Double Mashing - working around the limitations of your brewing system

[PalCabral]

Maybe I am knocking on open doors here, but if you are limited by the size or features of your brewing system, let me give you some advise how you can work around it using Double Mashing.

Brewing systems like Grainfather, Brewzilla, Digiboil, Brewtools, Braumeister, etc, are all using malt pipes/grain baskets to contain the grains during the automated mashing. They all build around similar concepts where the brewing system circulates the wort through the malt bed at programmable temperatures. The volumes of the malt pipes/baskets are dimensioned for the size of the brewing system (20L/30L/50L etc) and this caps the amount of grains we can use in one batch. In my case, I have a 15 year old Braumeister 20L and the max amount of grains held in its’ malt pipe is 6kgs.

The Challenge

The BM 20 uses a malt pipe that is dimensioned for max 6 kilos. I have pushed it to 7kgs in the past but that was using only barley malts. If I want to make something using flaked corn, rye or wheat, or even rye malt or wheat malt, there is a fair chance the pump won’t be able to push the mash through the malt pipe if it’s stoked over full.

That poses a problem if I want to make 25L mash at SG’s above 1.060 for above +6.5% abv fermentations. In my particular case, I want to make 25L mash with an SG at around 1.075. 25L mashes at +7% ABV are perfect for me as they will enable me to do three stripping runs and a spirit run, making enough product to make it worth it. However, this will require me to masmash +8kgs of malt and grains.

When I am making high gravity beers with my BM, I just brew less volume. 18L batches instead of 25L allows me to brew +1.080 ales, no problem. But when the mash is going to be distilled, I need bigger volumes. The minimum is really 24-25L. This is the challenge.

The Solution – Double Mashing

Double Mashing means that you mash two batches of malt using the same wort. Basically, I am doubling the creation of fermentable sugars in the wort.

I start with calculating the amount of grains I will need to reach my expected SG. Granted it’s not above 12kgs, my BM’s max is 6kgs remember, I will divide the grains into two batches. I mash once, sparge, dump the spent grains and cool the wort down to mash-in temperature. Then I do the mashing again, with the second batch of grains. The double mashing doubles the fermentable sugars and I can reach my desired SG.

Modus Operandi on the Braumeister 20

In my recipe I was aiming for 25L wort at 1.077. The total amount of grains was 8.20kgs. Please note: my recipe does not have any raw uncooked grains, only malt or flaked grains. This is important.

So I split the grain bill into two batches, filled the BM with 23L water, and started a three step mashing program with batch number 1.
- Mash-in at 40C.
- Beta-Glucanase rest at 43C for 10 mins
- Protein rest at 50C for 10 mins
- and a Saccharification rest at 67C for 90 minutes.

At the end of the saccharification rest, I checked the gravity and did an iodine test. Satisfied with the conversion and SG, I aborted the brewing program and lifted the malt pipe to its’ sparging position, and I sparged the malt bed with 3L of cool water before lifting the malt pipe out. Then I cooled the wort down to 40C with the immersion chiller.

Now, 4 hours into my brewday, I emptied the malt pipe from all the spent malt and installed it in the BM for a second time. I started the same brewing program I had used in the first mashing and when it prompted me for mash-in, I filled the malt pipe with batch two. Rinse and repeat. After the end of the Saccharification rest number 2, I again checked conversion and SG. Happy with the results, I sparged with 5L of cool water before lifting the malt pipe out.

This time I let the wort cool down by itself. At 60C I mixed in 12gr of Glucoamylase to help converting the starch to sugars. I didn’t bother about Alpha amylase enzyme as I had enough distiller’s barley malt to provide the alpha enzymes during the saccharification rest.
I ended up with 24.5L wort with an FG of 1.070, a little less than I had planned for but I am still very pleased with the brewday.

Results and conclusion

Double Mashing works. It’s a fully feasible way for you to work around the limitations of your brewing system’s malt pipe/grain basket size. However, the process makes for a longer brewday than normal. For me it was 8 hours in total. But I have a volume that I can ferment and strip, using my friend the Braumeister 20.

