? about calculating gravity, etc

[istuntmanmike]

When using a brewing calculator like BeerSmith, Brewersfriend.com etc (or even just hand-writing the calculations out), what volume should I be using to calculate what the OG should be? The volume that ends up in the fermenter, right?

Also, what is the best method for getting an accurate gravity reading? I know it's supposed to be at 60*, before pitching yeast, and I don't top-off the wort I do full-volume boils. I can't for the life of me hit my target OG, it reads sometimes up to 20 points over OR under depending on the batch (if other people's calculations are correct, hence the first question b/c I'm not sure if my calculations are correct). On my most recent IPA, using 5 gal into the fermenter, the target OG should be 1.096, I measured ~1.086, 10 points low. On another batch, I was expecting ~1.090, I measured 1.108, 18 points high. Dafuq?? How does anybody get an accurate OG reading to be able to determine attenuation, ABV, if the ferment is stuck, etc? Would having hops material in the sample skew the gravity reading? Should it be left to settle for some time before reading?

I'm doing extract brews now, but I don't see how my situation would be any better doing all grain because, again, I'm not topping off with plain water and I thoroughly mix the wort and even whirlpool before racking to the fermenter. If I can't get the wort thoroughly mixed after an hour of boiling and then chilling and whirlpooling, how could I ever get it mixed enough to take an accurate reading? It seems it would be even worse when doing all grain since the OG can vary depending on mash temp; with extract, I'm supposed to hit the calculated gravity easy peasy (supposedly). Maybe I should whirlpool first, take a sample, then chill (and maybe whirlpool again?)?

I'd like to figure out wtf I'm doing incorrectly before continuing/advancing, whether it's calculations or brewing procedures. My beers seem to come out pretty well, but I want my lab results to match my lecture notes/calculations, to borrow terms from chemistry class And I would like to actually know my true attenuation, ABV, etc.

 

[TungstenBeer]

There's a lot going on in this thread, but I'll try to help with the main two questions the most (and they may in fact be related).

1. "What volume would I use on software like Beersmith?" The 'batch volume' in BS is the volume that you will be putting into the fermenter and pitching into. Their standards are 5 or 10 gallons, but you can customize your equipment in the Profiles section. I myself calculate everything to be a 5.5 gallon brew.

2. "How can I get a better gravity reading?" First, make sure your hydrometer is reading correctly by using distilled water (the reading should be 1.000). It wouldn't cause those wild swings like you mention, but at least you'll know if your instrument reads consistently high or low.

Do you always use the same extract in your brews? Do you use the same ones with the right specifications in Beersmith? Not all extracts are made alike, unfortunately. I don't believe that's the real problem though.

How are your volumes? Do you hit 5 (or whatever your target volume is) into the fermenter? Are you dumping some "extra" wort? Or are you coming up with 4.5 gallons, a little short? Obviously those things could greatly affect gravity.

Just some questions to start.

 

[istuntmanmike]

I have two hydrometers and both read 1.000 in water. They read consistently between the two of them.

I don't always use the same extract. I use what the local store has as well as the stuff in
kits from morebeer or elsewhere.

On this IPA, I hit ~5 gallons according to my fermenter bucket. I whirlpooled it in the kettle and left some in there, I started with 6.5gal to boil (1gal from steeping grains+5.5 in the kettle). I had also calculated with 5.5gal but got 5 in the bucket. When I measured the OG I got ~1.086-8, which was the target with 5.5gal. Not sure what went wrong there.

 

[SEABrewer]

I have two hydrometers and both read 1.000 in water. They read consistently between the two of them.

I don't always use the same extract. I use what the local store has as well as the stuff in
kits from morebeer or elsewhere.

On this IPA, I hit ~5 gallons according to my fermenter bucket. I whirlpooled it in the kettle and left some in there, I started with 6.5gal to boil (1gal from steeping grains+5.5 in the kettle). I had also calculated with 5.5gal but got 5 in the bucket. When I measured the OG I got ~1.086-8, which was the target with 5.5gal. Not sure what went wrong there.

How much wort did you leave in your kettle? Could it been as much as half a gallon, meaning you really ended up with a 5.5 gallon batch even though you're only fermenting 5 gallons? The wort doesn't know how big a fermenter you're putting it in, so the total volume produced after the boil is complete and you've topped off with water (if applicable) is what's important. Alternatively, could there be extra wort tied up in your system somehow (e.g. in the whirlpool lines, pumps, etc.) that you're not accounting for in your final volume estimates?

Have you gotten compared the target OG given in the kits/recipes you've used to what Beersmith is telling you? I don't have a lot of experience with Beersmith's gravity targets, but in my experience the target OG on most extract recipes is pretty accurate. If you're missing it wildly on a consistent basis, there's either something wrong with your brewing process (perhaps something very simple) or with how you're reading the gravity.

Another option might be to use a refractometer to see what your OG is. I don't have any direct experience with one, but I've heard they're fairly easy and quite accurate. At a minimum, that'd tell you if you're reading the hydrometer correctly or if you really are missing you target OG. Note that I think you have to do a bit of extra work to use a refractometer to check FG since alcohol will impact the reading.

Oh, and on one of your previous questions, the hops shouldn't impact gravity readings.

 

[SEABrewer]

Another thought is to brew a batch with a partial boil so you have to top off with water to get to 5 gallons (or whatever your target volume is). I'd even recommend taking a gravity ready before and after you top off (and have stirred in the top off water completely) just to get a feel for how the gravity changes in each step.

If you go this route, I'd also recommend skipping the whirlpooling just to take out another variable. There's no reason it should impact the gravity, but it's not strictly necessary (especially if you brew and all extract recipe with limited hops, which is what I'd recommend for this experiment).

 

[istuntmanmike]

How much wort did you leave in your kettle?** Could it been as much as half a gallon, meaning you really ended up with a 5.5 gallon batch even though you're only fermenting 5 gallons?** The wort doesn't know how big a fermenter you're putting it in, so the total volume produced after the boil is complete and you've topped off with water (if applicable) is what's important.** Alternatively, could there be extra wort tied up in your system somehow (e.g. in the whirlpool lines, pumps, etc.) that you're not accounting for in your final volume estimates?

I think this is where I'm making a mistake. I assumed the volume that makes it into the fermenter was the volume to put in the calculator. Guess it should be called volume in kettle at end of boil >.< I boiled 6.5 and left some in the kettle along with most of the hops material, dunno how much though. Using brewersfriend, 5.5 gal volume and 25% efficiency from steeping grains, the OG was what I had measured, 1.087. Only problem now is that it pooped out at 1.028 when i was expecting 1.016...

 

[freisste]

I think we've nailed down the problem. The volume to use is the volume you end up with at the end of the boil IN the boil kettle.

Taken to an extreme:
Pour enough extract into a pot to make a 5 gal batch at 1.050. Add 10 gallons of water. The gravity will be 1.025, right? Now pour 5 gallons of that into a carboy. The gravity doesn't magically rise back to 1.050!

If you want 5 gallons of 1.050 in your fermenter, but you lose 1/2 gal to system losses (hot break, hops in the kettle, racking cane losses, etc), make 5.5 gallons of 1.050 wort. You will have to add 10% to all of your sugar numbers (instead of 1/2 lb crystal xx and 8 lbs of extract, use 0.55 lbs crystal and 8.8lbs of extract).