Small Batch Boil-Off & Its Affect on Ion Concentration

I brew 2.5 gallon BIAB batches. In an average batch, here are the water volumes I work with:

90-Minute Boil
Strike Water ≈5.3gal
Starting Boil Volume ≈4.6gal
Ending Boil Volume ≈3.1gal

60-Minute Boil
Strike Water ≈4.8gal
Starting Boil Volume ≈4.1gal
Ending Boil Volume ≈3.1gal

For my water calculations I use Bru'n Water. I put my total water volume in the Mash Water Volume cell. I don't put anything in the Sparge Water Volume cell. I then make my adjustments from there.

My concern though is that when I factor my boil-off (≈1gal per hour), there is quite a bit of concentration of the minerals, lactic acid additions, etc. Even factoring grain absorption and the amount of minerals/acid/etc. carried away in the grain, there is a concentration.

I realize in all brewing there is a concentration of minerals. But with smaller batches, while the amount boiled off might be the same (≈1gal per hour) the percentage of the total volume boiled off is higher meaning more minerals left behind. In my average batch, my boil-off percentage is ≈33%.

For a batch of Dortmunder Export with a 90-minute boil, my adjusted water profile is:

Profiles (ppm)
Ca 54
Mg 8
Na 23
SO4 76
Cl 58

BUT...if I put the calculated amount of minerals & acid in the mash to create that profile at the start of the boil, I end up with the following ppm concentrations in the wort at the end of the boil:

Ca 80.72
Mg 11.84
Na 34.04
SO4 112.48
Cl 85.84

This is figuring some of the minerals and water will be absorbed by the grain. To get this figure, I divided by starting boil volume (4.6gal) by my ending boil volume (3.1gal) to get 1.48. Then I multiplied that number by my starting profile.

Is there something here I ought to be concerned about? I'm wondering if rather than using the actual volumes I use, if I shouldn't use some adjusted amount. Maybe a percentage? Perhaps adjust my water based on the ending kettle volume plus 10% (the average boil-off ratio)? Or something else? I don't know.

Yes, this discussion was conducted a few months ago too and a typical boil off rate for a 5 or 10 gal batch is likely to result in an excessive water loss in a small batch. If the batch volume is reduced by more than about 15 %, then you do need to be concerned about boil off rate. You may also need to consider that concentration of minerals and reduce the total mineral additions.

mabrungard said:

Yes, this discussion was conducted a few months ago too and a typical boil off rate for a 5 or 10 gal batch is likely to result in an excessive water loss in a small batch. If the batch volume is reduced by more than about 15 %, then you do need to be concerned about boil off rate. You may also need to consider that concentration of minerals and reduce the total mineral additions.

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What would your recommendation be Martin? Should I simply add minerals equivalent to a volume roughly 10-15% more than my post -boil volume?

I want to understand this and obviously know what to do for the best beer possible.

I think the implied easiest solution is to reduce your boil off rate

Mer-man said:

I think the implied easiest solution is to reduce your boil off rate

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Unfortunately, that really isn't possible apart from increasing the size of my batches. Back surgery doesn't allow that though.

And I can only adjust the flame so much. When I'm starting off with smaller volumes, if the boil-off rate in gallons is the same or similar to the boil-off rates of guys doing larger batches (5, 10, 15+) their amounts and my amounts are the same, but percentage wise they are different. 1 gallon of boil-off from a 10 gallon batch is only 10%. But one gallon of boil off from a 3 gallon batch is 33%.

Anyway, here is a helpful response from Martin via email:

"The high degree of boil off in small batches is a concern. You do have to limit the salt additions to avoid having higher than desirable concentrations in the final wort. In the 5 to 10 gal batch size range, I typically see 10 to 15% reduction in volume from boiling. You have 20 to 30% reduction and that could create problems. I've had brewers complain about highly mineralized profiles in Bru'n Water (such as the pale ale profile), saying that their beers were too minerally. I found out that they had the high boil off percentages you mention.

You should reduce your mineral additions to accommodate that elevated degree of concentration. I'll be working on an upgrade to enable users to quickly assess the effects of concentration and hopefully avoid it."

