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-   -   Beersmith gravity calc (http://www.homebrewtalk.com/f84/beersmith-gravity-calc-39204/)

Cos 09-19-2007 05:59 PM

Beersmith gravity calc
Beersmith gives me an estimated pre-boil gravity. Is that temperature corrected?

When doing a partial mash, prior to adding DME to the boil, how are you calculating the amount of DME to add?

I deleted the DME from beersmith and then compared the calculated preboil gravity to my actual preboil gravity. They were the same, so I added what the recipe called for in DME. When I got done, my actual OG was 4 points lower than beersmith estimated.

bradsul 09-19-2007 06:03 PM

There is no temperature correction in the calculation of specific gravity. The temperature correction is necessary during measurement because of the way a hydrometer works.

I've not used Beersmith so I'm not sure how it does the calculation. But normally you'd have a target OG you were shooting for, so you would just add DME until you hit that mark.

The DME that you used may have had a different potential gravity than what Beersmith had in its database. Also your partial mash may not have been as efficient as the recipe was designed for (maybe you got 70% extraction instead of the 75% the recipe was calculated for).

Cos 09-21-2007 02:45 AM

If my efficiency was less, then my measured preboil gravity should have been less than the beersmith calculated preboil gravity.

FlyGuy 09-21-2007 03:05 AM

Four points is pretty small. Are you sure you got your volumes correct? That would really matter.

BierMuncher 09-21-2007 03:07 AM

The one factor you're overlooking is your own "efficiency". Basically, the effectiveness of extracting fermentable sugars from your mash grains. Beersmith disables this variable for extract brews, but for PM and AG, it's key.

You can add exactly what beersmith calls for in DME to hit a target OG, but if you mashed your grains poorly, you've already fallen short.

You'll have to deal with the same thing AG brewers do, and that's determining your own brewshop efficiency and adjusting your recipes accordingly.

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