I made some learnings. My recipe called for 60% torrefied flaked corn and I underestimated how much wort it would absorb. In hindsight, I should have filled the BM with 25L from the beginning, instead of the 23L I started with. I also realize I should have used much more sparging water. I sparged out a lot of sugars from the malt bed, I could probably extracted even more.

The other learning was the time it takes to naturally cool the wort after mash down to pitching temperature. I have always cooled the wort immediately after finished mashing. In hindsight, I should have let it cool for an hour or so, giving the Glucoamylase some quality time in the wort at 60C, then brought it down to 30C with the immersion chiller. Or I should have mashed later in the day so the wort could have cooled down over night. The waiting for the wort to reach pitching temperature literally took ages.

Q & A

- Why are you using a brewing system when you’re making grain spirits?

Many homebrewers have joined the ranks of home distillers in the last years. Maybe to add complexity to the hobby, maybe to fulfill a life-long dream to make Whiskey. Some have purchased expensive brewing systems and learned how to master them brewing beer. If I have a brewing system, and a recipe that calls for grains, why shouldn’t I use it? Especially if I know how to make a good wort with it?

- 25L / 6 gallons is a very small batch for making spirits, why aren’t you making bigger batches?

25L is a very practical size. The 30L fermentation buckets are easy to work with when full of mash, easy to clean and sanitize. You don’t need as much room as you do when you brew bigger batches. It allows me to do stripping runs with enough head space in the boiler to reduce the risk for puking. If I were making bigger batches, I would probably only use 30L buckets anyway.

But maybe most importantly, it’s the size of my Braumeister. When I bought it, I was almost buying the 50L, but my LHBS guy talked me out of it. If you’re brewing alone, you will not be able to lift out the mash pipe of the BM 50, unless you have a hoist. Knowing well I cannot count on my better half for brewing matters, and I don’t brew in a club or with a pal, I chose the smaller size. 25L batches are more than adequate for brewing beers, but I agree it’s not optimal for making Whiskey. But it is what it is. I will have to do three 8 hour Double Mashing brewdays instead. Easter is coming up and I will have a few free days.

- Do you recommend home distillers to use brewing systems for making grain spirits?

Yes. However, you need to pick the right recipe to do so. These systems are made for mashing malts, they are not suited for uncooked/raw grains. If you use flaked grains, you can get around it as long as you have enough malt and rice hulls in the bill to loosen up the malt bed. In my example above, I used 60% (2.5kgs) flaked corn in each mash but I also only filled the malt pipe to 70% (4.2kgs out of 6kgs) of capacity. I am not sure how much more flaked corn my Braumeister’s pump would have been able to cope with, TBH.

If you are using unmalted grains, such as cracked corn or unmalted rye, oats, wheat, in your mashes I would not recommend using a brewing system. These systems are not at all suited for cooking and gelatinizing grains. However, if you’re going to make a Scottish or American Single Malt Whiskey, or if you are fine with using flaked grains, hell yes.

But if you are going to buy a brewing system, it's really only going to be worth it if you are also planning on brewing beer. This is what these systems are tailored for and good at. If you are only going to be make grain spirits, I believe you'll be putting up a lot of money for not enough return, TBH.

[bilgriss]

Interesting, and a fun experiment as a proof of concept.

My own personal perspective took me down a different path. I have been a home brewer for many years, and I've had the opportunity to brew using a quite a number of different systems, equipment, and with quite a number of different people who have quite different approaches. My conclusion after a few decades is that although they each did things very differently with different hardware, the ones who had a feel for the process and learned from experience consistently made excellent beer. I've settled into some very low-tech methods, and have never been able to justify buying an expensive brewing system. So for me, brewing a bigger batch just means getting a larger mash tun and fermenting vessel, rather than changing my approach or doubling up on a procedure.

