Specific Gravity Corrections

[Kegger320]

OK, I'm on my 4th all-grain brew and I thought I did everything correctly on this one but my Pre-Boil gravity came out really low. It was a very hot day here in sunny Texas, probably not the best brew day but you might have to wait a couple of months to brew in Texas to get down to the 80's.

Big question, are the temperature corrections for gravity accurate at high temps., otherwise I'm going to wind up with some lightly colored mouthwash!

It was an Amarillo Pale Ale with 9.66lbs of grain and wound up with 6.75gals of wort. I ended the sparge at 1.010.

Pre-boil OG was 1.018 @ 156*f which came out to a temp corrected gravity of 1.039 vs. the recipe's 1.042.

My question is if these temperature corrections are accurate at these high wort temps, because otherwise my pre-boil gravity was even lower.

I ended up boiling the wort for 30 extra minutes to try and get the gravity up a bit and wound up with a post-boil gravity of 1.035 @ 124*f(corrected for temp = 1.046) which was close to the recipe's 1.047.

Am I just being paranoid or did I screw up the batch.

Jim

 

[peterj]

From what I've heard and read, correcting the reading for that high of a temperature is not very accurate. You should cool your sample down to at least 80 degrees before you take the reading. I usually just cool it down to what the hydrometer is calibrated to (mine is 60F). It doesn't take very long at all. Just put the sample in a small ice bath for a couple minutes.

That being said, your corrected gravity measurements are probably somewhere in the ballpark, so I wouldn't worry about it too much. I would just cool your samples on the next brew.

 

[jCOSbrew]

Did you hit your target gravity into the fermentor?
The hydro temp correction is not very accurate. You could let the sample cool to room temp or invest in a refractometer for easy gravity readings during the brew session.

 

[flars]

There is more of a variance in the temperature correction calculators at higher temperatures for the sample. the variance does not amount to much though. It looks like you had the right procedure. If you saved your sample you can recheck at a lower temperature.

It is handy to keep a glass of ice water around for quick chilling the samples.

 

[Kegger320]

From what I've heard and read, correcting the reading for that high of a temperature is not very accurate. You should cool your sample down to at least 80 degrees before you take the reading. I usually just cool it down to what the hydrometer is calibrated to (mine is 60F). It doesn't take very long at all. Just put the sample in a small ice bath for a couple minutes.

That being said, your corrected gravity measurements are probably somewhere in the ballpark, so I wouldn't worry about it too much. I would just cool your samples on the next brew.

I thought I remembered reading that it wasn't very accurate at high temps. That's a great idea, ill just throw it in an ice bath for a couple of minutes.

Thanks.

 

[balrog]

What Peterj says. Bottom line, if you're within 3 pts of expected, you're done.

 

[HungusBrews]

I would consider 1 gravity point off a success! As for accuracy at high temps, just make sure the calculator you are using has incorporated that temp in its range. For example, http://www.brewersfriend.com/hydrometer-temp/ goes up to 159 so you can't use it higher than that. If you really want to quickly and accurately measure wort at different points through the lauter, invest in a refractometer.

 

[Kegger320]

Did you hit your target gravity into the fermentor?
The hydro temp correction is not very accurate. You could let the sample cool to room temp or invest in a refractometer for easy gravity readings during the brew session.

I ended up boiling it for an additional 30 minutes and my final gravity was pretty much right on, but that was corrected for temperature of the wort at about 122*f

 

[Kegger320]

What Peterj says. Bottom line, if you're within 3 pts of expected, you're done.

If the corrected temp(from Beersmith at 156*f) is correct i was within .003 of the recipe. If the corrected temperature was wrong I was nowhere close as my pre-boil uncorrected gravity was 1.018. I haven't had one zoo far off before it is a little disconcerting!:cross:

 

[Kegger320]

I would consider 1 gravity point off a success! As for accuracy at high temps, just make sure the calculator you are using has incorporated that temp in its range. For example, http://www.brewersfriend.com/hydrometer-temp/ goes up to 159 so you can't use it higher than that. If you really want to quickly and accurately measure wort at different points through the lauter, invest in a refractometer.

I appreciate that website, it shows the same temp corrections, so hopefully I'll be close.

I haven't ever used a refractometer before, how does it work? I'm always up for buying a new brewtoy!

 

[HungusBrews]

I haven't ever used a refractometer before, how does it work? I'm always up for buying a new brewtoy!

It is fairly simple. You just put a few drops of wort on the lens and hold it up to the light to take a reading. You will want to find one that has a scale for SG so you don't have to convert from Plato or Brix. The drops cool instantly which allows for a more accurate reading.

 

[Kegger320]

It is fairly simple. You just put a few drops of wort on the lens and hold it up to the light to take a reading. You will want to find one that has a scale for SG so you don't have to convert from Plato or Brix. The drops cool instantly which allows for a more accurate reading.

That sounds great, do have a brand you prefer?

 

[peterj]

If the corrected temp(from Beersmith at 156*f) is correct i was within .003 of the recipe. If the corrected temperature was wrong I was nowhere close as my pre-boil uncorrected gravity was 1.018. I haven't had one zoo far off before it is a little disconcerting!:cross:

Well just because the corrected gravity may not be exactly right, that doesn't mean the uncorrected gravity of 1.018 is right. 1.018 is definitely NOT correct. The only question is how far off is the corrected gravity reading. But again, I wouldn't worry too much because it's probably not too far off of that.

 

[HungusBrews]

That sounds great, do have a brand you prefer?

I think I have this cheap one from ebay http://www.ebay.com/itm/like/370884270385?lpid=82

I would recommend finding one that is a little more beefy. This one seems to need a calibration every time I brew. Its a very simply process but just one more step to worry about.

 

[Kegger320]

I think I have this cheap one from ebay http://www.ebay.com/itm/like/370884270385?lpid=82

I would recommend finding one that is a little more beefy. This one seems to need a calibration every time I brew. Its a very simply process but just one more step to worry about.

Thanks gentlemen, I just ordered a refractometer. They were more reasonable in price than I expected.

Oh well, there goes one more excuse if my beer turns out crappy.

 

[theashman661]

I appreciate that website, it shows the same temp corrections, so hopefully I'll be close.

I haven't ever used a refractometer before, how does it work? I'm always up for buying a new brewtoy!

They are around $15- . Great investment. You can sample hot wort with only a drop or two of fluid. This is great so your not wasting so much beer as you would a hydrometer. But the only down fall, is once the beer is fermenter, there is alcohol in the samples you take. This throws off the reading, but can be compensated by a correction calculator.... I have forgotten about this almost every time a brew. I get all scared and for a second I wonder why my gravity is so high! then I remember the correction calc. Make the changes and boom I'm at my target FG. You will need some distilled water to calibrate it to 1.000. Then your ready to rock and roll! I got mine off ebay. Be sure to look for a brews refract. I got one the first time around and it was for machine oil or something. Didn't work for brewing, had to re-sell on ebay.

 

[Kegger320]

Well, I solved the low gravity mystery. My digital thermometer was reading 15* high, so in actuality I was mashing around 138 ish. Oh, we'll at least it is still beer. I found out the thermometer was off on my next batch, so now I probably have two bad batches, but at least the mystery is solved.

I just want to that everyone for their spot on advice and encouragement. This @&$@ is addictive!!

 

[Kegger320]

I appreciate that website, it shows the same temp corrections, so hopefully I'll be close.

I haven't ever used a refractometer before, how does it work? I'm always up for buying a new brewtoy!

Buy the way HungusBrews, I loved my new refractometer, what a breeze. That was awesome.