What BIAB brewing actually is (Mythbusting for traditionalists)

[Willy]

The thermo I use has a 2" probe, the end of which is rounded. Never had a snag issue.

This is my replacement for the original longer skinny poke the bag disaster maker.
https://www.amazon.com/gp/aw/d/B08F3FB2GG?psc=1&ref=ppx_pop_mob_b_asin_image

 

[Closet Fermenter]

This is my replacement for the original longer skinny poke the bag disaster maker.
https://www.amazon.com/gp/aw/d/B08F3FB2GG?psc=1&ref=ppx_pop_mob_b_asin_image

Oh, that’s perfect! Appreciate your sharing the link!

 

[Broken Crow]

This is my replacement for the original longer skinny poke the bag disaster maker.
https://www.amazon.com/gp/aw/d/B08F3FB2GG?psc=1&ref=ppx_pop_mob_b_asin_image

Why not just skip the thermometer altogether? Unfortunately, your lnk doesn't work in Canada and I get a search page of a bunch of short themometers, most of which have brass probes.. not something I'd want in my kettle.
A kettle mounted thermometer is useless during the mash, and if you have an electronic temp control unit a thermometer becomes redundant and on a gas-fired system what's the point of even looking at the thermometer when you want to adjust your boil by eye anyway?
Not looking for an argument... I had entered the hobby and simply because everyone had a thermometer on their gear it seemed like it should be there, but the only temp monitoring that has ever been of practical value to me was on the recirculation temp and not even mounted on the kettle or on a handheld thermometer probing the mash. I'm actually going nuts trying to source and economical new kettle that omits the port for a themometer that I'll never use.

 

[Willy]

Why not just skip the thermometer altogether? Unfortunately, your lnk doesn't work in Canada and I get a search page of a bunch of short themometers, most of which have brass probes.. not something I'd want in my kettle.
A kettle mounted thermometer is useless during the mash, and if you have an electronic temp control unit a thermometer becomes redundant and on a gas-fired system what's the point of even looking at the thermometer when you want to adjust your boil by eye anyway?
Not looking for an argument... I had entered the hobby and simply because everyone had a thermometer on their gear it seemed like it should be there, but the only temp monitoring that has ever been of practical value to me was on the recirculation temp and not even mounted on the kettle or on a handheld thermometer probing the mash. I'm actually going nuts trying to source and economical new kettle that omits the port for a themometer that I'll never use.

Totally agree. This was a solution long ago when I mashed using a brew kettle. I agree - I simple thermometer probe hanging off the side is probably the best option.

 

[Closet Fermenter]

Why not just skip the thermometer altogether? Unfortunately, your lnk doesn't work in Canada and I get a search page of a bunch of short themometers, most of which have brass probes.. not something I'd want in my kettle.
A kettle mounted thermometer is useless during the mash, and if you have an electronic temp control unit a thermometer becomes redundant and on a gas-fired system what's the point of even looking at the thermometer when you want to adjust your boil by eye anyway?
Not looking for an argument... I had entered the hobby and simply because everyone had a thermometer on their gear it seemed like it should be there, but the only temp monitoring that has ever been of practical value to me was on the recirculation temp and not even mounted on the kettle or on a handheld thermometer probing the mash. I'm actually going nuts trying to source and economical new kettle that omits the port for a themometer that I'll never use.

About the only thing I use the boil kettle thermometer for is checking the temperature after the boil is finished and I am chilling the wort. I am not recirculating, but have had good results anyway; hitting my numbers with kits, or unmodified recipes I find.

While we’re talking thermometers, what’s the best one you have found? I have two “lab style” thermometers, the dial thermometer on my kettle, a thermometer on my mash tun, an infrared thermometer, and a floating dairy thermometer; none of them agree!

I would really like to make sure my mash temperature is right.

