Author Topic: PostMash gravity  (Read 1814 times)

Offline JuanAssis

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PostMash gravity
« on: August 22, 2020, 08:01:45 PM »
Hello everybody!
I'm a recent BeerSmith user and I don't know all things that I need.
So, I want know an estimated post mesh gravity without consider sparge water, but the Beersmith is considering for "Post Mash Gravity " cell.
This gravity is easy to calculate, but I don't want need to calculate.
Someone can help me with this?

Thanks!

Offline Oginme

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Re: PostMash gravity
« Reply #1 on: August 23, 2020, 06:43:51 AM »
If I follow you correctly, you are looking for the program to give you the gravity of your first runnings from the mash (i.e. the gravity before any sparge water is added).  This is a function of the water to grist ratio, your conversion efficiency, and the limits of sugar solubility in the wort. It also does not take into account any dead space water which is in the mash tun, nor the sugars which will diffuse from the wort in the mash into the water not in contact with the grist, which would be a time dependent function.

The program does not know your conversion efficiency and would only be able to default to the maximum concentration of sugars in the water.  This is well described by Kai Troister at http://braukaiser.com/wiki/index.php/Troubleshooting_Brewhouse_Efficiency#Determining_Conversion_Efficiency

While this is interesting information for troubleshooting your conversion efficiency, it can also be calculated based upon the total extraction of sugars which is described further down the page on that same link referenced above.  It is valuable for a post-mortem, but not a critical target for most brewers during the brew session.  Any target the program estimates is highly suspect, as it does not know your sparge efficiency vs the conversion efficiency. 

When I did perform a more traditional batch sparge (and for a short period of time, fly sparge), I would measure the first runnings versus the pre-boil gravity and the gravity of the second runnings.  It did help in pointing me to lengthen my batch sparge time and drainage rate to maximize the extraction of the remaining sugars left in the wort.  I also was able to optimize the water to grain ratio of my initial infusion to improve my overall mash efficiency, but again, this was a post mortem analysis and not a brew day function.

Bottom line is that this information is useful to those of us who do a deep dive into the process, but for most brewers would not be very useful.  Further, in my opinion, it is not an analysis which I would rely on the software to give me a dependable target. 
« Last Edit: August 23, 2020, 09:41:41 AM by Oginme »
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