This is great! I will be working on this and looking forward to the update mentioned.

I sent Martin another email about lactic acid additions. I'm wondering, since the ion concentration is getting higher, so is the "acidity" of the beer as the boil goes on. I will check my beer pH during the next brew day after the boil to see what it is. But if anyone has input on this, I'd appreciate it.

Following.

Alternatively, have you attempted to brew indoors instead of on the propane burner? Perhaps with a smaller kettle?

I've started doing tiny batches now after I moved, smallest I've done is a .75G post boil volume with a .5G boil off rate. Talk about concentration. My hop utilization is a bit higher (not really significant enough to care about) as well as the pre boil OG is so much lower than typical.

No I haven't tried that. Don't really have the capability to. I am brewing this coming Monday. I am going to try to adjust my burner. But I'm also doing two of the same beer back-to-back. For one I'm going to do a regular 1.25qts/lb ratio of water to grist.

I'm only going to adjust that initial strike water. Then I'm going to "sparge" by adding in the rest of the water to get to my target volume. This water will be untreated with additional minerals.

I'm debating doing this with RO water in one and just filtered tap water in the other.

Thoughts?

OK. I thought I'd post the way that I'm working around this issue of boil-off and evaporation. I'm using Bru'n Water, but my method is definitely not the way it is meant to be used. I'll be waiting for the next update @mabrungard but until then, here's what I've got.

First thing I'm doing is figuring out how much water I'll be using to strike with. I mash with the full volume of water and would like to keep it that way. Once I have this number, I put my grain bill into Bru'n Water and then put my Mash Water Volume in proper cell on the Water Adjustment tab. From here, I add enough lactic acid to adjust ONLY the pH.

After that, I'm figuring out how much of that water will remain in the kettle after I pull the bag. This is simply strike water minus the amount of water absorbed by the grain. In my 90min boil batches, this is always 4.6gal.

So, I've got 4.6gal of water that will be concentrated down to 3.1gal after a 90min boil. That means that all the ions that are in my water will be concentrated by roughly 50%. I made an Excel spreadsheet that does the math for me and shows me what my concentrations will be after the boil is over.

From there, I take those concentrated numbers and I putting them in Bru'n Water. But I put these in the Water Report Input tab as if it was my water profile. This allows me to see how my concentrated water compares to the target profile. From here, I'll make the necessary mineral adjustments to get me the rest of the way.

So...here are some numbers from the batch of Dortmunder Export I'm brewing on Monday.

STARTING WATER:
IONS STARTING PROFILE
Ca 28.0
Mg 8.0
Na 23.0
SO4 54.0
Cl 28.0
HCO3 56.0

I'm mashing with 5.38gal of strike water. This water combined with the grain, will be treated with enough lactic acid (4.04mL) to bring the mash pH down to 5.4. That's all I'm doing in the mash...lactic acid for pH adjustment.

I'll mash for 60min and then pull the bag of grain. When the bag is pulled, approximately .78gal of water will be retained by the grain leaving 4.6gal in the kettle. Again, this is water that, other than lactic acid addition, is still untreated and has the ion concentration from the profile given above.

Those 4.6gal will be boiled for 90min resulting in 3.1gal of water with the following water profile:

END-OF-BOIL PROFILE:
IONS ENDING PROFILE
Ca 41.55
Mg 11.87
Na 34.13
SO4 80.13
Cl 41.55
HCO3 83.10

With that profile, I'm very close to the numbers for the Yellow Dry Profile, I'm targeting for the Dortmunder Export. To get me the rest of the way, I am adding .62 grams of Gypsum and .16grams of Calcium Chloride to pretty much spot on with the target profile. I will add this to the boil, after I've pulled the bag.

So, in a sense, I'm starting with the end of the boil and the mineral profile I'm looking for and then working backward. I'm hoping this is going to work. It makes sense in my head...but that doesn't mean it actually makes sense.