[PalCabral]

As you say, a different route, where you are not dependent on a tool or a system. For me it was a choice of convenience. I didn't want insulate a picknick box, have a false bottom, install. I was too lazy. I was an independent contractor then and could use some of the money I was making to buy gear for my hobby. And I believe it made me and my brewing a whole lot more efficient. That said, if I had to mash without the BM I would, it would just take longer time and be a whole lot more messy

[PalCabral]

Modus Operandi on the Braumeister 20

In my recipe I was aiming for 25L wort at 1.077. The total amount of grains was 8.20kgs. Please note: my recipe does not have any raw uncooked grains, only malt or flaked grains. This is important.

So I split the grain bill into two batches, filled the BM with 23L water, and started a three step mashing program with batch number 1.
- Mash-in at 40C.
- Beta-Glucanase rest at 43C for 10 mins
- Protein rest at 50C for 10 mins
- and a Saccharification rest at 67C for 90 minutes.

At the end of the saccharification rest, I checked the gravity and did an iodine test. Satisfied with the conversion and SG, I aborted the brewing program and lifted the malt pipe to its’ sparging position, and I sparged the malt bed with 3L of cool water before lifting the malt pipe out. Then I cooled the wort down to 40C with the immersion chiller.

Now, 4 hours into my brewday, I emptied the malt pipe from all the spent malt and installed it in the BM for a second time. I started the same brewing program I had used in the first mashing and when it prompted me for mash-in, I filled the malt pipe with batch two. Rinse and repeat. After the end of the Saccharification rest number 2, I again checked conversion and SG. Happy with the results, I sparged with 5L of cool water before lifting the malt pipe out.

This time I let the wort cool down by itself. At 60C I mixed in 12gr of Glucoamylase to help converting the starch to sugars. I didn’t bother about Alpha amylase enzyme as I had enough distiller’s barley malt to provide the alpha enzymes during the saccharification rest.
I ended up with 24.5L wort with an FG of 1.070, a little less than I had planned for but I am still very pleased with the brewday.

Results and conclusion

Double Mashing works. It’s a fully feasible way for you to work around the limitations of your brewing system’s malt pipe/grain basket size. However, the process makes for a longer brewday than normal. For me it was 8 hours in total. But I have a volume that I can ferment and strip, using my friend the Braumeister 20.

One more addition I would like to make. My efficiency in the BM20 is normally 75-80%, but when double-mashing it drops to 65%. I noticed that the second mashing achieved lower yields than the first. It seems the sugary wort from the first mash is less prone to convert sugar in mash number two. So you need to adapt your recipe to the lower efficiency.

I am also now able to do the double mashing end to end in 6 hours.

[Homebrewer11777]

I'm also a homebrewer who got into this hobby after year's of beer brewing. I have custom 20 gallon recirculating mashing system that works great for beer and would be fine for single malt distillers beer however my goal is bourbon and it is pretty much useless for corn based mash (using either cracked corn or cornmeal). Instead I am using my 30 gallon brew kettle for mashing and then scooping the mash into 32 gallon trash can for fermenting and fermenting on the grain.

I have a couple comments on your process.
- Why are you aiming for such high gravity wort? You mention 1.060 is doable and will I expect it would ferment cleaner than a 1.075 or 1.080 wort. With a bit of glycoamylase you will ferment down to below 1.000 and will have ABV at about 8%.
- Double mashing the way you described will be inherently lower efficiency than single mashing due to wort gravity impact on lautering efficiency. If you really want to go that route plan to use extra sparge water (perhaps a lot extra) for the second mash.
- Finally have you tried fermenting on the grain? For high corn mash it really seems to be a lot easier to separate the solids after fermentation. I am happy with a mop bucket but can imagine you could use the basket on the BM for this step with only modest loss compared to squeezing.

[howie]

the amount of water you use (23L) with 4.1kg of grain, it's almost like a BIAB method.
you are not leaving much room to sparge efficiently through a malt pipe?
also, sparge water is usually at 77C, maybe using cool sparge water is leaving sugars behind?

i have used a combination of the false bottom and a BIAB bag (instead of the malt pipe) to good effect with corn.

i don't know if there's any disadvantage or advantage that the 2nd mash is in 'sweet' water?

timewise, i'm sure about the 90 minute mash, i would probably only do 60 minutes.
2 x traditional mashes in my brewzilla wouldn't take me much longer than your method, if i did that, i would have hot strike water ready in my other digiboil for the 2nd mash.
one obvious difference is that you would have 1 x ferments @ 1.070ish, i would have 2 x ferments @ 1.035ish.
i have plenty of room in my fermenting fridges.

so in conclusion, i don't see much wrong with your method but i don't see any great advantages either.
maybe consider using a BIAB instead of the malt pipe and using hot sparge water?

