don't always measure every step to get the different efficiencies. I use a slightly conservative 85% brewhouse efficiency and this batch was reduced to 76% brewhouse efficiency. The Helles was 88.6% on the measured brewhouse efficiency. It was about 12 hours when I checked it again this morning and it was already bubbling away.

Short story is super slow sparge, oversparge, then increase boil off (correct if possible). It took a lot more time but I just filled the time with other tasks. Maybe not the best way, probably easier to increase the grain bill but if somehow limited there's a couple of items to try. An extra pot could be used to oversparge and boil off. It tasted really wonderful after the hydrometer reading.

 

[sibelman]

It is normally recommended to stop fly sparging if the instantaneous run-off SG drops to ~1.010, in order to avoid astringency issues.

However, when brewing a high gravity wort, you will likely need to stop sparging long before your run-off SG drops that low, in order to keep to a manageable pre-boil volume. In the OP's case, they need to stop run-off somewhere around 1.060 - 1.065 in order to limit pre-boil volume to 8.7 gal.

Brew on

So today was brew-a-barley-wine day, motivated in part by the gap between my recollections and Doug's model of lauter gravity/volume. I fit 21 pounds of 2-row base malt in my Chapman Thermobarrel mashtun, with about 26 quarts, aiming (successfully) for 150°F. I recirculated for about an hour and then raised the temp to 168°F and began my fly sparge, aiming (successfully) for a boil volume of 8.7 gallons.

Because my curiosity was piqued, I took samples of first runnings at 1.091, mid-runnings also at 1.091 (!?), 1.034 after collecting 7.5 gallons, and 1.025 at the end of run-off (8.7 gallons). All samples were measured with a hydrometer at ~67°F. I kept the sparge very slow, about 90 minutes all told. At the end there was still discernible sweetness though the color was pretty darn pale.

Pre-boil gravity was 1.078, which I calculate as about 87% lauter efficiency. This is in line with my previous experience with more moderate gravity brews, and is rather unexpected 'cuz high gravity generally means lower efficiency. Measurement error can't be excluded, of course. The really slow sparge may partly explain the fine efficiency. I boiled down to 5.8 gallons, whirlpooled and chilled, collecting about 5.2 gallons at OG 1.102, so a brewhouse efficiency around 70% (per Brewer's Friend recipe calculator).

I'm hoping for a reasonably dry English barley wine result, and I've pitched a 2l Imperial Pub starter to be followed by US-05 on day 3 as @Miraculix suggested elsewhere. I plan to move the brew to a keg (purged with fermentation gas) for secondary, after giving the US-05 some time to do what Pub can't.

@doug293cz, I'm wondering why my lauter was (as I intuited it would be) so much more nearly "complete" than your model predicts. I know there are many variables, but...?

 

[Bobby_M]

@doug293cz, I'm wondering why my lauter was (as I intuited it would be) so much more nearly "complete" than your model predicts. I know there are many variables, but...?

One possibility is channeling. You can test by stabbing a spoon or mash paddle to the bottom of the tun after you're done collecting wort and do one full revolution of stirring gently then run off a little more wort. If the gravity of that wort is higher than the last measured runnings, channeling happened at least a little. In a perfect world, the fly sparge gravity gradient is linear from top to bottom but it's rarely perfect.

 

[Bobby_M]

Because my curiosity was piqued, I took samples of first runnings at 1.091, mid-runnings also at 1.091 (!?),

At the time that you measured "mid runnings" you were still draining "mash gravity" wort that was just moving down the column. The point at which gravity starts dropping is when the sparge water finally makes it to the bottom with whatever sugar it picked up on the way down.

 

[doug293cz]

So today was brew-a-barley-wine day, motivated in part by the gap between my recollections and Doug's model of lauter gravity/volume. I fit 21 pounds of 2-row base malt in my Chapman Thermobarrel mashtun, with about 26 quarts, aiming (successfully) for 150°F. I recirculated for about an hour and then raised the temp to 168°F and began my fly sparge, aiming (successfully) for a boil volume of 8.7 gallons.

Because my curiosity was piqued, I took samples of first runnings at 1.091, mid-runnings also at 1.091 (!?), 1.034 after collecting 7.5 gallons, and 1.025 at the end of run-off (8.7 gallons). All samples were measured with a hydrometer at ~67°F. I kept the sparge very slow, about 90 minutes all told. At the end there was still discernible sweetness though the color was pretty darn pale.

Pre-boil gravity was 1.078, which I calculate as about 87% lauter efficiency. This is in line with my previous experience with more moderate gravity brews, and is rather unexpected 'cuz high gravity generally means lower efficiency. Measurement error can't be excluded, of course. The really slow sparge may partly explain the fine efficiency. I boiled down to 5.8 gallons, whirlpooled and chilled, collecting about 5.2 gallons at OG 1.102, so a brewhouse efficiency around 70% (per Brewer's Friend recipe calculator).

