[bluesman]

I use my refractometer pre-fermentation and stick to the hydrometer for post fermentation.

+1

This is my practice as well.

[euge]

I use my refractometer pre-fermentation and stick to the hydrometer for post fermentation.

+1

This is my practice as well.

Mine too.

Get the refractometer with ATC. Invaluable.

[a10t2]

While this is true, in my experience none of the existing spreadsheets or conversion factors for post fermentation refractometer readings are very accurate.  They are sometimes off by more than 4 points from what my hydrometer reads.

Does "conversion factors" plural mean you've tried mine out and it didn't work for you? As far as I know every other tool uses the same formula.

[Tim McManus]

If you're calculating %alcohol in the finished beer, a hydrometer is the way to go.  Yes, you can use a refractometer but there is a bit of math involved, whereas if you use a hydrometer, it's the difference between the pre-fermentation gravity and the post-fermentation gravity.

If you want to take gravity readings through the mash and boil, then a refractometer is more practical.

[Beer Monger]

OK.  Thanks guys.  I've got a decision to make.....

[glastctbrew]

While this is true, in my experience none of the existing spreadsheets or conversion factors for post fermentation refractometer readings are very accurate.  They are sometimes off by more than 4 points from what my hydrometer reads.

Does "conversion factors" plural mean you've tried mine out and it didn't work for you? As far as I know every other tool uses the same formula.

+1 to Sean's "conversion factors".  I modified the morebeer spreadsheet with his formulas and have found the post fermentation results to be with in a point of the hydrometer reading.  I'm pretty much at the point where I use the hydrometer because I have too much beer to rack into a keg and not enough to fill a bottle.  I'll grab a hydrometer reading before I drink it for s***s and giggles.

[Beer Monger]

While this is true, in my experience none of the existing spreadsheets or conversion factors for post fermentation refractometer readings are very accurate.  They are sometimes off by more than 4 points from what my hydrometer reads.

Does "conversion factors" plural mean you've tried mine out and it didn't work for you? As far as I know every other tool uses the same formula.

+1 to Sean's "conversion factors".  I modified the morebeer spreadsheet with his formulas and have found the post fermentation results to be with in a point of the hydrometer reading.  I'm pretty much at the point where I use the hydrometer because I have too much beer to rack into a keg and not enough to fill a bottle.  I'll grab a hydrometer reading before I drink it for s***s and giggles.

I always drink my hydrometer samples too.  It gives me at least a basic idea of where things are at taste-wise. 

[tschmidlin]

While this is true, in my experience none of the existing spreadsheets or conversion factors for post fermentation refractometer readings are very accurate.  They are sometimes off by more than 4 points from what my hydrometer reads.

Does "conversion factors" plural mean you've tried mine out and it didn't work for you? As far as I know every other tool uses the same formula.

I tried yours for a batch or two but it gave me similar numbers as the morebeer spreadsheet.  I'll test it again on my latest batch, I haven't bothered to get a refractometer reading from it post fermentation but I have the rest of the numbers already so it will be easy.  I'll report back.

Based on glastctbrew's post maybe I'm doing something wrong, I'll check that too.

[denny]

Which comes back to my original question.  If I'm getting the info I need from my hydrometer, do I really need/is it really worth getting a refractometer?  I have other things I could use the $$ for. 

When I brew, I boil to gravity, not volume.  The refractometer made it easy to get a really quick reading to see where I stood.  Now that I'm not using it, I pull a kettle sample (6-8 oz.) with a Pyrex measuring cup and put it in a metal cocktail shaker.  I put that in a bowl of ice water and swirl it around.  In about 2 minutes, it's cooled down enough to read.  Not quite as fast as a refractometer, but good enough.

[Beer Monger]

Which comes back to my original question.  If I'm getting the info I need from my hydrometer, do I really need/is it really worth getting a refractometer?  I have other things I could use the $$ for. 