[PalCabral]

I'm also a homebrewer who got into this hobby after year's of beer brewing. I have custom 20 gallon recirculating mashing system that works great for beer and would be fine for single malt distillers beer however my goal is bourbon and it is pretty much useless for corn based mash (using either cracked corn or cornmeal). Instead I am using my 30 gallon brew kettle for mashing and then scooping the mash into 32 gallon trash can for fermenting and fermenting on the grain.

Have you tried to use flaked maize/corn? It’s more expensive than cracked corn but I can use it in my BM20.

I have a couple comments on your process.
- Why are you aiming for such high gravity wort? You mention 1.060 is doable and will I expect it would ferment cleaner than a 1.075 or 1.080 wort. With a bit of glycoamylase you will ferment down to below 1.000 and will have ABV at about 8%.
- Double mashing the way you described will be inherently lower efficiency than single mashing due to wort gravity impact on lautering efficiency. If you really want to go that route plan to use extra sparge water (perhaps a lot extra) for the second mash.
- Finally have you tried fermenting on the grain? For high corn mash it really seems to be a lot easier to separate the solids after fermentation. I am happy with a mop bucket but can imagine you could use the basket on the BM for this step with only modest loss compared to squeezing.

Good questions.
1. Landing at 9-10% works great in my process. It gives me 8L low wines at 29% and a final product of 3,5-4,5L hearts. Cut. But I am re-assessing it. 1.060 will be hard to reach, I have realized. The malt pipe will too loaded and my 15 year old BM pump will have difficulties pushing the wort up throught mslt bed. When I have analyzed it I think need to use less malt, which means I only could reach 1.055 actually.

I am using Glucoamylase in the cool down phase and my ferments regularly go totally dry, 1.000. No need for alfa amylase though.

2. Yes the efficiency is lower. I have added more grains and I need about 4-5L sparge water per mash, so toally 8-9L.

3. I will not ferment on grain! It will destroy my manicure No, seriously, I’m not venturing there, for me it’s a no go zone fill of aversion, I prefer a clean ferment. But I am waiting for a block of YLAY to arrive so I will have to eff my manicure sooner or later.

Overall, I did this to prove that I can use my old brewing system and I can. It’s practical and I make use of the investment I made back in the days. Is it 100% efficient? No. But it’s practical.

[PalCabral]

the amount of water you use (23L) with 4.1kg of grain, it's almost like a BIAB method.
you are not leaving much room to sparge efficiently through a malt pipe?
also, sparge water is usually at 77C, maybe using cool sparge water is leaving sugars behind?

i have used a combination of the false bottom and a BIAB bag (instead of the malt pipe) to good effect with corn.

i don't know if there's any disadvantage or advantage that the 2nd mash is in 'sweet' water?

timewise, i'm sure about the 90 minute mash, i would probably only do 60 minutes.
2 x traditional mashes in my brewzilla wouldn't take me much longer than your method, if i did that, i would have hot strike water ready in my other digiboil for the 2nd mash.
one obvious difference is that you would have 1 x ferments @ 1.070ish, i would have 2 x ferments @ 1.035ish.
i have plenty of room in my fermenting fridges.

so in conclusion, i don't see much wrong with your method but i don't see any great advantages either.
maybe consider using a BIAB instead of the malt pipe and using hot sparge water?

You are right about starting volume and sparging volume. In the last batches I have upped both. In total I use minimum 8L sparge water. But I think that you will find that the need for 77C sparge water has been proven wrong. Cold water works just as well to rinse the maltbed. Here's an article about it: https://brulosophy.com/2016/04/11/sparg ... t-results/

The malt pipe concept is pretty similar to BIAB. I used to brew that way before I got the BM. I like BIAB but I would feel it was a step back, in a way. I know it’s a silly thought but I prefer the BM.