 

[Broken Crow]

checking the temperature after the boil is finished and I am chilling the wort. I am not recirculating

Ok..that's where we differ: I have an inline dial thermometer on the output of my pump and I recirculate through a CFC,
As to the 'best'.. An infrared thermometer is subject to breezes and convection currents and not very good at assessing any more than the outer portion of a large volume. The cheap pen-type are pretty consistant these days and most of the time they are accurate or at least have a consistant offset; I borrowed a friend's very expsensive Fluke with a long wired probe to calibrate my dial-themometers and compare to my floating mercury thermometer: The cheap and popular floating mercury themometer was dead accurate, so until I replace by cheap broken pen, it serves the mash (with golves on ) I had 3 dial themometers, all from different sources and after calibrating, two of them remained accurate at both cold and hot temps, but one had a curve of increasing inaccuracy so I smashed it and threw it out. (I have a bad tendency to save everything I might find another use for someday, but when it comes to critical measurements, if it lets me down it meets the hammer before I can second-guess myself and throw it in with my extensive 're-purposable' collection).
I have an expensive Fluke themometer on my long-term (but not critical) shopping list.
https://www.fluke.com/en-us/product/temperature-measurement/ir-thermometers/fluke-51-ii
Honestly though; There are so many cheap pen-style ones available that have proven themselves to a number of users on here,
I'm pretty sure the "Thermopen" is the most respected model. Just give every thermometer you use the ice-water and boiling water test.

 

[MaxStout]

About the only thing I use the boil kettle thermometer for is checking the temperature after the boil is finished and I am chilling the wort. I am not recirculating, but have had good results anyway; hitting my numbers with kits, or unmodified recipes I find.

While we’re talking thermometers, what’s the best one you have found? I have two “lab style” thermometers, the dial thermometer on my kettle, a thermometer on my mash tun, an infrared thermometer, and a floating dairy thermometer; none of them agree!

I would really like to make sure my mash temperature is right.

Thermoworks makes a nice, fast-read digital thermometer with a 12" or 24" probe. I have the 12, like it a lot.

https://www.thermoworks.com/t-grip/

 

[Bobby_M]

One of the things I'm grateful for is that I get to build a lot of systems. The operation here is small enough that I'm actually the guy doing the building/welding. I get to make quick adjustments to the design based on a user's situation; e.g. my sink is on the right and the electrical outlet is on the left. I'm digressing a bit here, but the point is that I'm not stuck on a system design/layout for the sake of operational (business/production) efficiency so I can immediately pivot if an improvement is realized. Selfishly, I also get to build myself the newest design and sell the older one as a demo/used kettle.

Here's what I know so far..

• Bottom drain is VERY NICE. A 10 gallon kettle can be easily tossed around for cleaning. As you go to 15 and 20 gallon sizes, much less so, even if you have a huge sink right next to your table. My 24" x 36" sink is 5 inches away from my 15 gallon kettle. However, with all the ports and stuff cantilevered out from the kettle, even tipping it over into the sink is a pain. If you have all TC stuff, you can disassemble quite a bit before hand, but that makes some mess in the process. Even at the 15 gallon size, I switched to a bottom drain. The kettle never has to move and I don't disassemble anything. One bonus benefit is how easy the pump primes when fed from a bottom drain. There's no mid-line air bubble like in a siphon tube side drain.
• By a large margin, a 5-5.5Kwatt fired eBIAB RIMS kettle is the fastest heating system design there is, beating out RIMS(tubes), HERMS and direct fire. That includes step mash moves as well. It's not faster than water or steam infusion step mashing but those have their own problems.
• Full volume mashing with no sparging is generally a low extraction efficiency in the realm of system designs. It's a fact so if you're transitioning from 3V sparged systems, don't bother trying to duplicate a recipe without making any adjustments. If you don't, you'll be posting about not hitting your numbers. YOUR NUMBERS are different now. Start with 65% brewhouse or 73% mash efficiency and use the SCALE function on your software. if you're lo-tech and don't use brewing software, just increase your grain bill by 10%. I personally like erring on the side of overshooting my preboil gravity target because it's easy to dilute the wort with water and dump excess volume but it's just as easy to keep a bag of light DME on hand to make corrections. It's also fine to just roll with whatever you get.

 

[day_trippr]

Thermoworks makes a nice, fast-read digital thermometer with a 12" or 24" probe. I have the 12, like it a lot.

https://www.thermoworks.com/t-grip/

And I have the 24" long version for my 20 gallon kettles and would be sad to brew without it...

Cheers!

 

[toxdoc49]

I wanted to address a few things that have been touched on in plenty of threads in the past. The readers I'm mostly addressing are those who think Brew in a Bag as a process is inferior, makes subpar beer, or is "okay, but really just a stepping stone to REAL brewing". This is probably going to be pretty disjointed, fair warning.