I'm hoping for a reasonably dry English barley wine result, and I've pitched a 2l Imperial Pub starter to be followed by US-05 on day 3 as @Miraculix suggested elsewhere. I plan to move the brew to a keg (purged with fermentation gas) for secondary, after giving the US-05 some time to do what Pub can't.

@doug293cz, I'm wondering why my lauter was (as I intuited it would be) so much more nearly "complete" than your model predicts. I know there are many variables, but...?

Looks like data I can use to see how well my model works for fly sparging. Do you have any idea what the +/- uncertainty is for your volume measurements?

Brew on

 

[sibelman]

Thanks for your responses, Bobby & Doug.

I've got half gallon markings in my kettle and fermenter and 1 gal marks on HLT sight glass (not really relevant), so I feel able to get about +/- 0.1 gallon precision. My hydrometer readings are +/- .001, I'd say.

The channeling test idea is interesting, but channeling seems least likely in a deep mash bed like today's monsta mash. Too, I've most heard it discussed in terms of low lauter efficiency.

 

[doug293cz]

So today was brew-a-barley-wine day, motivated in part by the gap between my recollections and Doug's model of lauter gravity/volume. I fit 21 pounds of 2-row base malt in my Chapman Thermobarrel mashtun, with about 26 quarts, aiming (successfully) for 150°F. I recirculated for about an hour and then raised the temp to 168°F and began my fly sparge, aiming (successfully) for a boil volume of 8.7 gallons.

Because my curiosity was piqued, I took samples of first runnings at 1.091, mid-runnings also at 1.091 (!?), 1.034 after collecting 7.5 gallons, and 1.025 at the end of run-off (8.7 gallons). All samples were measured with a hydrometer at ~67°F. I kept the sparge very slow, about 90 minutes all told. At the end there was still discernible sweetness though the color was pretty darn pale.

Pre-boil gravity was 1.078, which I calculate as about 87% lauter efficiency. This is in line with my previous experience with more moderate gravity brews, and is rather unexpected 'cuz high gravity generally means lower efficiency. Measurement error can't be excluded, of course. The really slow sparge may partly explain the fine efficiency. I boiled down to 5.8 gallons, whirlpooled and chilled, collecting about 5.2 gallons at OG 1.102, so a brewhouse efficiency around 70% (per Brewer's Friend recipe calculator).

I'm hoping for a reasonably dry English barley wine result, and I've pitched a 2l Imperial Pub starter to be followed by US-05 on day 3 as @Miraculix suggested elsewhere. I plan to move the brew to a keg (purged with fermentation gas) for secondary, after giving the US-05 some time to do what Pub can't.

@doug293cz, I'm wondering why my lauter was (as I intuited it would be) so much more nearly "complete" than your model predicts. I know there are many variables, but...?

Sorry I took so long to get back on this.

My existing simulation model is based on batch sparging, and the original spreadsheet allowed for 0 to 3 batch sparge steps. Previous data I have received from a fly sparger on HBT indicated that a good fly sparge is somewhat more efficient than a triple batch sparge. And since lauter efficiency increases with increasing number of batch sparge steps, it occurred to me that I might be able to model a fly sparge as a large (essentially infinite) number of small batch sparges. So, I modified my spreadsheet to allow up to 15 batch sparge steps.

Armed with my modified spreadsheet, I fed in the parameters from your barley wine brew session. The parameters I used are as follows:

• Grain weight: 21 lb
• Weighted ave grain potential: 37 pt/lb
• Grain moisture content: 4%
• Strike water volume: 6.5 gal (26 qt)
• Pre-boil volume: 8.7 gal
• Post-boil volume: 5.8 gal
• Grain apparent absorption rate: 0.11 gal/lb (I would have used 0.12 for a faster fly sparge)

In order to get your first runnings SG to come out at 1.091, your conversion efficiency came out at 93.9%

After running off 7.5 gal the instantaneous runnings SG came out to 1.0367, in pretty good agreement with your measured 1.034.

End runnings (after 8.7 gal) SG came out to 1.0263, again in good agreement with your 1.024.

The calculated pre-boil SG was 1.070, which is lower than your 1.078. But the calculated OG (post-boil) was 1.104 vs. your 1.102. 8.7 gal of 1.078 wort boiled down to 5.8 gal should have an OG of 1.117 (8.7 * 78 / 5.8 = 117.) So, I suspect that your OG measurement and/or pre-boil volume measurement was in error (wort could have been stratified due to inadequate mixing before sampling.)

My simulation estimated your lauter efficiency at 87%, and your mash efficiency at 81.65% (0.939 * 0.870 = 0.8165). The estimated brewhouse efficiency would be 81.65% * 5.2 gal / 5.8 gal = 73%.

I believe these calculations validate the use of many small batch sparges to simulate a fly sparge.