In the last two batches I have checked the conversion after 60 minutes, because I too was thinking 60 mins should be sufficient. It turned out that I am fully converted after 60 mins after the first mash but not after 60 mins in the second batch. In fact, in my last run, I mashed for 100 minutes before I got full conversion. The effiency is much poorer the sweeter the wort gets.

[PalCabral]

- Finally have you tried fermenting on the grain? For high corn mash it really seems to be a lot easier to separate the solids after fermentation. I am happy with a mop bucket but can imagine you could use the basket on the BM for this step with only modest loss compared to squeezing.

so in conclusion, i don't see much wrong with your method but i don't see any great advantages either.
maybe consider using a BIAB instead of the malt pipe and using hot sparge water?

I did this project to prove that I can use my brewing system to make all grain spirits. I never said it was more efficient, nor better (very subjective term), but it is a fully viable alternative making Bourbon, without having to stand with a shovel in your hands over boiling water stirring the life out of gelatinizing cracked corn or cement-like rye flour in a 60-100L bucket. The whole point of using a brewing system is to not have to spend hours separating wort from solids.

Advantages, besides not having to deal with gelatinizing, cooking, stirring, wringing, and scooping, is that I can ferment off grain. To me this is a blessing and I believe (subjectively) it makes a better, crisper, wash that will show up positively in the taste of the spirit. It gives the yeast a better environment to do it's thing. And less muck to clean up after. The yeast cake is waiting for me and the next ferment. For me personally, it's an advantage that I can make use of an investment I made 15 years ago. I would not recommend someone buying a brewing system just to make whiskey but if you already have one from your brewing days, I have shown it can be used.

Disadvantages are the higher costs using malted and flaked grains as opposed to animal feed. I'm not sure the lower efficiency when double mashing is a big disadvantage, because I'm not sure how efficient the alternative is. I am pretty sure there are losses in the alcohol that cant be wringed out of the solids after fermentation too. For me the smaller size is not a disadvantage but if you're making all your ferments at once in a big batch, a brewing system will be impractical, at least a small one like mine.

Have a great brewing Sunday.

[Saltbush Bill]

The proof of the pudding will be if your still using the same equipment and method a year from now.....I suspect not.

[PalCabral]

The proof of the pudding will be if your still using the same equipment and method a year from now.....I suspect not.

If my crystal ball was working, I would have won the Eurolotto years ago and I'd be on a sunny beach somewhere drinking drinks with a silly grin on my face. If your's had worked too, maybe we'd be sitting next to eachother, even? But without our crystal balls fully functioning, Bill, only time will tell.

[howie]

crystal balls apart, i've done a few experiments with my 35L BZ.
one was putting the corn straight into the BZ with stirrer at the ready.
despite vigorous stirring, the corn settled on the bottom, covering the temp sensor and causing a thermal overload
i was quite successful with 100% feed corn in a BIAB sitting on the false bottom with the recirc arm going.
i used some alpha liquid enzyme to keep the mash thin while i gelantised it, with no stirring required.
then more lquid enzymes at a lower temp.
i did a 60% rye in the BIAB/false bottom method.
despite a beta glucan rest, i still got a little bit of glup that required 2 stirs only.
i think i did both BIABs with about 25L of water so it requires no sparging.
i have a pulley above the boiler to lift and drain the BIAB.
it's just an option i use sometimes for lots of mash water without the constraints of the malt pipe in the BZ.

[PalCabral]

crystal balls apart, i've done a few experiments with my 35L BZ.
one was putting the corn straight into the BZ with stirrer at the ready.
despite vigorous stirring, the corn settled on the bottom, covering the temp sensor and causing a thermal overload
i was quite successful with 100% feed corn in a BIAB sitting on the false bottom with the recirc arm going.
i used some alpha liquid enzyme to keep the mash thin while i gelantised it, with no stirring required.
then more lquid enzymes at a lower temp.
i did a 60% rye in the BIAB/false bottom method.
despite a beta glucan rest, i still got a little bit of glup that required 2 stirs only.
i think i did both BIABs with about 25L of water so it requires no sparging.
i have a pulley above the boiler to lift and drain the BIAB.
it's just an option i use sometimes for lots of mash water without the constraints of the malt pipe in the BZ.