When I brew, I boil to gravity, not volume.  The refractometer made it easy to get a really quick reading to see where I stood.  Now that I'm not using it, I pull a kettle sample (6-8 oz.) with a Pyrex measuring cup and put it in a metal cocktail shaker.  I put that in a bowl of ice water and swirl it around.  In about 2 minutes, it's cooled down enough to read.  Not quite as fast as a refractometer, but good enough.

If you're boiling to gravity, however, doesn't that mean you have to adjust the boil time as you go to account for evaporation until you hit your target? 

How big an effect doe that have on the bittering hops or other factors?

I usually boil a timed boil - and hope I hit my volume.  I'm not as concerned w/ having my beer be the exact alc. % I was shooting for. 

[denny]

If you're boiling to gravity, however, doesn't that mean you have to adjust the boil time as you go to account for evaporation until you hit your target? 

How big an effect doe that have on the bittering hops or other factors?

There is so little utilization from bittering hops beyond 60 min. that it really doesn't matter.  For later additions, the gravity reading is crucial to make sure I'm on track and that my 10 min. hops don't turn into 30 min. hops while I wait for the wort to boil down.

I usually boil a timed boil - and hope I hit my volume.  I'm not as concerned w/ having my beer be the exact alc. % I was shooting for. 

I'm not as concerned about ABV as I am with making sure that my BU:GU ratio ends up where I want it to so that the flavor of the beer isn't impacted.  So I want to be sure I hit my predicted OG as closely as possible.

[tschmidlin]

I tried yours for a batch or two but it gave me similar numbers as the morebeer spreadsheet.  I'll test it again on my latest batch, I haven't bothered to get a refractometer reading from it post fermentation but I have the rest of the numbers already so it will be easy.  I'll report back.

Based on glastctbrew's post maybe I'm doing something wrong, I'll check that too.

Ok, here's what I've got.  Two carboys with OG 25.5 brix (1.106 according to beersmith, not confirmed with a hydrometer)

Refractometer readings A - 13 and B -12.8 brix.

The different spreadsheets say:

Sean's: A - 1.0194
           B - 1.0172
  Notes: There are two different equations in column E for calculating OG from the refractometer reading. version 2.1.  One row says 1.106, the rest say 1.107.  I used 1.107 for these numbers.  The numbers reported are from the "new" column.

morebeer: A - 1.019
               B - 1.018
  Notes: Spreadsheet calculates OG as 1.108

Beersmith: A - 1.019
                B - 1.018
  Notes: I'm using the default correction factors, used 1.106 as the OG because that is what beersmith calculates from 25.5 brix.

FG readings with my hydrometer (I double checked calibration) 1.025 and 1.024 after adjusted for temperature.  None of them come that close, off by about 5 points across the board.  This is similar to what I saw before.

It's possible there is some user error when I wrote down the OG since I usually don't write it down right away and I'm sure I didn't check the temperature of the sample (cooled sample, ATC refractometer).  Then again this is the same I saw before.  I really do want to do some better controlled experiments some time.

[bluesman]

FG readings with my hydrometer (I double checked calibration) 1.025 and 1.024 after adjusted for temperature.  None of them come that close, off by about 5 points across the board.  This is similar to what I saw before.

It's possible there is some user error when I wrote down the OG since I usually don't write it down right away and I'm sure I didn't check the temperature of the sample (cooled sample, ATC refractometer).  Then again this is the same I saw before.  I really do want to do some better controlled experiments some time.

Interesting data Tom. I may also revisit this someday. I also found it difficult to get consistent readings after error correction between my refractometer and hydrometer post fermentation. I have been using my hydrometer mostly because I can trust it but also because I can sample the final product which is important to me. The jury is still out on this one. 

[ccarlson]

I love my refractometer and it's always within a point or 2 of my hydrometer. If the wort is very hot, be sure and let the sample sit for about 20 seconds, before taking a reading. I find this to be much more accurate. .

[bluesman]

I love my refractometer and it's always within a point or 2 of my hydrometer. If the wort is very hot, be sure and let the sample sit for about 20 seconds, before taking a reading. I find this to be much more accurate. .

Me too. I usually allow the hot wort to sit on the prism with the plastic cover closed for about 15 seconds to cool before taking a reading.