Help with gravity readings

[nreed]

Hi all,

I've just started reading my gravity a few brews in and I just want to make sure I'm reading things correctly. I use a refractometer which only shows Brix so have been using the BeerSmith conversion tool.

My OG came up quite short at 10 brix - I also used a hydrometer to confim which read 1.040. The recipe was aiming for 1.048 which I think was due to my mash temps being too low.

Pitched yeast Saturday afternoon, bubbled nicely over Sunday/Monday and slowed down yesterday. Took my first reading today and it's at 5 brix which BeerSmith tells me is 1.007, with my estimated final gravity being 1.010. Does this mean it's done already?

For reference, it's a Hazy Pale Ale recipe, small batch (7.5l), fementing in my chamber at 19C - i'd just turned it up to 20.5C as it slowed down to keep the yeast going maybe no need?

 

[VikeMan]

My OG came up quite short at 10 brix - I also used a hydrometer to confim which read 1.040. The recipe was aiming for 1.048 which I think was due to my mash temps being too low.

Pitched yeast Saturday afternoon, bubbled nicely over Sunday/Monday and slowed down yesterday. Took my first reading today and it's at 5 brix which BeerSmith tells me is 1.007, with my estimated final gravity being 1.010. Does this mean it's done already?

It doesn't (necessarily) mean it's done. It means your SG is currently lower than what BeerSmith told you to expect. Check again in 2-3 days and see if it's stable. That said, my guess would be that it's done, since you're at over 82% apparent attenuation.

BeerSmith doesn't consider the makeup of your grist when predicting FG (i.e. attenuation). If you post your grain, mash temp, mash length, and yeast strain, I can tell you what my sheet would predict. Still, it's just a prediction.

For reference, it's a Hazy Pale Ale recipe, small batch (7.5l), fementing in my chamber at 19C - i'd just turned it up to 20.5C as it slowed down to keep the yeast going maybe no need?

There's a lot more than just attenuation that happens during fermentation. The yeast will often still be cleaning up off flavor compounds after FG is reached, and bumping the temp up a little can help expedite that.

 

[RM-MN]

I'd suspect a coarse crush of the grain as the cause of a low OG. Most brew shops don't set their mills at the optimum gap as it then can cause customers to get stuck sparges and they complain more about that than a lower than expected OG. There are a few ways to fix that or at least improve it. One is to simply adjust the recipe to account for a poorer efficiency than it was written for. Another is to extend the mash period from 60 to 90 minutes. The best way is to get your own mill and then buy grains in bulk so you can brew when you want, get the savings from buying in bulk, and the the efficiency you expect.

With a good pitch of yeast and proper temperature the beer will reach the FG quite quickly. That FG is only an approximation because yeast are a living organism and sometimes they do better than expected. Raising the temperature when the fermentation slows allows the yeast to stay active and clean up byproducts. I'd probably give the beer quite a bit more time as the fermentation stirred up all the trub and it takes time for it to settle out. I usually leave my beer in the fermenter for about 3 weeks before bottling.

 

[Funky Frank]

Plug 5 brix into the calculator again. Brix and sg are both linear scales so if 10 is 1.040 then 5 should be 1.020.

As for not hitting your recipe’s desired og, your mashing process is likely the culprit. Make sure you are in an appropriate temp for an appropriate time, add a mashout to your mash process (10 min at 168 F or 75.5 C), and some kind of simple sparge. Those things should improve your efficiency.

 

[VikeMan]

Plug 5 brix into the calculator again. Brix and sg are both linear scales so if 10 is 1.040 then 5 should be 1.020.

Alcohol skews refractometer readings. The SG of 1.007 posted by the OP is a corrected reading.

 

[Funky Frank]

Wow! Good call! I’ll chalk that up to the time and trying to multitask...lol

 

[nreed]

BeerSmith doesn't consider the makeup of your grist when predicting FG (i.e. attenuation). If you post your grain, mash temp, mash length, and yeast strain, I can tell you what my sheet would predict. Still, it's just a prediction.

Thanks it was 1.54kg of Pale Malt, 160g of Wheat Malt and 160g of Flaked Oats, total water volume for mash and sparge was 11.5l.

Mash temp came out low at 62-63C, I usually hit my 66C target by taking the water to 74C but must have taken a bad temp reading or maybe grain was colder than expected due to the cold weather here in UK(?).. mashed for 60 minutes. Pitched with half a pack of US-05.

The yeast will often still be cleaning up off flavor compounds after FG is reached, and bumping the temp up a little can help expedite that.

If I get consistant readings over the next couple of days, is there a benefit to keeping it on the yeast for longer or should I go ahead and bottle?

 

[VikeMan]

Thanks it was 1.54kg of Pale Malt, 160g of Wheat Malt and 160g of Flaked Oats, total water volume for mash and sparge was 11.5l.

Mash temp came out low at 62-63C, I usually hit my 66C target by taking the water to 74C but must have taken a bad temp reading or maybe grain was colder than expected due to the cold weather here in UK(?).. mashed for 60 minutes. Pitched with half a pack of US-05.

With an OG of 1.040 and the above specs, I'm coming up with an FG prediction of 1.009-1.010.

If I get consistant readings over the next couple of days, is there a benefit to keeping it on the yeast for longer or should I go ahead and bottle?

The yeast may be still cleaning up off flavors. I'd recommend tasting before bottling.
Also, you don't need to take readings over the next couple days (i.e. each day). Just can wait 2-3 days and measure again (once).