I like BIAB, don't get me wrong. It's how I started, but small scale, small bag too

60% rye is out of question with the BM, the pump wouldn't handle it. I plan to make a Penn style Rye this summer, 70% rye, maybe I try the BIAB method but the weight thing is worrying. I can't depend on my wife and my son just moved out. And if I spend money on a hoist, there will be words mentioned, harsh words. I was planning to bite the bullet and go with YLAY for the Rye whiskey, so Í won't be able to duck fermenting on the grain forever.

When I have done my double mashes up to now, I've been below 5kg is the mash tun per turn, and I haven't had problems with the pump not being able to push the wort through the malt pipe. But today I brewed a Kentucky Common beer, just normal single mashing, no funny business, but with 5 1/2kg of grains, and the pump was having difficulties. The recipe contained torrefied maize but only 1kg, still the pump was having to work hard today - a lot of "pump interruptions", as it's called in BM lingo. I didn't use rice hulls, which I normally do with flaked grains, so maybe if I had it wouldn't have been so hard for the BM. It's possible to work around the limitations but there are still limitations to work around.

[howie]

it depends on your brewing place situation obviously, but if you can attach something above boiler, just a couple of cheap pulleys and suitable rope will do the trick.
i also use the BIAB & pulleys when i ferment on the grain, the BIAB goes in the boiler to strain the ferment and ready for a stripping run.
does your BM have a false bottom?

[MooseMan]

I also use bags and pulley to strain YLAY ferments very easily.
Ferment on grain, then line a secondary vessel with a BIAB and fill. Hoist up over the vessel, a couple of wraps with elastic strap to compress the bag and leave overnight.

[PalCabral]

it depends on your brewing place situation obviously, but if you can attach something above boiler, just a couple of cheap pulleys and suitable rope will do the trick.
i also use the BIAB & pulleys when i ferment on the grain, the BIAB goes in the boiler to strain the ferment and ready for a stripping run.
does your BM have a false bottom?

In the BM it's the malt pipe that has the false bottom. You snug in the malt pipe when the water is ready for mash in, then put in the perforated bottom plate and then a SS mesh plate on top of it. When these two "false bottoms" are in place, you fill the malt pipe with your grains. Then you top the malt in the malt pipe with yet another mesh plate and performated plate, so you have "false tops" as well.

The BM pumps wort from the bottom up through the plates and through the malt inside the malt pipe and out the other end, creating circulation through-out the mashing process. In the BM20 I can fill 6kgs of malt, I've done 7, in the malt pipe but at some point the pump won't be able to circulate the wort, and then you're stuck. When using flaked grains or other unmalted grains, the gluey consistency of the grains will put additional limits of how much grains one can use. It's made for malt, basically, and maybe 10-20% of unmalted adjuncts, so when I am using up to 60% flaked maize I cannot fill the malt pipe to capacity. It's not ideal, I know.

I also use bags and pulley to strain YLAY ferments very easily.
Ferment on grain, then line a secondary vessel with a BIAB and fill. Hoist up over the vessel, a couple of wraps with elastic strap to compress the bag and leave overnight.

I guess this is the way I would have to do it if I wanted to scale up volume. Let's see if Bill's old crystal ball is working or not.

[Saltbush Bill]

My crystal ball shows pullies and ropes and wet dripping bags.

[MooseMan]

My crystal ball shows pullies and ropes and wet dripping bags.

I don't have one sadly Bill, but my gut instinct seems to agree with your ball!

PalCabral I still have my 40L BIABIAC setup, with a big square cooler modded for sparging, 2x50L stainless kettles with sight glass, thermos etc.
Not been used since I brewed my last IPA...