Another solution would be to top off with boiling water during the boil to target a 15% reduction/hr max. As long as a slightly larger batch would fit in the fermentor of course.

dstar26t said:

Another solution would be to top off with boiling water during the boil to target a 15% reduction/hr max. As long as a slightly larger batch would fit in the fermentor of course.

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I'll have to think about this as an option. If I went with this method, it could means that I pretty much always hit my target gravities and volumes as I'll always be boiling off more than 15%.

If I adjusted my pre-boil volume & gravity in my software figuring that I'd start the boil with 3.45gal of wort at 1.040, I could design the recipe to get that. Then, I tell it I'm going to end the boil with 3gal of wort at 1.052.

The only annoying thing is that once I hit the 3gal mark, I'd need to keep adding water in small amounts to the boil kettle. That's not a huge deal though.

Definitely something to consider. Any downsides to this suggestion?

dstar26t said:

Another solution would be to top off with boiling water during the boil to target a 15% reduction/hr max. As long as a slightly larger batch would fit in the fermentor of course.

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So I've been looking at this as a (perhaps) much simpler solution to this problem. I've been running some numbers, but I'm wondering...is there any downside to doing this?

If I went with this method, the HUGE plus is that I just modify the water like I normally would. And calculating that I'd start out with less volume, this water would be concentrated, but I'd be adding "unconcentrated" water back in that would get me to the ≈10% evaporation.

So, I'd start the boil out with 3.33 gallons of wort. I'd boil like normal losing about 1 gallon per hour. That would mean that at the end of the boil, I'd have approximately 2.33 gallons of wort. But if I pre-boiled .66 gallon of filtered water I would simply add that to the wort to get me up to my target post-boil volume (3 gallons). I would factor this into my recipe of course. I'd be "diluting" the wort back to it's target gravity.

Basically it'd be like I "over-boiled" and I'm adjusting the volume and gravity back to where it was supposed to be.

A few questions remain though.

1. Since the filtered water is totally unmodified, meaning the pH is still at ≈8.2, should I treat it with acid to match the mash water profile? i.e. If I added .5mL per gallon of mash water, should I add that same ratio of lactic acid to this water? Or should I treat it more like sparge water and just add enough acid to get it down to around 6 pH?

2. Are there any downsides to this method? Are there reactions in the boil that need to happen that with this method won't? I realize that I'll be boiling a wort that has slightly higher gravity so my hop utilization will be a bit less. This can be accounted for through testing/experimentation/adjustment/etc. But other than that, are there other issues?

3. Is there any "wrong time" to add this top-up water? I mean, I could add it at the beginning, middle, end of the boil or or even after chilling correct (as long as things are properly sanitized of course)?

My thought with adding it at the end of chilling is that by my calculations, I could chill 2.33 gallons of wort to 75F and then add pre-boiled, filtered water from my fridge at 34F and get it dropped another 10F to my targeted 65F ale pitching temp instantly.

Anyway...let me know what you think.

I do minimum 90 minute boils but don't add hops until 60 minutes. If something went unexpected in the mash or lauter (or just want the largest batch size for the kettle), that gives me 30 minutes to correct, either by extending that 30 minutes to concentrate the wort before hops are added, or by adding boiling water to dilute. What you are proposing is extreme compared to the ~0.5 - 1.0 gallon I would add to 6 - 13 gallon batches.

1. I adjust the pH pre-boil, targeting 5.45 maximum. I want this done before any hops are added to reduce harshness. You will need to experiment with that and I would expect you need to add acid to your top-up water, or over acidify the kettle prior to topping up.

2. Hop utilization is your main concern so stay consistent (and keep it simple) with your process. I don't see any other down sides.

3. I would add the water before hops are added but this is just personal preference. The less fooling around with unpitched cooled wort the better. Also, I prefer to have all the water interact with the extracted malt compounds during a boiling state. I don't have any scientific data to back this up but there are complex interactions during the boil that I don't think are fully understood and I think diluting after wouldn't be ideal. That said, I'm sure no differences could be detected in a triangle test.

Could very well be too early to tell, but I am wondering if you've come up with a solution you like, Hafmpty?

Thanks for starting this thread, this was something I'd never considered!

Cheers!

