Ask The Brewmasters

The recent MBAA podcast about wort separation with Travis Audet (https://www.masterbrewerspodcast.com/201) has me wondering about mash thickness. I've traditionally run my mashes at 3:1 grain to liquor without variation and never thought much about it. I've searched the technical papers and looked through my collection of books, and see references to using a ratio between 2:1 up to 5:1, but other than the TQ article from St Arnold, I don't see much discussion as to why.


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Brian Confer
Co-Owner / Head Brewer
Stormcloud Brewing Company
Frankfort, MI
(231) 651-9080
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This message was posted by a user wishing to remain anonymous

Mash thickness can also influence your conversion. A thicker mash could help buffer your enzymes from denaturing by temperature, but at the same time, if it's too thick they may not be able to thoroughly mix and convert your starch. On the flip side, a thinner mash would allow enzymes to flow more freely and break down starch, but are also more susceptible to temperature and could denature more.
That said, when I've seen changes made to density it has been in an effort to improve lautering. Working with both a lauter tun and a mash tun, we have seen the effect of changing our mash density even in our mash tun. If you're trying to change mouthfeel by adjusting how well you're converting, you may be better off changing your ingredients to something that will change mouthfeel and making sure you fully convert.

I agree that as long as you're within a fairly typical range, the biggest impact of adjusting mash thickness will be on lautering. If you navigate to https://sites.google.com/site/republicbrewpub and download the Sims_CS_WER spreadsheet, you can see some curves that illustrate the impact. They're from simulations of a hypothetical near-perfect lauter tun - so reading numbers directly off the graphs won't do much for you - but they're useful for understanding general trends. For what it's worth, I've tweaked the assumptions for various breweries where I've worked to use the model for recipe formulation and mid-lauter adjustments.

The RE vs. KV tab shows runoff extract from the lauter tun outlet vs. total runoff volume. The horizontal lines representing first runnings extract aren't representative of what really happens, but they're useful for estimating kettle extract at the point when sparge water begins to enter the lauter tun outlet - and since you shouldn't cut off a lauter before that point, what happens beforehand doesn't much matter for what we're talking about. The KE vs. KV tab shows kettle extract under the same conditions, and the BE vs. KE tab shows how your target runoff extract will impact brewhouse efficiency at various liquor-to-grist ratios. The curves refer to water-to-extract ratios instead of water-to-grain ratios to eliminate grain yields as a simulation factor, but they'll both track with extract in similar ways. The WER values are in qt/lb - so you can roughly multiply them by 2 to estimate L/kg - and the "reference" referred to in the X asis is 15 lbs of wort per lb of grain, which translates to 45.4 bbl for a 1000-lb grainbill with a CGAI of 78%.

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Joe Walts
Lab Technician
Octopi Brewing
Madison WI
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Original Message:
Sent: 04-01-2021 12:39
From: Anonymous Member
Subject: Liquor-to-Grist Ratio

This message was posted by a user wishing to remain anonymous

Mash thickness can also influence your conversion. A thicker mash could help buffer your enzymes from denaturing by temperature, but at the same time, if it's too thick they may not be able to thoroughly mix and convert your starch. On the flip side, a thinner mash would allow enzymes to flow more freely and break down starch, but are also more susceptible to temperature and could denature more.
That said, when I've seen changes made to density it has been in an effort to improve lautering. Working with both a lauter tun and a mash tun, we have seen the effect of changing our mash density even in our mash tun. If you're trying to change mouthfeel by adjusting how well you're converting, you may be better off changing your ingredients to something that will change mouthfeel and making sure you fully convert.

From our experience with our IPA on a combi-vessel system, we've found LG-ratio impacts both mash efficiency and lautering performance (differential pressure during collection). In both cases, however, it hasn't had an impact on its own (p = 0.963 and p = 0.651, respectively), but rather in conjunction with other factors.

With mash efficiency, the impact of LG-ratio is significant in interactions with vorlauf time fraction (fraction of conversion+vorlauf time) (p = 0.002), diastatic power of the base malt lot (p = 0.0163), and to a much lesser extent, lower mill gap setting (p = 0.276). With lautering performance - which among others things we define as the mean dP throughout collection - the impact of LG-ratio is significant in interaction with total mash time (p = 0.029).

Below are some graphs of the models - note that our LG-ratio is in qt/lb, so roughly double that to get the w/w ratio.

Also, a key:

This model graph suggests that mash efficiency in thicker mashes (lower ratios) benefit from longer vorlauf times (relative to conversion time, so for example, if your total mash time is 60 minutes, a vorlauf fraction of 0.75 would be a 15 minute conversion and 45 minute vorlauf). And vice versa - mash efficiency in thinner mashes tends to benefit from shorter relative vorlauf times (using the 60 minute total mash time again, this would be a 54 minute conversion time and 6 minute vorlauf). I have no idea why this would be, but the anonymous post above may be on to something. 

Below is the model showing impact of LG-ratio interacting with diastatic power. It suggests thicker mashes can minimize the impact of diastatic power, but if you have a good diastatic power, you may really be able to bump your mash efficiency by using a thinner mash.

The lower mill gap setting graph isn't as cool (hence the higher p-value), but a smaller lower mill gap seems to help mash efficiency in thicker mashes. This tends to be the case with finer grist, but careful with fine grist in thick mashes. Lautering performance will more than likely be affected.



A quick note about the dP model: it's not the most reliable at predicting due to the data coming from production runs. In other words, the higher dP runs are interfered with (of course), so the actual numbers are artificially low. But we do think the general relationships remain intact. 

Anyway, for lower dP in thicker mashes, the model suggests longer total mash times (regardless of vorlauf fraction). It seems to care less about total mash time as the mash gets thinner (for lautering performance - not necessarily mash efficiency).


And one final disclaimer: this is for one brand in our production brewhouse. Your mileage may vary. 

Hope this helps, cheers!


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Trent Leslie
MadTree Brewing Company
Cincinnati OH
(419) 651-5914
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