When I estimated OP's final runnings gravity at 1.060 - 1.065, that was based on a 33 lb grain bill rather than the 21 lb that you used. That extra 12 lb of grain makes a huge difference in lauter efficiency, and final runnings gravity.

Brew on

 

[sibelman]

Doug, your mathematical model sounds like a reasonable approximation of reality. Measurement error could explain the divergences (though generally we look to create and refine models that correspond with data rather than the other way around ). More data would perhaps further clarify the situation, but a decent model is useful even though variations in equipment and process will always cause some variance from predictions.

It's fun to quantitatively assess what we do with an eye toward better results. Up to a point.

Speaking strictly for myself, I accept that each brew will have some variation. In the range between the lab and the kitchen, my homebrewing leans more toward the kitchen. I embrace ingredient, process and equipment changes that make my brew day better and, especially, that make my beer tastier. I don't much worry about "hitting my numbers."

 

[TheMadKing]

disregard, mispost

 

[doug293cz]

Measurement error could explain the divergences (though generally we look to create and refine models that correspond with data rather than the other way around ). More data would perhaps further clarify the situation, but a decent model is useful even though variations in equipment and process will always cause some variance from predictions.

It's not quite as simple as you make it out. All measurements have errors, and most models have simplifications that can affect their accuracy differently in different situations. Before using a set of measurements to decide that a model needs to be modified, you need to understand the quality (accuracy, precision, repeatability) of the measurements. If the discrepancies between model predictions and measured results are within the uncertainty created by the possible measurement errors, then there is no justification for modifying the model. Having multiple sets of measurements is preferred, as statistical analysis can reduce the uncertainty about actual values for the collected data, which gives a better basis to compare with model predictions.

The model in my simulator has very few simplifications when used for batch sparging. For the results to be valid:

• No conversion must happen after initial run-off begins (it's possible to detect this condition if it occurs.)
• The wort in the mash must be fully homogenized before each run-off (initial and sparge) (it is not possible to detect if this condition is violated.)
• The model assumes that grain absorption is the same for all run-offs. This could be modified if there is actual data on the absorption for each run-off.

When it comes to using many small batch sparges to simulate a fly sparge, there is much more uncertainty. However, given that for the time being, we are comparing a single set of measurements, the discrepancies between the model and measurement are within the uncertainty due to measurement quality, and at least one of the measurements is known to be seriously in error. There is no basis at the current time to say the model does not have good predictive capability, even for fly sparging.

Speaking strictly for myself, I accept that each brew will have some variation. In the range between the lab and the kitchen, my homebrewing leans more toward the kitchen. I embrace ingredient, process and equipment changes that make my brew day better and, especially, that make my beer tastier. I don't much worry about "hitting my numbers."

I don't advocate being a slave to numbers either. However, using models (that have been subject to some level of validation) to predict what is likely to happen in situations significantly different than your normal practice can be quite enlightening. In cases where you are doubling or tripling the grain bill for the same batch size, it's good to have a model to tell you what to expect. Unfortunately, most brewing software does not have the ability to predict what happens to lauter efficiency as grain bill to pre-boil volume ratio increases, and leaves the brewer to their own devices to guess how much of an adjustment to their typical efficiency is needed. I believe my model is the best currently available to homebrewers to predict effects on mash and lauter results given their equipment profiles, and typical process.

Brew on

 

[sibelman]

I applaud your analytical rigor, Doug. Thank you for laying out your model's relationship to my fly sparging experience. I concur with your thought that a many-small-batch model would be expected to well approximate fly sparging.

It also reminds me of how, back in the day, I added sparge water a cupful at a time to roughly maintain the level in the mashtun. A slightly batch-ish fly sparge.

Of course, I did not intend to imply that the limited and low-precision data from my recent brew day suggest any change to your model.

Cheers.

 

[gifty74]

Wow guys, thanks for all of the discussion & ideas here. I finally have a day free to brew, so think I'm going to just go for it. Never fly sparged, but my system is pretty set up for it, so will just take my time, sparge slow, and see how efficient I can get it. Big grain bill that will max out my 15gal MT. Plan to get ~9 pre-boil and boil long to condense it down. Should add some complexity to this imp stout recipe. Read at length on balancing roast malts (bitterness) with higher FG due to the very high OG, and think I have a good malt bill to do so. It'll be a long day, but I've been wanting to master this style and today will be rev 0. I will be sure to update back here with the session results, and let you know how it went, OG, etc etc. Excited!

 

[dmaxweb]

I fly sparge and calculate the water needed plus 1-2 gallons just in case. My target is, within reason, draining the MT. I pump directly from the MT to the BK so I need to really throttle back the pump to get the last of it without creating a vacuum. I'm in the process of building a lauter grant to help with that as opposed to catching the last runnings in a bucket and pouring into the boil. My process otherwise is pretty automated and generally routine. I'm getting right at 92% efficiency now.