BIAB is an all grain brewing method where the mash is held in a porous bag or basket within boil kettle. Post mash, the spent grain is removed from the boil kettle, leaving only wort behind. The preboil volume of wort is usually achieved by using enough initial water to yield the desired volume. This is known as full volume mashing. In some cases, the mash is performed thicker and a sparging step is added after pulling the bag or basket. The reasons and/or mechanics of sparging are not really the point of this post so I'll skip it. The premise however is that the defining characteristic of BIAB is that the grain is contained in a mesh "vessel" within the boil kettle and the grain is remove from the wort (not vice versa like in a typical mash tun). That's it. No... I'm serious. That is it.

Some people will read that and think, "yeah, I get it, what's the point?". It's painfully obvious that so many people, even long time regulars here at HBT do not get it based on the comments they make in various threads. Here are some random things you'll find.

1. BIAB is not real all grain brewing (as an outright proposition). False. All grain brewing is very simple to understand. You derive most, if not all, of your wort's sugars from cereal grains through the mashing process. BIAB relies on the same mashing and ends up with the same wort. I get why this is perpetuated. Even HBT has BIAB as a separate forum from All Grain Brewing. If anything, BIAB should be a sub forum to All Grain Brewing.

2. I'll just BIAB until I can afford to upgrade to an all grain system (or some other disconnection of terms due to ignorance). False. See above. BIAB is all grain brewing. You probably mean that you have been drooling over pictures of shiny brewing systems that feature multiple tanks and pumps and you have it in your head that a system like that is the end game for "reasons". That's misguided, but fair. How would you account for the hundreds of people who have owned 3 vessel systems and switched to BIAB?

3. BIAB makes cloudy beer. False. BIAB makes cloudier preboil wort. That's it. My BIAB wort going into the fermenter is as clear as any 3 vessel system beers I've ever made.

4. BIAB is less efficient. Sometimes. Woah, we actually hit on an actual piece of controversy. When you run BIAB as a full volume, no sparge process, it does tend to be lower mash/lauter efficiency than an inherently sparged system. BIAB brewers typically report a mash/lauter efficiency between 65-80% with some fringe examples a bit higher. 3 vessel brewers average more than that. The ultimate impact of these efficiency differences will typically amount to 1-2 extra pounds of grain to buy.

5. I like operating a 3 vessel system because it feels more legitimate. Subjective. If your goal is to prepare yourself for brewing at commercial scale, this is probably the most reasonable argument against BIAB brewing. However, a lot of times this type of argument comes up, it's from people who don't aspire to go pro and have never brewed on anything other than a 3 vessel. My opinion is that the most legitimate brewing method is the one that yields the highest quality beer. There are probably plenty of good reasons one may enjoy 3 vessel brewing but just be aware of tunnel vision.

6. Pulling the bag out is difficult and it makes a mess. Poor planning, poor execution. The BIAB process has this known requirement of pulling the spent grain out and you have to take that into account before brew day. The majority of people who try BIAB and then claim it sucks are the same people who try pulling 40 pounds of hot dripping mess out of the kettle by hand, alone. Shame on you, do not pass Go, do not collect $200. Get yourself an overhead with a ratchet strap or locking rope pulley to suspend the bag over the kettle to drain. Long story short, if I get more than a drop of wort on myself or on the floor, that's a lot.

7. Full volume mashing is sloppy, imprecise, has conversion problems, is too thin, [insert some other technical mashing mechanic problem]. What? I've seen all kinds of random statements about how mashes thinner than 2qts per pound will never convert or how the pH will be so screwed up that you'll extract tannins. The tannins argument also comes up regarding the finer crush that BIAB often uses. First, there is most decidedly no issue with conversion with full volume mashes as long as the grist is of typical diastatic power (typical mix of malted base malts with limited adjuncts). The topic of tannin extraction is primarily a topic of mash pH and the water chemistry/grist makeup that gets you there. This topic is in no way tied specifically to the mash vessel. The bottom line is that good brewers know their water and what kind of mash pH to expect on every one of their batches. This goes for all brewing methods. BIAB full volume mashing actually has the most stable mash pH because there is no sparging. Typically tannin extraction occurs when sparging with alkaline water, if the mash pH itself wasn't already out of range.

8. I like the repeatability and temperature stability of more sophisticated mashing systems so BIAB is definitely NOT for me. Misinformed. You thought BIAB was limited to a paint strainer bag dunked in a greasy turkey fryer pot but you're wrong. My BIAB system holds rock solid mash temps for as long as I want. I can step mash to precise steps faster than a 3 vessel HERMS or RIMS.

