Gravity readings don't add up

Hey everyone, I've made two different beers so far and the gravity measurements aren't agreeing with my math.

For example, I did an Imperial IPA that is supposed to have a starting gravity of 1.097 according to the recipe I found and a brewing software I'm using. But when I measured it, it's 1.075. I adjusted for temperature and I checked the hydrometer against water and it works fine.

Similarly with a chocolate stout I made, it's supposed to be 1.054 but it started at 1.042.

I do steeping partial mashes. I've been doing concentrated 3.5 gallon steeps and boils, then adding water before fermentation.

Any ideas why my gravities and subsequent ABVs are so far off?

Thanks for any ideas. Let me know if you need more details.

My guess is that your top off water was not thoroughly mixed in when you took the measurement. It has to be mixed VERY well or you will not get accurate results.

Another possibility is that your volume is not correct. How are you measuring the final volume? If you are using the lines on a Pale Ale bucket or the like, they are notoriously inaccurate.

Just a couple thoughts...

BTH, welcome to HBT!!!

Hmm, that would make sense. We've been thinking about adding our top-off water to the brewpot at the end of the boil so it'll sanitize and not interrupt our cooling process and pitching schedule. Plus it'll probably mix better like you suggest.

And yah the measurements are based on the fermenter bucket kit.

So you're saying I should probably trust the math a little bit more than I trust our hydrometer?

CmdrTrekk said:

Hmm, that would make sense. We've been thinking about adding our top-off water to the brewpot at the end of the boil so it'll sanitize and not interrupt our cooling process and pitching schedule. Plus it'll probably mix better like you suggest.

And yah the measurements are based on the fermenter bucket kit.

So you're saying I should probably trust the math a little bit more than I trust our hydrometer?

Click to expand...

If you can do a full volume boil, you'd be better off (most starting out don't have a Boil Kettle large enough to do full boils).

Use a known volume container (a measuring cup), to measure out a gallon in a pitcher then remark your bucket.

Trust the hydrometer... just make sure you have your wort very thoroughly mixed before measuring.

another option would be to take the hydrometer reading before topping off and just adjust for the added water, i.e. post-boil volume * post-boil SG = topped off volume * topped off SG

Ohio-Ed said:

My guess is that your top off water was not thoroughly mixed in when you took the measurement. It has to be mixed VERY well or you will not get accurate results.

Another possibility is that your volume is not correct. How are you measuring the final volume? If you are using the lines on a Pale Ale bucket or the like, they are notoriously inaccurate.

Just a couple thoughts...

BTH, welcome to HBT!!!

Click to expand...

In my partials when I add water to "top off" I check gravity AFTER rocking bucket for 15 min. I did a test and gravity points varied big time between pre and post aeration rocking. I got an additional .015 after 15min shake on a similar OG as yours . Big worts don't naturally blend quickly with water when topped off.... think of it as a BIG 5 gallon Black & Tan... Guinness floats on top of Bass = Water floats on top of big wort (even more so as distilled water is 1.000)

dcp27 come to think of I think that's what I've been doing. I take the hydrometer reading off the bottom of the brewpot before doing the top-off. So that means it's based on 3.5 gallons (ish). Is there a way to adjust that reading to the full 5 gallons?

I tend not to want to put my turkey baster into the fermenter. But maybe I should since I've been fully sanitizing it anyway.

Either way it sounds like I need to make adjustments to my measuring methods.

dcp27 said:

another option would be to take the hydrometer reading before topping off and just adjust for the added water, i.e. post-boil volume * post-boil SG = topped off volume * topped off SG

Click to expand...

dcp27, come to think of I think that's what I've been doing. I take the hydrometer reading off the bottom of the brewpot before doing the top-off. So that means it's based on 3.5 gallons (ish). Is there a way to adjust that reading to the full 5 gallons?

I tend not to want to put my turkey baster into the fermenter. But maybe I should since I've been fully sanitizing it anyway.

Either way it sounds like I need to make adjustments to my measuring methods.

CmdrTrekk said:

dcp27, come to think of I think that's what I've been doing. I take the hydrometer reading off the bottom of the brewpot before doing the top-off. So that means it's based on 3.5 gallons (ish). Is there a way to adjust that reading to the full 5 gallons?

I tend not to want to put my turkey baster into the fermenter. But maybe I should since I've been fully sanitizing it anyway.

Either way it sounds like I need to make adjustments to my measuring methods.

Click to expand...

Those #'s were pre top-off? That doesn't make sense, since if its low at 3.5 gallons, its gunna be way low at 5g.

1.075 at 3.5gal is 1.0525 at 5gal. 1.042 at 3.5gal is 1.0294 at 5gal

CmdrTrekk said:

I tend not to want to put my turkey baster into the fermenter. But maybe I should since I've been fully sanitizing it anyway.

Either way it sounds like I need to make adjustments to my measuring methods.

Click to expand...

As long as you are fully sanitized, there is no big deal in pulling out some with a pipette err turkey baster. Maybe buy a new one and dedicate it to the purpose. Thoroughly sanitize, including yourself and whatever you touch. I use starsan and a pipette; never had a bad batch.

dcp27 said:

Those #'s were pre top-off? That doesn't make sense, since if its low at 3.5 gallons, its gunna be way low at 5g.

1.075 at 3.5gal is 1.0525 at 5gal. 1.042 at 3.5gal is 1.0294 at 5gal

Click to expand...

Yah...that's what I thought. It's really bizarre. Kind of annoying. I also think getting some of the hops sediment probably screwed it up too. Overall, probably really didn't take the measurement right at all.

I'll have to make sure I'm way more specific about how I'm measuring and when. Taking into account all of the advice here and see if that can correct some of the errors. It's of course really messing up my IBU count too.

triethylborane said:

As long as you are fully sanitized, there is no big deal in pulling out some with a pipette err turkey baster. Maybe buy a new one and dedicate it to the purpose. Thoroughly sanitize, including yourself and whatever you touch. I use starsan and a pipette; never had a bad batch.

Click to expand...

+1 on dedicated turkey baster $1 at dollar tree $1.25 @ walmart. I have 3! 2 still in package. Starsan is your friend! No Rinse! Don't fear the foam!

Update: My temperature adjustments were wrong, the gravity is actually 1.081 because it was at 90* The table I got for adjustments was unreliable. So I'm not too far off. And with the explanations y'all gave between unmixed water and too much hop content in the hydrometer, I think I'm okay.

Thanks everyone.

CmdrTrekk said:

Update: My temperature adjustments were wrong, the gravity is actually 1.081 because it was at 90* The table I got for adjustments was unreliable. So I'm not too far off. And with the explanations y'all gave between unmixed water and too much hop content in the hydrometer, I think I'm okay.

Thanks everyone.

Click to expand...

Glad to hear you're actually closer than you thought, but fyi, hop content or any other particulate won't affect a hydrometer reading unless its actually clinging to it and weighing it down. Because its a measure of density, only the temperature and content (sugar, alcohol, etc) dissolved in the wort will effect it.

Ah, duly noted. Thanks again. I'll keep working on proper technique.