Ergh. Broken Hydrometer - adjusting for alcohol with Brix FG reading

[pat86]

Hey guys, same old story - I broke my hydrometer and can't seem to get a reasonable answer on what my FG is from my refractometer...

BUT wait... here is the dumb part - I have actually been trying to adjust the reading for the presence of alcohol, but all of the calculations don't make sense.

Here we go:

Starting gravity:

15.8 BRIX (1.065 S.G.) - This is pretty much right on for the recipe so I believe it

Final Gravity: 5.8 BRIX - measured several times with refractometer in the sunlight at bottling and a couple of times with some flat beer.

Calculators are telling me I have a final gravity of .997 or 1.007 which is whack.

I used a big US05 cake, with the recipe we were targeting about 1.016 for the FG and it tastes about 1012-1016. In a smaller beer with a lower mash, etc. I usually won't get US05 down past 1.009 so no way this is right.

I've tried a few ABV correction calcs like this and this but must be doing something wrong... Do I need to re-calibrate the refrac? Am I using the calcs wrong.

The beer tastes good so I'm fine, but it is annoying me hugely!

 

[danestead]

Yeh there is something wrong with either your OG or FG readings.

To begin with, make sure its reading 0 brix with some water on it. Distilled or Reverse osmosis water would be best for that.

You can also check the calibration at different brix readings if you have some accurate scales. 1g accuracy would be the minimum with 10ths of grams even better.

Measure 90g of distilled water (or reverse osmosis if you dont have distilled. Tap water may work close enough however that is a guess). Mix in 10g of table sugar (sucrose). You will now have 100g total solution. This is the equivalent of 10 plato or for your brix refractometer it should read pretty much 10.4.

Edit: On 2nd thoughts, you may as well check the calibration at closer to your OG of 1.065. Use 84g of water and 16g of sugar. That should be 16.64 Brix.

 

[huez]

You should be calibrating you refractometer every day you use it really, this is probably where you are getting an error in the calculation. Do what danestead suggested, calibrating with a known sample is better than using distilled water.

 

[danestead]

Yeh there is something wrong with either your OG or FG readings.

To begin with, make sure its reading 0 brix with some water on it. Distilled or Reverse osmosis water would be best for that.

You can also check the calibration at different brix readings if you have some accurate scales. 1g accuracy would be the minimum with 10ths of grams even better.

Measure 90g of distilled water (or reverse osmosis if you dont have distilled. Tap water may work close enough however that is a guess). Mix in 10g of table sugar (sucrose). You will now have 100g total solution. This is the equivalent of 10 plato or for your brix refractometer it should read pretty much 10.0 brix. With a sucrose solution, plato = brix.

Edit: On 2nd thoughts, you may as well check the calibration at closer to your OG of 1.065. Use 84g of water and 16g of sugar. That should be 16.0 Brix.

I just realised I applied the wort correction factor of 1.040 which isn't needed when calibrating with a sucrose solution. I'm unable to correct the original post however I've corrected the bold values in the quote as part of this post.

 

[danestead]

Hey guys, same old story - I broke my hydrometer and can't seem to get a reasonable answer on what my FG is from my refractometer...

BUT wait... here is the dumb part - I have actually been trying to adjust the reading for the presence of alcohol, but all of the calculations don't make sense.

Here we go:

Starting gravity:

15.8 BRIX (1.065 S.G.) - This is pretty much right on for the recipe so I believe it

Final Gravity: 5.8 BRIX - measured several times with refractometer in the sunlight at bottling and a couple of times with some flat beer.

Calculators are telling me I have a final gravity of .997 or 1.007 which is whack.

I used a big US05 cake, with the recipe we were targeting about 1.016 for the FG and it tastes about 1012-1016. In a smaller beer with a lower mash, etc. I usually won't get US05 down past 1.009 so no way this is right.

I've tried a few ABV correction calcs like this and this but must be doing something wrong... Do I need to re-calibrate the refrac? Am I using the calcs wrong.

The beer tastes good so I'm fine, but it is annoying me hugely!

You've gone quiet. Did u get it sorted?

 

[btrots87]

I agree that 0.997 sounds ridiculous and I would stop using that calculator, however I've been using the brewers friend calculator that you got the 1.007 reading from and comparing it with my hydrometer reading, and so far it has been quite accurate. Although almost 90 percent attenuation seems pretty high for US05.

For the purpose of calculating alcohol I would just assume that 1.007 is correct, better to be conservative than underestimate how many standard drinks you've had, especially if driving.

 

[pat86]

Hey guys thanks for the replies - have been away for a few days, will have to mix up a sugar solution and re-calibrate this week. Will let you guys know how it goes!