9. BIAB makes subpar beer. False. Everything being equal of course. Let me be very clear. BIAB is a wort production process just like a fly sparged HERMS regulated mash is a wort production process. If you find some correlation between beers brewed with the BIAB process and a lower quality end beer, that's just bad brewing technique. Sure, that's easy to claim. If BIAB is by definition inferior, there would be no examples of BIAB brewers consistently doing well at competitions, especially competitions entered by both BIAB brewers and traditional 3 vessel brewers. Ok, let's look at that.

Here are the final standings for the 2020 New Jersey Homebrewer of the Year. Brewer's are awarded points for medaling in three qualifying competitions throughout the year. The guy that took first place works at BrewHardware and I built his BIAB system about 2 years ago. The guy in 3rd place is also a friend and I built his BIAB rig about 2 years ago. I'm not positive but I'm pretty sure the 2nd place guy uses a 3 vessel system. Certainly the 4th and 5th place brewers are traditional 3 vessel brewers.

View attachment 707560

Ok... here's the previous year. The first place guy... not sure. 2nd and 3rd place, BIAB brewers. I know because I built their kettles.

View attachment 707561

Ok, the last year I have records for. Not sure the method for 1st and 2nd place but 3rd and 4th definitely BIAB.
View attachment 707562

The point is, this isn't just getting lucky at a comp. This is consistent, high caliber brewing. Can we put this subpar BS argument to bed yet?

Edit to add a little more data here. In case anyone was wondering what styles the winning brewers brew, especially for naysayers that contend some styles can't be brewed via BIAB properly, here are some stats.

Larry B's year:
Gold: American Brown
Silver: Altbier
Gold: NEIPA
Silver: German Pilsner
Silver: Kellerbier
Gold: American Pale Ale
Silver: NEIPA
Gold: American Pale Ale
Gold: Altbier
Silver: Belgian Blonde
Silver: Kellerbier
Bronze: NEIPA

Tom D's year:
Gold and 1st Best of Show for a Gose
Silver: Munich Helles
Bronze: Belgian Trippel
Gold: Double IPA
Silver: German Pilsner
Silver: NEIPA
Gold: NEIPA
Bronze: Rye IPA
Bronze: Baltic Porter

Great post! I use a very simple BIAB system and most of the work is manual. One thing I do (to point #4) is dunk sparge after mashing. So I am not using a full volume for mashing. In my limited experience I think dunk sparging increases the efficiency. I am only using a single vessel for mashing and another vessel to dunk sparge. Some use a cooler for dunk sparging. Of course, we all know there are many ways to brew. I hope to at least upgrade to a vessel such as the Grainfather, but, that said, I still appreciate the knowledge gained from doing things manually.

 

[Bobby_M]

Great post! I use a very simple BIAB system and most of the work is manual. One thing I do (to point #4) is dunk sparge after mashing. So I am not using a full volume for mashing. In my limited experience I think dunk sparging increases the efficiency. I am only using a single vessel for mashing and another vessel to dunk sparge. Some use a cooler for dunk sparging. Of course, we all know there are many ways to brew. I hope to at least upgrade to a vessel such as the Grainfather, but, that said, I still appreciate the knowledge gained from doing things manually.

Sparging of any variety is a guaranteed boost in efficiency. Since my kettle can handle the full volume and I'm not burdened by the need for shoestring budget, I just stick with the lower efficiency for simplicity and ease of cleanup.

 

[Willy]

Sparging of any variety is a guaranteed boost in efficiency. Since my kettle can handle the full volume and I'm not burdened by the need for shoestring budget, I just stick with the lower efficiency for simplicity and ease of cleanup.

On a "usual" 5 gal batch, ABV at 6% - what is the cost increase of grains to retain the same efficiency ? (Say, sparge gets you 73% and no sparge? Don't know, maybe 62%% )

Guessing - 2-3 dollars. But I don't know. Don't care enough to do the math - I bet you might know @Bobby_M - too many variables I know, but a range. As little as $1 to ?

 

[mac_1103]

I think the rule of thumb is that a single batch sparge will increase lauter efficiency by 8%. The difference between 65% and 73% efficiency is about a pound and a half of pale ale malt on a 1.060 SMaSH. So two bucks when I buy in bulk from my local maltster.

