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Evan! · 09-06-2006, 05:42 PM

Okay, so, I've never bothered with gravity readings before, and my beers have all come out fine. But now, I'm running into some issues/problems that would be helped if I knew the current gravity of the beer, and also what my final gravity SHOULD be.

While I don't have actual original gravity readings, I DO have ProMash gravity calculations based on what I put into the beers, so I think I can count on them for my OG readings. Anyway, I need to figure out whether my Barleywine needs more fermentation; I need to find out if the additional 1-gallon "second boil" that I added to my punkin beer is actually fermenting out; I need to find out if I can safely rack my Imperial stout to secondary.

I need to know: if I have, say, 1.092 for my original specific gravity, what should it be before racking to secondary? What should FG be? I know there's a conversion, but dunno what it is. Thanks!

**the_bird** · 09-06-2006, 05:49 PM

ProMash doesn't give FG calculations as well? That's odd...

johnsma22 · 09-06-2006, 07:10 PM

Basically, once you have reached about 75% attenuation from your OG reading that is about as much as can be expected from your yeast. Check the yeast strain that you used to find how attenuative it is. For example, if your OG was 1.092 and your yeast has an expected attenuation of 75%, then when the gravity has fallen to about 1.023 then you know that you are pretty much there, as 1.023 is 75% of 1.092.

John

homebrewer_99 · 09-06-2006, 08:36 PM

I agree with johnsma...

Evan! · 09-06-2006, 09:58 PM

Cool, thanks you guys. Now I see what I was looking for! ProMash has a recipe database, which is where I was looking; however, it also has a "session" database for when you brew. You plug in your recipe, then enter specifics like which yeast you use, ho wlong fermentation is, when you bottle, etc. So, since I entered the yeasts for that section, it says my FG should be 1.012 for the Imperial Stout. Excellent.

Funny how I've brewed 50 gallons of beer and never worried about this stuff before.

mysterio · 09-06-2006, 10:12 PM

Your FG depends on so many factors that promash cannot be reasonably expected to calculate it. While I agree with john, there is a good chance that a beer with that high a gravity will not attenuate down that far. The main factors are mash temperature, use of adjuncts (carapils, sugar?), yeast type, pitching rate, aeration, and fermentation conditions. Probably a few others, too.

For example, say you had a 1.040 pale ale with half a pound of brown sugar in it, and you pitched a packet of nottingham. You could reasonably expect the beer to drop to around 1.008 or lower. The same ale with a london strain, no sugar, and a lot of crystal malt probably will end up somewhere around 1.015.

I would have quite a lot of trouble getting a 1.092 stout down to 1.012, I reckon, but good luck.

Evan! · 09-07-2006, 01:02 PM

msyterio:

We'll see. ProMash has variable inputs for pretty much everything I used in that batch, short of the unsweetened baking chocolate and the coffee. For instance, when calculating final gravity, it takes into account the fact that I used various types of sugars, including molassas; it takes into account yeast type, fermentation temps, and other factors. Might not be perfect, but it seems as close to it as a bunch of ones and zeroes can be.