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Old 01-28-2012, 03:57 AM   #1
Dec 2011
Richmond, VA
Posts: 13
Liked 1 Times on 1 Posts

First, I have only been a member for a month or two, and the amount of information I have garnered from HBT is amazing! I have since assembled a rudementary AG system, and have done three AG batches so far - something I never could have done without HBT. So, thanks everyone for all the info so far even though all I have really done is eve's drop on lots (LOTS) of threads!

Here is my question:

I am looking to make an AG recipe that calls for an acid/protein rest at 112* at the beginning of the mash. Then go up to 158*. I use a cooler for a mash tun so I have no way to heat the mash from 112* to 158* in the mash tun. Could I start the mash in my boil kettle, do the rest, then directly heat the boil kettle (with a propane burner) to 158*-160*, then transfer it to my mash tun (cooler) for the rest of the mash? Then just batch sparge, as usual?

Or will I scorch the grains if I heat the mash with a propane burner in my boil kettle? I could constantly stir?

I can forgo the acid/protein rest if it's not a good idea, but the recipe looks pretty good with the rest!... here's the link to the recipe I was going to try:

Thanks for any input!!

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Old 01-28-2012, 01:57 PM   #2
Jan 2012
Anchorage, Alaska
Posts: 269
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Its called Decoction Mashing a it's type of mash in which at least one mash rest temperature is reached by removing part of the mash, boiling it in a separate vessel, and then mixing it back in to raise the temp of the mash.

Decoction Mash Procedure

The basic procedure for performing a decoction mash is very simple. Water is added to the grist to reach the initial mash temperature. Once the first temperature rest is complete, a portion of the grain and water is scooped out of the mash tun and into the kettle or another heated vessel, where it is brought to a boil. The portion removed, which can often be as much as a third of the grist, is called the decoction.
The decoction may require stirring during heating to avoid scorching the grain; this adds some extra work during the mash. The decoction step also adds time to the mash process, since a decoction cannot be heated as fast as infusion water and it is usually boiled for 5 – 45 min. After boiling, the decoction is returned to the mash tun to achieve the next temperature rest.
The easiest way however is to estimate the decoction volume with a simple formula like this:
decoction volume = total mash volume * (target temp - start temp) / (boil temp - start temp)
and add about 15 - 20%. The idea is to decoct more mash than necessary. When the decoction is added back to the main mash, it is not all added at once. Instead it is added in steps while the temperature of the mash is constantly checked. This requires a thorough mixing of the mash after each addition. Once the target temperature is reached the remaining decoction is left to cool and added once its temperature is close to the mash temperature. By doing so one can account for additional factors that effect the actually needed decoction volume such as: evaporation during the boil, unexpected temperature drop in the main mash and others.

Here is the article I got this from;
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Old 01-28-2012, 02:02 PM   #3
helibrewer's Avatar
Nov 2011
Santa Rosa, CA
Posts: 3,808
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I don't think scorching will be too big an issue since there are numerous RIMS/HERMS systems that use propane burners as the MLT heat source. It is a bit of handling if you are ok with the transfers and you will probably get some heat loss while moving the wort around.

I finally built a heat exchanger using steam from a pressure cooker so I can step mash in my cooler MLT now.
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Old 01-28-2012, 03:54 PM   #4
Oct 2011
Columbia, MO
Posts: 516
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If you have the ability to mash in a directly heatable vessel, like a boil pot, that's going to be way, way, easier and simpler than a decoction. It's possible to scorch, but easy not to if you're careful - I've been mashing in a boil pot using only a tube filter, but a false bottom would be better. You can hold the temp reasonably well by wrapping it with an old blanket or sleeping bag.
A decoction mash may have it's place, but there's no need to do one just to move between temperature rests.

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Old 01-28-2012, 08:59 PM   #5
Dec 2011
Richmond, VA
Posts: 13
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OK. Cool. Thanks for the input.

I definitely don't have the equipment or experience to pull off a decoction mash. But I am going to try starting the mash in my boil kettle so I can go from 112* to 158*. Then I will transfer to my cooler mash tun for the rest of the mash/lauter.

Thanks again for the help, and if anyone else has experience with this please chime in!

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Old 01-28-2012, 10:22 PM   #6
Malticulous's Avatar
Aug 2008
St. George Utah
Posts: 4,146
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I don't see any good reason to do it in a kettle. All you need to do are infusions. Mash in near 1 qt/lb, rest and then infuse to 158. Here is the rakers calculator.

Here is one I did yesterday for a 9 lb 2 oz dunkelweizen. I did one almost like it the day before for a hefeweizen.
  • Mash in 1.32 qt/lb with 120F liquor, rest at 113 for 20 minutes
  • Infuse with 1.8 qt (boiling) rest 122 10 minutes
  • infuse with 6.1 qt, rest 145 30 minutes---at 10 minutes in to this rest I pulled all the thick mash and slowly brought it to a boil, boiled 10 minutes
  • Added most of the decotion to get the mash to 158 (I added the rest of it after it had cooled to 158,) rested 20 minutes. Iodine tested for conversion.
  • Pulled 7 qt thin mash, boiled 20 minutes, added back to mash out, rest 10 minutes, drained
  • Single 14 qt sparge.

It was about 2 hours untill the first runoff and was just under 90% mash efficiency.
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