 

[doug293cz]

On a "usual" 5 gal batch, ABV at 6% - what is the cost increase of grains to retain the same efficiency ? (Say, sparge gets you 73% and no sparge? Don't know, maybe 62%% )

Guessing - 2-3 dollars. But I don't know. Don't care enough to do the math - I bet you might know @Bobby_M - too many variables I know, but a range. As little as $1 to ?

Ok, I ran a simulation with the following inputs:

Target OG : 1.060​

Target post-boil volume : 5.5 gal​

Weighted average grain potential : 37 pts/lb​

Conversion efficiency : 95%​

Total boil-off : 1.0 gal​

Grain absorption rate : 0.08 gal/lb​

For an optimal single batch/dunk sparge the grain required is 10.85 lb, and the mash efficiency is 85.8%

For a full volume, no-sparge mash the grain required is 12.31 lb, and the mash efficiency is 75.6%

If we change the target OG to 1.040, then:

For an optimal single batch/dunk sparge the grain required is 6.85 lb, and the mash efficiency is 90.3%

For a full volume, no-sparge mash the grain required is 7.54 lb, and the mash efficiency is 82.1%

I used my mash and lauter simulator to do the above calculations. To use it, you should download a copy to your computer as either an Excel or LibreOffice spreasheet.

Brew on

 

[Bobby_M]

Call it $2

 

[Willy]

Awesome! Thanks @Bobby_M , @mac_1103 and @doug293cz - $2.
I am totally rethinking the need to sparge. Whoa.

 

[k-daddy]

Sparging of any variety is a guaranteed boost in efficiency. Since my kettle can handle the full volume and I'm not burdened by the need for shoestring budget, I just stick with the lower efficiency for simplicity and ease of cleanup.

I'm curious Bobby... what is your full volume, no sparge BH efficiency?

 

[delium55]

Ok, I ran a simulation with the following inputs:

Target OG : 1.060​

Target post-boil volume : 5.5 gal​

Weighted average grain potential : 37 pts/lb​

Conversion efficiency : 95%​

Total boil-off : 1.0 gal​

Grain absorption rate : 0.08 gal/lb in l/kg​

For an optimal single batch/dunk sparge the grain required is 10.85 lb, and the mash efficiency is 85.8%

For a full volume, no-sparge mash the grain required is 12.31 lb, and the mash efficiency is 75.6%

If we change the target OG to 1.040, then:

For an optimal single batch/dunk sparge the grain required is 6.85 lb, and the mash efficiency is 90.3%

For a full volume, no-sparge mash the grain required is 7.54 lb, and the mash efficiency is 82.1%

I used my mash and lauter simulator to do the above calculations. To use it, you should download a copy to your computer as either an Excel or LibreOffice spreasheet.

Brew on

Good morning Doug293cz,

How can i convert this in metric?

Weighted average grain potential : 37 pts/lb in pts/kg/l
Grain absorption rate : 0.08 gal/lb in l/kg

thank in advance

 

[mac_1103]

How can i convert this in metric?

Just use standard unit conversions. Note that "pts" is gravity points (not pints).
37 pts/lb = 37 pts/2.205 kg = 81.6 pts/kg
0.08 gal/lb = 0.303 L/2.205 kg = 0.14 L/kg

 

[delium55]

Just use standard unit conversions. Note that "pts" is gravity points (not pints).
37 pts/lb = 37 pts/2.205 kg = 81.6 pts/kg
0.08 gal/lb = 0.303 L/2.205 kg = 0.14 L/kg

Thank you very much.

 

[Bobby_M]

I'm curious Bobby... what is your full volume, no sparge BH efficiency?

Assuming a low to moderate hopping rate, it lands around 65%. It could be as high as 70-75 as long as you leave nothing in the kettle but I leave a lot of wort behind.

 

[sibelman]

I leave a lot of wort behind.

I'm assuming this is largely a decision to avoid moving undesirable stuff (hops) to the fermenter. Or is it something else?

 

[doug293cz]

Good morning Doug293cz,

How can i convert this in metric?

