Mash thickness effect

[InspectorJon]

BIAB - I am planning a big imperial stout. My seven gallon kettle will not accommodate all the grain and water. If I mash at a 1 qt/lb initial rate, lift and squeeze, then batch sparge with the remaining water I need to get to boil volume will that work? What effect will such a thick mash have on efficiency/conversion?

 

[DBhomebrew]

This is exactly how I approached getting a 3.5G 1.095 barleywine out of a 5G pot. Worked quite well. The mash got pretty mud-like by the last pound or so, but still doable. Be sure to mix well, I used a big whisk. For the sparge, I dunk in a bucket. Put the full bag in, open it up, give a good mix, close it up, pull it. The longer you let the first runnings drain, the more effective the sparge will be. My barleywine got 70% efficiency into the pre-boil.

 

[doug293cz]

1 qt/lb will be a very thick mash, and may be difficult to stir adequately to break up dough balls. You should also mash longer, as according to Kai Troester, thick mashes convert more slowly.

What are your kettle volume, your pre-boil volume target, and grain bill weight?

Brew on

 

[InspectorJon]

What are your kettle volume, your pre-boil volume target, and grain bill weight?

7 Gallon Kettle, 6.25 Gallon pre-boil and 19.5 lb grain

 

[InspectorJon]

This should take care of dough balls

 

[doug293cz]

7 Gallon Kettle, 6.25 Gallon pre-boil and 19.5 lb grain

Assuming a grain absorption rate of 0.07 gal/lb (appropriate for a moderate squeeze), I get your strike water volume at 4.88 gal, and mash volume at 6.4 gal - gonna have to be careful not to slosh during dough in. Sparge water volume would be 3.0 gal. If you get 100% conversion efficiency, your mash efficiency should come out at ~80-82%, and your pre-boil SG at ~1.086.

Brew on

 

[InspectorJon]

That is pretty much what I was aiming for. I just was not sure how a 1 qt./lb mash ratio would work out. That's pretty thick. I have seen it cited in a few places that some of the British brewers mash this thick. I was thinking of mashing for an hour at 148 sliding down to 145 then batch sparging at 154 or so for another half hour to encourage conversion efficiency.

 

[doug293cz]

That is pretty much what I was aiming for. I just was not sure how a 1 qt./lb mash ratio would work out. That's pretty thick. I have seen it cited in a few places that some of the British brewers mash this thick. I was thinking of mashing for an hour at 148 sliding down to 145 then batch sparging at 154 or so for another half hour to encourage conversion efficiency.

You are better off from a mash efficiency standpoint if you get as much conversion as possible before you sparge. This will result in less sugar being retained in the grains, thus increasing lauter efficiency.

Brew on

 

[jerrylotto]

I step mash. Do a normal mash at half scale, then use the collected wort to mash the second half with an added sparge.

 

[InspectorJon]

Brewing that big bad boy today. That's a full mash kettle. Priceless BIAB calculator works again.

 

[jerrylotto]

I just realized I called the process that I was describing step mashing which is actually just an incremental temperature mashing technique. When I was trying to describe is called iterative or reiterative mashing.

 

[InspectorJon]

I went back an forth on whether to do reiterated mash or this way. I guess I ended up here with a thick initial mash and batch sparging. I kept the dark roast malt out of the first mash. I am going to mash/steep them in the sparge water, remove them and then sparge the big mash in that water. 12 lbs of two row + 4 lbs flaked oats + 1 pound of dark crystal in 5 gallons of water = very full 7 gallon kettle. I'll steep 2 lbs of various roasted malt in 2.5 gallons sparge water then sparge the rest of the grain in that.

 

[jerrylotto]

That process isn't going to convert much of the starch in the latter stages to fermentable sugars. Don't think of mashing as a flavor extraction process, it is more of an enzymatic process. What's most important is the temperatures you keep the wetted grain at and for how long.

 

[InspectorJon]

All the convertible grains are in the primary mash at 148* for 90 min. I don't believe there are any convertible starches in the roast, or so I have read. Steeping them at 140* or so for 45 minutes should get all the goodness out. At least that's the plan. We will see how it goes. It's kind of the same process as cold steeping roast rather than mashing just sped up by the warm steep.

 

[jerrylotto]

That may be the case with black patent but dark Crystal? What is it about 120L? Plenty of convertible starch in that. Of course if you steep it at 153F instead of 140F or even148F - you should get a little more of the "goodness" out.

 

[PersonalBrewer]

I'm doing 1.3 qt per lb and use a large whisk to keep things moving. And I just mash for an hour.

I just figured I would try it, and see how it did. Had no clue about conversion etc.

I am BIABasket and put some roughly 150 degree water through the basket and push a lot of the liquid out, enough to bring me up to max no boil over level.

Works for me, giving roughly 7% ABV and last batch went into the fermenter at 1.072.

I never have had any balls to break up, but always stir in and then stir frequently with the large whisk.

 

[InspectorJon]

A pound of 75L crystal malt went in the mash. .5 lb black malt 500L, .75 lb Carafa II special 425L and .75 lb roasted barley 300L were steeped and mixed into the sparged grains. First runnings 1.090, second runnings 1.068. Starting boil gravity 1.079. Very dark and roasty flavor.

 

[Noob_Brewer]

Whats your predicted OG? Are you on target thus far?

 

[InspectorJon]

Numbers looking good. Three hour boil to OG of 1.128.

 

[InspectorJon]

Just because I could, I did a second sparge with 2 gallons and got another 2 gallons of 1.035 third runnings. An hour boil on the stove in the kitchen and some hops should give me a 1.3 gallon batch into the Little Big Mouth Bubbler for a 12 pack of American Stout 5.2%. I can drink that sooner rather than next fall. I'll be documenting more about this Abraxas Emulation over here if anyone is interested.

 

[Holden Caulfield]

What effect will such a thick mash have on efficiency/conversion?

A little late, but just putting some science behind mash thickness and conversion (limit of attenuation) for future reference.

Per Braukaiser's conversion analysis, see graph below, "The results for mash thickness were somewhat surprising. Contrary to common believe no attenuation difference was seen between a thick mash (2.57 l/kg or 1.21 qt/lb) and a thin mash (5 l/kg or 2.37 qt/lb). Home brewing literature suggests that thin mashes lead to more fermentable worts, but technical brewing literature suggests that the mash concentration doesn't have much effect in well modified malts [Narziss, 2005]. Briggs cites data that doesn't show a change in fermentability when the mash thickness is changed [Briggs, 2004]. This was confirmed by these experiments where all the data points were on the same curve that had already been established in the temperature experiment. "

To summarize, mash thickness is one variable that has little impact on enzymatic conversion. That said, as mentioned by others a thinner mash does enable the mixing to be easier, especially when you get down to 1 qt/lb which is quite thick for a mash. One other benefit of thinner mashes, per Gordon Strong, is that they make it easier to get more consistent temperature throughout the mash. In addition, if you don't heat your mashtun, then loading it with more liquid will reduce the temperature loss over time.

Given this, in my opinion, no need to mash very thick unless you need space in you mashtun for many temperature steps that are being raised via boiling water. I use ~1.5 qts/lb for standard mashes and ~1.85 for decoctions. If doing a step mash, I may start as low as ~1.25 qts/lb to ensure I have enough room in my mashtun for temperature raises and sufficient sparge water available to obtain reasonable efficiency.

 

[1bottlerocket]

On our last brew this past weekend we got 72% efficiency, but we seem to get in the 70s in a thick or thin mash. We've tried a few different things but it doesn't get any better.