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-   -   iBrewMaster OG Calcs w/ Mash Temps (http://www.homebrewtalk.com/f84/ibrewmaster-og-calcs-w-mash-temps-358561/)

D-Hutt 10-03-2012 06:54 PM

iBrewMaster OG Calcs w/ Mash Temps
Are the OG calculations in IBM disconnected from the mash temperature you use? Seems like the OG should vary depending on how fermentable my wort is, but I don't see any change in the app when I vary the temps of my mash. Is this just a missing feature? Or do I have something set up incorrectly?

alestateyall 10-04-2012 12:52 PM

The OG depends on the efficiency input. If you believe your OG will increase you can adjust your efficiency.

By the way, the OG does not really depend on mash temp or fermentability of the wort. The OG is gravity before fermentation. The FG does depend on mash temp and fermentability. iBrewMaster does not automatically adjust FG based on mash temp. FG is derived from the attenuation input. If you believe decreasing mash temp will significantly change your FG you can cause iBrewmaster to predict this by adjusting the attenuation assumption.

On last thing, in my experience mash temp does affect attenuation but I have had very little success trying to predict attention based in mash temp.

D-Hutt 10-04-2012 12:58 PM

You're right - I have no clue why I put OG. I meant FG. Where is the attenuation assumption located in ibm? I'll have to play around with that a bit. Would be cool if it did it automatically based on the mash temp in the Mash Steps section. But if you're right and it's hard to predict, maybe that's why the feature isn't there.

alestateyall 10-04-2012 01:00 PM

In your recipe or batch click on the yeast. The attenuation is the last item in the list above the sliders.

MalFet 10-04-2012 01:05 PM

FG is the result of an extremely complex system, and to my knowledge there are no good models to combine all of these factors. If anyone goes to the trouble of deriving one, I'm sure the software designers would be thrilled to use it.

D-Hutt 10-04-2012 01:26 PM

That person won't be me, lol. Ok, I'll try to make do w/ adjusting attenuation of the yeast and keeping records of where I end up.

HollisBT 10-04-2012 03:37 PM

I have always found IBM's FG calculations to be pretty inaccurate... And no, they are not connected to mash temps at all.

Fwiw, any calculations for FG are pretty much just guesses. I have better luck turning off auto calculate for that field and taking my own guess based on my own brewing data. Also, mash temp is not the only factor for guessing the FG, your grain bill will also play a role in it.

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