Double Decoction Mash Problem Solve
  • jlwjlw
    Posts: 16,454
    On Saturday, my decoction mash went pretty well with the exception that I missed everyone of my step up in temps by 5 to 7 degrees. To correct I would pull another gallon and heat to a boil and then add back into the mash raising the bed to the correct temp. I followed the steps as outlined in beersmith so I am wondering what could have caused the miss each time.


    Mash Schedule: Decoction Mash, Double
    Total Grain Weight: 10 lbs 5.0 oz
    ----------------------------
    Name Description Step Temperat Step Time
    Protein Rest Add 21.62 qt of water at 128.7 F 122.0 F 35 min
    Saccharification Decoct 7.20 qt of mash and boil it 147.0 F 20 min
    Saccharification Decoct 3.59 qt of mash and boil it 156.0 F 20 min
    Mash Out Heat to 168.0 F over 10 min 168.0 F 10 min

    Sparge: Batch sparge with 2 steps (3.79gal, 0.08gal) of 168.0 F water
  • scoobscoob
    Posts: 16,617
    Mash thickness can have a contributing factor in decoction temps due to grain mass, I always add 20 percent to my pulled volume, I boil it and add it back in by the scoopfull until I hit my desired temp and then move on to the next step incorporating the leftover volume from the last decoction if needed, I figure more volume makes it easier to correct for temp with the spare mash than doing another short decoction to pick the temp up to where I need it.
    Jesus didn't wear pants
  • ceanntceannt
    Posts: 53,828
    hhhmmmmm..... always figured it to be evaporation and/or thermal losses.... but the mass may very well be a contributing factor.... I too use the 20% rule, seems to work well.
    Never attribute to malice, that which can adequately be explained by stupidity.
  • ThymThym
    Posts: 121,628
    ceannt said:

    hhhmmmmm..... always figured it to be evaporation and/or thermal losses.... but the mass may very well be a contributing factor.... I too use the 20% rule, seems to work well.



    Evaporation of the decocted wort would reduce the mass on that side of the equation, thus the total heat returned to the mash would be lower.

    Basically anything that either lowers temparatures on either side, or shifts the mass (really the thermal capacity, but mass is a good indication of that) from the decoction to the mash, will cause a lower heat gain and thus temperature rise when the decotion is returned.

    I think the 20% rule is a good way to overcome this from a practical perspective. From a theoretical perspective, I'd bet my @ss that beersmith has the thermodynamics wrong. At a minimum they aren't accounting for all of the major contributors. I've never found it to be anything more than a toy when is comes to formulations.
    The only thing between me and a train wreck is blind luck..... - Kenny
  • jlwjlw
    Posts: 16,454
    Lakewood said:

    ceannt said:

    hhhmmmmm..... always figured it to be evaporation and/or thermal losses.... but the mass may very well be a contributing factor.... I too use the 20% rule, seems to work well.



    From a theoretical perspective, I'd bet my @ss that beersmith has the thermodynamics wrong. At a minimum they aren't accounting for all of the major contributors. I've never found it to be anything more than a toy when is comes to formulations.


    I bet your right. I followed the decoction steps exactly until the last step when I added and 1/2 gallon or maybe a little more and hit the number exact.

    I was playing around with the software last night and was hoping to see a place where I could change the decoction amount. I didn't see anything.

    What I do know is that an 1/2 gallon or so seemed to get me to the correct #. May just need to keep that in mind for future beers.
  • jlwjlw
    Posts: 16,454
    Going to try adding 20% to the volume for the Alt.
  • ceanntceannt
    Posts: 53,828
    If you do the calculations by hand, it might help better to understand how this works….. and use it to check the numbers the software is spitting out… I have a hard time trusting some of the software out there for this type of thing…. I used to be scared ****less of thermodynamics…. This stuff is easy.

    First figure out your total mash volume….
    total pounds grain X 0.08 + volume strike water in gallons = mash volume = Vt


    Vd = decoction volume (pulled to be boiled)
    Vt = total volume of mash (see above)
    T1 = temp. of original mash
    T2 = desired temp. of next rest
    Vd = (T2 – T1) / (212 – T1) X Vt
    Example: mash is at 151, pull decoction to get to mash out at 170. Mash volume is 4.34 gal.
    (170 – 151) / (212 – 151) = 0.2881, X 4.34 = 1.35 gal.
    There you go…. Easier than hittin’ the ground with your hat.
    I’ve been adding 15% to the calculated volume…. Used to do 20%, but had a lot left over after I hit the desired temp.
    Never attribute to malice, that which can adequately be explained by stupidity.
  • jlwjlw
    Posts: 16,454
    did the calc by hand and ended up with 2.08 and beersmith called for 2.25
  • ceanntceannt
    Posts: 53,828
    interesting........
    Never attribute to malice, that which can adequately be explained by stupidity.
  • jlwjlw
    Posts: 16,454
    ceannt said:

    interesting........



    you must understand I suck at math so I could have done something wrong.
  • ceanntceannt
    Posts: 53,828
    jlw said:

    ceannt said:

    interesting........



    you must understand I suck at math so I could have done something wrong.


    Hah!
    It's only around an 8% difference, if you had messed up it probably would have been way more .... the program is probably trying to account for the additional mass of the grain ..... and failing ...
    Never attribute to malice, that which can adequately be explained by stupidity.
  • jlwjlw
    Posts: 16,454
    Do you use the same calculation for mash out. VT stays constant?
  • ceanntceannt
    Posts: 53,828
    Yep..... unless you added additional water in someplace
    Never attribute to malice, that which can adequately be explained by stupidity.
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