Strike water volume for 5 gallons mash tun

[Kassad]

When doing all grain and calculating water to add to 5 gallon mash tun, is it better to add more water for a thinner mash if your mash tun can accommodate? I have seen videos where people use 1.5qts/lb and I've seen recipes (morebeer.com) that call for 1.1qts/lb.

There are 5 gallon grain bill recipes, like a Kolsch I have my eye on, that have a 10.5 lb total grain bill. If you go with 1.1 qts/lb then the water you need for mash-in is 2.89 gallons. If wet grains occupy .33qt/lb then 10.5 pounds takes up .87 gallons. Add that to your 2.89 gallons of strike water and your total mash volume should be around 3.75 gallons. That head space may, or may not have an effect on the 60 minute 150 degree temperature we strive for, but it would affect the efficiency differently than if you used 1.5qts/lb of grain right?

That same 10.5 pound grain bill using 1.5qts/lb would still fit in a 5 gallon mash tun, even taking into account the space occupied by wet grains. 10.5lbs * 1.5qts/lb = 3.94 gallons of strike water. Total volume = 3.94+.87 = 4.8 gallons total space occupied (grains and water).

So would you rather have a thinner mash consistency, or a thicker?

 

[McKnuckle]

Answers will be all over the place on this one. Like everything in brewing, it matters, but perhaps not so much to justify obsessing over it.

One very simple way to go about it is just to determine the total amount of water you need for your brew, including all losses, and divide it in half. Mash with half, sparge with the other half. With this approach, you basically ignore the mash thickness but it always works out fine, maybe between 1.4-1.7 qt/lb depending on the target OG.

Temperature stability is affected by thickness and head space. The less headspace, the more stable the temp. The thicker the mash, the more stable the temp. In a way those are counter to each other - if you fill up the mash tun, it's a thinner mash but you minimize headspace. Again, a reason not to obsess over it, and to focus on other more practical aspects of the mash.

Another practical aspect is achieving an appropriate mash pH. The thinner the mash, especially for a pale beer, the more acidification it will likely need. Perhaps it's easier to stay thicker for that reason. For a dark beer, the opposite is true - more water may help buffer the acidity.

See where this all goes? I just divide my water in half unless I'm going for multiple infusions.

 

[jalc6927]

Agreed with Mcnuckle

There are more ways and opinions on this than stars in the sky

You need to try it one or two different ways until you find a method that works,

Half and half is a great place to start

 

[helibrewer]

A happy medium is a liquor:grist of 3:1 which in homebrewing measurements would be 1.42qts/lb of grain

Thin mashes tend to produce lower fermentability/higher extract than thicker mashes (higher fermentability/lower extract). These differences are due to physics, the thicker mash provides better protection for beta-amylase which is more heat sensitive than alpha-amylase.

There is much higher heat loss through the sides and bottom of a MT than through the head space and this of course is dependent on the material and insulation qualities of the vessel.

The thermal conductivity of air is .024 W/(mK)
Stainless is 16 W/(mK)
Aluminum is 205 W/(mK)

So air is a far better insulator than any material your vessel is made from.

 

[SoCal-Doug]

I'm not sure if you are recirculating or not, but if you are, let me throw an alternative theory out there to ponder on...

Back in the older days when the whole quart per gallon thing was written about and discussed, most people had static grain beds in coolers and pots without recirculation. It was fairly loose and many people would occasionally stir the mash. You could easily adjust from a dense or soupy mash by adjusting the qt/gal ratio. It does make a slight difference in results but I was never convinced that I could measure or taste a difference between a 1.1 and a 1.6. Oh, and before I digress, a little more water will provide a bit of additional level of temperature stability. But it's probably not enough to nitpick about.

Fast forward to systems that continuously recirculate, there is not only gravity in play, but the downward flow of the wort. Picture this scenario... You have 10 pounds of grain in your MLT and whatever amount of water to completely hydrate the grain and be 1 inch above the top of the grain bed. You are happily mashing and recirculating. The wort above the grain is nice and clear and all is good. Your grain is not as free to move around and expand as it would be if you were not circulating. Their is a small amount of compaction happening. You have gravity, weight of grain and weight of water giving your grain bed "X" level of compaction and density.

Now do that same mash again, but add more water this time and its 2 inches above the grain bed. Again you are happily mashing and recirculating. Your water to grain ratio is definitely higher than the last example, however, your level of grain compaction and density has slightly increased. This would have the same effect as actually lowering your water to grain ratio in a static mash, therefore being inversely proportional by some mathematical factor.

Take it to an extreme for a moment. Recirculate your mash with 12" of water over the grain bed. Maybe the ratio now is 10 quarts per pound, instead of 1.25 quarts per pound. Is the grain any looser or less dense than the first example? No. In theory, its more dense. It still finds its happy compaction level as the alpha and beta chew on the starches.

On my rig, I calculate strike/mash water as 1.2qt/lb (assuring grain absorption) plus the volume under the false bottom, plus the capacity of the lines, pump and coils, plus another 1.15 gallons which assures roughly 1.5 inches of wort above the grain bed in a 15" diameter kettle. If you take that total number as a qt/grain ratio, it would be crazy high. But in a recirculating system, is the excess wort above the grain any more relevant than the wort in the lines and HERMS coil? I think not.

Long story short. My opinion is if you are continuously recirculating, your water to grain ratio is irrelevant once the volume assures the entire grain bed is submerged, and may effect the results inversely to a ratio applied in a static mash process. If the recirculation rate and wort layer above the grain stays pretty close to the same, for each recipe, your compaction and final results should remain a constant and repeatable.

If you are not recirculating, ignore everything I said

 

[Hwk-I-St8]

I try to match the output of the first and second runnings. I use brew365.com and tweak things until the second runnings volume equals have of the pre-boil volume.

 

[DurtyChemist]

I go with 1.25 qts/lb. I haven't brewed anything much bigger than 1.060 in my 10 gallon mash tun as a 10 gallon batch.