How long to mash thick mash?

[BigTerp]

Planning 11 gallons of a Bell's Two Hearted clone this weekend. Going to have to mash thicker to get the 26#'s of grain in my 10 gallon cooler mash tun. Based on some resources, if I mash at 1.10qts/# the entire mash will take up 9.23 gallons in my tun. If I mash at 1.15qts/# the mash will take up 9.56 gallons. Will probably go with 1.10qts/# to ensure I have enough space. A few questions I have regarding this.....

1. Should I mash longer to ensure complete conversion since my mash will be thicker than the normal 1.25qts/# I shoot for? If so, how much longer? An extra 15 minutes? 30 minutes?

2. Since I'll have about 8.25 gallons of sparge water, and the mash being thicker, should I add another step to my batch sparge? Or just batch sparge with two steps using half of my sparge water each time like normal?

3. Anything else I need to consider for mashing this thick?

 

[billl]

1) Shouldn't really matter. If you are concerned, go ahead and let it sit a bit longer. 2 hearted is well attenuated beer, so a slightly more fermentable wort isn't a bad thing.

2) 2 sparges should fit just fine

3) Stir like crazy. The chances of dough balls goes way up with thicker mashes.

 

[doug293cz]

With 26 lbs of grain and 7.15 gal of strike water, your maximum theoretical SG for wort in the initial mash is 1.106. If you have a refractometer, you can monitor the SG of the mash wort. If it gets to 1.106 the mash is done. There is a pretty good chance it could plateau at a lower SG, in which case you might want to accept the less than 100% conversion efficiency, and proceed to run-off.

Brew on

 

[BigTerp]

Thanks for the insight. I actually settled on 1.12qts/# just because it gives me an easier to measure strike water volume of 7.28. With that amount of strike water and 26#'s of grain what can I expect for my first runnings SG to be? I have a refractometer, so I can keep an eye on it like Doug suggested. Thanks again!!

 

[doug293cz]

Thanks for the insight. I actually settled on 1.12qts/# just because it gives me an easier to measure strike water volume of 7.28. With that amount of strike water and 26#'s of grain what can I expect for my first runnings SG to be? I have a refractometer, so I can keep an eye on it like Doug suggested. Thanks again!!

The extra water will drop you max potential SG to between 1.104 & 1.105.

Brew on

 

[BigTerp]

Ended up with a first runnings SG of 1.0974. I'll take it. Mash tun was at its MAX for sure. We'll see what my OG ends up at. Sparging now.

 

[doug293cz]

Ended up with a first runnings SG of 1.0974. I'll take it. Mash tun was at its MAX for sure. We'll see what my OG ends up at. Sparging now.

97.4 / 104.5 = ~93% conversion efficiency. Not too bad for a thick mash.

Brew on

 

[BigTerp]

Thanks for the help man!! How are you figuring those numbers based on strike water volume and #'s of grain? Would be helpful in the future.

 

[BigTerp]

1.056 OG. Target was 1.055. I'm happy!! Slightly higher target pre bill volume though. Thanks again for the help. Really looking forward to this one!!

 

[doug293cz]

Thanks for the help man!! How are you figuring those numbers based on strike water volume and #'s of grain? Would be helpful in the future.

Most base grains have a fine grind, dry basis extract potential of about 80%. This means 80% of the dry weight can be converted to sugar. The moisture content of most grain is about 4% by weight, so the dry weight of the grain that you weigh out is only 96% of what the scale says. So, let's do some calculations with your grain bill and strike volume:

26 lbs of grain * 0.96 * 0.80 = 19.97 lbs of potential extract (sugar)​

You also have

26 lb * 0.04 = 1.04 lb of water from the grain​

You used 7.28 gal of strike water, and water weighs 8.3304 lb/gal (@68°F) so you have

7.28 gal * 8.3304 lb/gal + 1.04 lb = 60.65 lb of water in the mash​

So if you converted all of the starch in the grain into sugar the weight % of sugar in the wort would be:

100% * 19.97 lb / (19.97 lb + 60.65 lb) = 24.77%​

24.77 wt% is 24.77°Plato which converts to a specific gravity of 1.1046. The formula for converting °Plato to SG is:

SG=1+(Plato/(258.6-((Plato/258.2)*227.1)))
​

So, 1.1046 is the maximum possible SG of the wort in the mash, which is also the maximum possible first runnings gravity.

Brew on

 

[billl]

If you don't want to do that calculation, braukaiser has a great writeup on mash conversion with a handy chart of maximum potential for each mash thickness.


http://braukaiser.com/wiki/index.php?title=Understanding_Efficiency