Ewow said:

...I am wondering if you've come up with a solution you like, Hafmpty?

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Thanks for checking in!

Unfortunately, like you say, I feel it's too early to tell. I did brew a Dortmunder Export and a Schwarzbier modifying the water for proper pH and FINAL ion concentration.

The only issue is that I did not get the hop bitterness I was hoping for. That could be that there wasn't enough sulfate in the water...although my numbers indicated a 110ppm concentration of sulfate in the finished beer vs. 58ppm Chloride. I've since "fixed" this by boiling some hops for 60min and making a "super-bitter water" that I added to the kegs for flavor modification. It's made them better for sure.

There is no mineral "bite" or acidity that I notice. That said...I want to do some more tests, so I'm re-brewing on 1/18 and will be doing two back-to-back batches of only the Dortmunder Export. I'm going to increase the amount of hops by about 20% and try two different water modification methods comparing the beers side-by-side once they are done fermenting.

Beer #1 I'm going to do what I proposed in post #8

Beer #2 I'm going to do what I proposed in post #11 using slightly acidified RO water for the top-up at the end of the boil.

It should be fun! What do you think? Any feedback or input?

BTW...I'm going to chronicle this on my YouTube Channel Half Empty Brewing. Check it out if you're interested.

Hey, man! Fun times!! Thanks for documenting all this.

As mentioned previously, this was something I had never thought about before. It seems like parts of my process relevant to this discussion are similar to yours (full-volume mashes, similar pre- and post-boil targets), so it was cool to see this brought up for discussion.

After reading your initial couple of posts (and searching for the other thread that Martin mentioned), here is what I was going to try for my next batch:

1. Enter grain bill as usual in Bru'n Water
2. Enter my post-boil volume target in the cell for mash water volume on the Water Adjustment tab
3. Add minerals as needed to approximate my targets
4. Change the cell for mash water volume to my actual mash water volume
5. Add acid as needed to approximate my target mash pH

I think the key difference between what I was planning to do and what you are planning to do in post #8 that you linked to is that I am starting from RO water. Does that seem right? If so, any interest in starting from RO? Seems like it could save you some trouble! Then again, once you've figured out how to calculate the effect of boiling on your tap water, doing it in the future will be easy-peasy.

I am far from an expert, but I don't currently see 'downfalls' to the two methods you outlined. That being said, I think I'd have a personal preference for what you suggested in post #8 (just sounded simpler to me). Please let us know how it goes!

I'm actually already a subscriber to your channel. Enjoying the videos, for sure!

Cheers!

Ewow said:

...here is what I was going to try for my next batch:



1. Enter grain bill as usual in Bru'n Water

2. Enter my post-boil volume target in the cell for mash water volume on the Water Adjustment tab

3. Add minerals as needed to approximate my targets

4. Change the cell for mash water volume to my actual mash water volume

5. Add acid as needed to approximate my target mash pH

Click to expand...

One more reason I love this forum. What you describe is quite a bit simpler...especially since you start with RO water. I'd like to avoid the added expense of RO water if I can avoid it...but I'm also all for better beer and an easier process (plus Wally World has Distilled water for 88 cents a gallon).



One thing to consider is the continuing affect on the pH of the lactic acid that will be "carried over" into the boil. Mineral ions will affect the pH and acid will affect the flavor. I know you know that there's an interplay.



To see what effect this would have I calculated the necessary lactic in my batch of Dortmunder using ONLY Distilled water. This meant I would need 2.78mL of Lactic Acid to get the pH down to 5.4 in 4.88 gallons of water (distilled). Of that 4.88 gallons, ≈.78 will be absorbed a removed with the grain.



That leaves ≈4.1gal of water with ≈2.34mL of Lactic Acid (≈.47mL of Lactic acid being removed by grain absorption). Once that boiled, those 2.34mL of acid are not contained in 3.1gal of water.



Once I add the minerals to get to my appropriate ion concentrations POST-BOIL, and factor the acid concentration, my pH has now dropped from 5.4 to 5.14. According to most sources, 5.1-5.2 is the proper post-boil range, so I'm still in the right range so I'm good.