Weighted average grain potential : 37 pts/lb in pts/kg/l
Grain absorption rate : 0.08 gal/lb in l/kg

thank in advance

Just use standard unit conversions. Note that "pts" is gravity points (not pints).
37 pts/lb = 37 pts/2.205 kg = 81.6 pts/kg
0.08 gal/lb = 0.303 L/2.205 kg = 0.14 L/kg

It's not a simple as @mac_1103 has shown. Imperial gravity points are defined as the SG that would result from 1 lb of the fermentable in 1 gal of wort (not 1 pound of fermentable mixed with 1 gal of water, subtle difference since the fermentable contributes to the volume of wort in addition to the water volume.) This way when you multiply the grain weight in pounds by the pts/lb you get total gravity points, and then when you divide by the gallons of wort you get points per gallon. Then SG is 1 + pts/gal / 1000.

We need to have the same situation for metric points when grain is in kg and volume is in L. One kilogram of fermentable in 1 liter of wort is kind of an absurdity, but that's something we just have to ignore. The proper conversion is:

37 pts/lb = 37 * 3.78541 L/gal * 2.20462 lb/kg = 308.3 pts(metric)/kg​

​

Thus the conversion constant is:​

​

3.78541 * 2.20462 = 8.3454 pts(metric)/pts(imp)​

​

Let's run a sanity check on the above. If we make one gal of wort from 1 lb of fermentable and have an SG of 1.037, then the potential of the fermentable is 37 pts(imp)/lb.

1 gal of wort = 3.78541 L of wort​

1 lb of fermentable = 0.4536 kg of fermentable​

308.3 pts(metric)/kg * 0.4536 kg = 139.84488 pts(metric)​

139.84488 pts(metric) / 3.78541 L = 37 pts(metric)/L​

SG = 1 + 37 / 1000 = 1.037​

​

Now let's turn to grain absorption:

​

0.08 gal/lb * 3.78541 L/gal * 2.20462 lb/kg = 0.6676 L/kg​

​

You should measure the apparent grain absorption for your process. The formula for this is fairly simple:

Apparent Grain absorption rate = (Total brewing water volume - Pre-boil volume) / Total grain weight​

​

Volumes should be temperature adjusted to 20°C (68°F). Since the calculation involves the subtraction of two nearly equal numbers, the accuracy of the volume measurements is critical to getting a useful result.

In case you looked at my spreadsheet, you may not have noticed that you can switch it to use metric units by using the drop-down selection in cell B2. You must download a copy to Excel or LibreOffice in order for this to work.

Brew on

 

[Willy]

It's not a simple as @mac_1103 has shown. Imperial gravity points are defined as the SG that would result from 1 lb of the fermentable in 1 gal of wort (not 1 pound of fermentable mixed with 1 gal of water, subtle difference since the fermentable contributes to the volume of wort in addition to the water volume.) This way when you multiply the grain weight in pounds by the pts/lb you get total gravity points, and then when you divide by the gallons of wort you get points per gallon. Then SG is 1 + pts/gal / 1000.

We need to have the same situation for metric points when grain is in kg and volume is in L. One kilogram of fermentable in 1 liter of wort is kind of an absurdity, but that's something we just have to ignore. The proper conversion is:

37 pts/lb = 37 * 3.78541 L/gal * 2.20462 lb/kg = 308.3 pts(metric)/kg​

​

Thus the conversion constant is:​

​

3.78541 * 2.20462 = 8.3454 pts(metric)/pts(imp)​

​

Let's run a sanity check on the above. If we make one gal of wort from 1 lb of fermentable and have an SG of 1.037, then the potential of the fermentable is 37 pts(imp)/lb.

1 gal of wort = 3.78541 L of wort​

1 lb of fermentable = 0.4536 kg of fermentable​

308.3 pts(metric)/kg * 0.4536 kg = 139.84488 pts(metric)​

139.84488 pts(metric) / 3.78541 L = 37 pts(metric)/L​

SG = 1 + 37 / 1000 = 1.037​

​

Now let's turn to grain absorption:

​

0.08 gal/lb * 3.78541 L/gal * 2.20462 lb/kg = 0.6676 L/kg​

​

You should measure the apparent grain absorption for your process. The formula for this is fairly simple:

Apparent Grain absorption rate = (Total brewing water volume - Pre-boil volume) / Total grain weight​

​

Volumes should be temperature adjusted to 20°C (68°F). Since the calculation involves the subtraction of two nearly equal numbers, the accuracy of the volume measurements is critical to getting a useful result.

In case you looked at my spreadsheet, you may not have noticed that you can switch it to use metric units by using the drop-down selection in cell B2. You must download a copy to Excel or LibreOffice in order for this to work.