BUT...if I'd added enough acid to get me to 5.2 instead of 5.4, I'd be at a 4.87pH at the end of my boil...way too low.



So...all this is to say it's something I need to be aware of regardless of the water I use...there is an interplay between the lactic acid and the mineral additions. The take-away for me is that I need make it part of my calculations to check the final pH expected at the end of the boil factoring the lactic acid carry over and the targeted ion concentrations and make sure I'm not too low.



So, I think what I'm going to do is go with the process I mentioned in post #8 and then I'm going to try your way with brew #2 and just run all distilled water modifying in the ways you proposed.



This way the only thing I'm changing is the water. Everything else will remain the same. Very cool! Thanks for watching the videos too. I'll try to remember to give you a shoutout in the next video.



FYI THIS PART IS FOR MY OWN REFERENCE SO I KNOW WHAT MY PLAN IS:



BEER #1 - Using Filtered Tap Water

1. Use the full volume of filtered tap water in the mash.

2. Adjust the full volume of mash water with Lactic Acid to drop pH to the appropriate level for the MASH.

3. Add mineral additions to the BOIL ONLY after factoring the concentration of the mineral ions from the filtered water during the boil.



BEER #2 - Using Distilled Water

1. Use the full volume of distilled water in the mash.

2. Adjust the full volume of mash water with Lactic Acid to drop pH to the appropriate level for the MASH ONLY.

3. Add mineral additions to the BOIL ONLY after factoring the concentration of the mineral ions during the boil.



In BOTH BEERS...monitor the interplay between the lactic acid additions and it's affect on the final pH once the mineral additions are added in.

Hey, man!

Excited to see how this all goes. Shout out? Sweet!

Is something wonky with step 3 for Beer #2? I am wondering if 'filtered water' was intended to say something else? Or maybe I am just confused

Just for the sake of record-keeping and in case anyone is interested, I think this may be the conversation Martin referred to earlier. I also found a discussion over on the AHA website about this as well.

Ewow said:

Hey, man!

Excited to see how this all goes. Shout out? Sweet!

Is something wonky with step 3 for Beer #2? I am wondering if 'filtered water' was intended to say something else? Or maybe I am just confused

Just for the sake of record-keeping and in case anyone is interested, I think this may be the conversation Martin referred to earlier. I also found a discussion over on the AHA website about this as well.

Click to expand...

Thanks for catching that. Edited and fixed. Also those posts are great. Thanks for posting those. Helps me to see that I'm not the only one working to figure this out. Seems like we are on the right track. AJ mentioned just testing and experimenting and adjusting to get the beer you want. Well...seems like that's what I'm shooting to do so I'm glad I'm at least sort of on the right track.

Just wanted to check in on this topic.

I've brewed about 10 batches since the last post in this thread. All 2.5gal batches using the method(s) outlined in this thread.

I use city water when I can, but many have been made with distilled water. I use phosphoric acid to adjust the pH in the mash and then add minerals to the boil kettle. The minerals amounts are calculated for the FINISHED boil volume so as not to concentrate them too much.

I have had really good feedback on the beers at club meetings. In addition I entered a couple Pilsners (German & Bohemian) into my club competition and received scores of 40 & 39 from a guy that brews A LOT of lagers. He actually asked me to brew with him to show him what I did.

If you are a small batch brewer looking to make the best beer you can, this is definitely something to try in your own brewing. Let me know your experiences.

Thanks for the update on what you've found, hafmpty. It's nice to see this thread being updated after trying a few things over multiple batches and getting feedback from others.

I haven't brewed much since the wedding and the move, but I am looking forward to getting back into this.

Cheers!

Ewow said:

Thanks for the update on what you've found, hafmpty. It's nice to see this thread being updated after trying a few things over multiple batches and getting feedback from others.

I haven't brewed much since the wedding and the move, but I am looking forward to getting back into this.

Cheers!

Click to expand...

Glad to see you're back! And you survived. That was a lot going on in a short span of time so it's not surprising you haven't had a chance to brew. But now it's time to get on it!