Brew on

I time travelled to college - professor James Bonk chemistry/physics lectures. My brain hurts a little but that was cured by a cold beer. No worries.

 

[delium55]

It's not a simple as @mac_1103 has shown. Imperial gravity points are defined as the SG that would result from 1 lb of the fermentable in 1 gal of wort (not 1 pound of fermentable mixed with 1 gal of water, subtle difference since the fermentable contributes to the volume of wort in addition to the water volume.) This way when you multiply the grain weight in pounds by the pts/lb you get total gravity points, and then when you divide by the gallons of wort you get points per gallon. Then SG is 1 + pts/gal / 1000.

We need to have the same situation for metric points when grain is in kg and volume is in L. One kilogram of fermentable in 1 liter of wort is kind of an absurdity, but that's something we just have to ignore. The proper conversion is:

37 pts/lb = 37 * 3.78541 L/gal * 2.20462 lb/kg = 308.3 pts(metric)/kg​

​

Thus the conversion constant is:​

​

3.78541 * 2.20462 = 8.3454 pts(metric)/pts(imp)​

​

Let's run a sanity check on the above. If we make one gal of wort from 1 lb of fermentable and have an SG of 1.037, then the potential of the fermentable is 37 pts(imp)/lb.

1 gal of wort = 3.78541 L of wort​

1 lb of fermentable = 0.4536 kg of fermentable​

308.3 pts(metric)/kg * 0.4536 kg = 139.84488 pts(metric)​

139.84488 pts(metric) / 3.78541 L = 37 pts(metric)/L​

SG = 1 + 37 / 1000 = 1.037​

​

Now let's turn to grain absorption:

​

0.08 gal/lb * 3.78541 L/gal * 2.20462 lb/kg = 0.6676 L/kg​

​

You should measure the apparent grain absorption for your process. The formula for this is fairly simple:

Apparent Grain absorption rate = (Total brewing water volume - Pre-boil volume) / Total grain weight​

​

Volumes should be temperature adjusted to 20°C (68°F). Since the calculation involves the subtraction of two nearly equal numbers, the accuracy of the volume measurements is critical to getting a useful result.

In case you looked at my spreadsheet, you may not have noticed that you can switch it to use metric units by using the drop-down selection in cell B2. You must download a copy to Excel or LibreOffice in order for this to work.

Brew on

Thank you very much Doug293cz for this complete explanation.

 

[Bobby_M]

I'm assuming this is largely a decision to avoid moving undesirable stuff (hops) to the fermenter. Or is it something else?

That's correct. I generally don't like fighting for every drop of beer that makes it into the serving keg. The brew day and subsequent tasks all the way to drinking the beer is time consuming so I don't really want to come up short. I don't squeeze the bag too much so I lose some mash efficiency there. I don't struggle for volume going into fermenter so I cut it off when I have as much as I can ferment. I fill the keg to the top and discard whatever is left.

The avoidance of the kettle trub is just a blind acceptance of the theory that it can negatively impact the flavor and/or cellaring stability of the beer. I'm in the middle of a split batch Cream Ale that I hope sheds some light on this.

 

[sibelman]

avoidance of the kettle trub

One less, er, theoretical reason would be to reduce clogging risk in subsequent transfer.

But that's never happened to me, notwithstanding that many batches have included boatloads of hop bits, much of which gets thrown above the krausen line, and the rest of which sinks below the level of my diptube.

So, perhaps not a serious worry.

 

[Willy]

Did my first brew yesterday with a 15-16 g Wilser bag (bought it from @Bobby_M ) and really liked it. The batch was about 24-25 lb of grain in a Brewzilla 35 L with extension collar. Very clean looking beer!!! And it's already fermenting away - ready in 13 days.

 

[Halfakneecap]

Interesting thread. I started brewing when everyone used coolers and homemade slotted copper pipes ( SS braid if you were fancy ). Then came the fancy homemade controlled 3V with temp probes and pumps etc. I was still using the cooler then.

One club brewday i watched the host fussing and troubleshooting the fancy controlled 3V, while another member put a huge pot onto a burner and lit the gas. For the next few hours i watched one brewer fussing and fixing all sorts of problems while the other brewer had a great time, drank beers and paid hardly any attention to his pot and bag. Sold me on BIAB. I now have a robo. Love it. Until i got the malt pipe extension i'd use the bag to do double batches. Still have the bag just because