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**blakelyc** · 05-16-2012, 01:26 AM

Hi folks! I have a hydrometer, and I used it religiously to test for completion (engineer here, on the anal retentive side of the brewing continuum).

That having been said, I also hate it. Too much volume, the thief is a pain, etc. is the refractometer correction (for alcohol) really that unreliable? I was thinking today that switching to a refractometer and pulling small volumes with pre-sterilized disposable pipettes would be awesome.

I just don't understand the refractometer drawbacks. Anyone want to fill in this information? Does the correction change more with larger OG-to-FG differences? I saw a site with some math, but that was just a curve fit against hydrometer data. Is there a non-empirical formula?

-b

lumpher · 05-16-2012, 01:37 AM

the addition of alcohol throws off the refractometer to a level where it's completely inaccurate. it's good for pre-fermentation, but not for final gravity

**HopSong** · 05-16-2012, 01:47 AM

refractometer for brewday.. don't have to cool off a bunch of wort to get a reading to see if you are in the proper range. Later.. use it for your OG/SG

Hydrometer for later. You can certainly wait for 10 days to take the first hydrometer reading. Four days later for another. and another 3-4 for your final gravity reading.. for normal beers.. High Grav brews will likely need more days for both the first one or two later readings.

I don't sweat it.. I leave my brew in the FV for about 15 days before my first hydrometer reading. Another 5 days for the 2nd. If I have questions, I'll take a third.. but, this is less than a 12 oz bottle of beer.. and I drink all of them. It's a good way to try to pick up on the slight differences in the brew as it progresses.

pennztatelion · 05-16-2012, 01:48 AM

Quote:

Originally Posted by lumpher

the addition of alcohol throws off the refractometer to a level where it's completely inaccurate. it's good for pre-fermentation, but not for final gravity

Although there is a good spreadsheet I've seen around to compensate for the alcohol content when using a refractometer for during and final refractometer readings. I know it's on the morebeer.com site.

**HopSong** · 05-16-2012, 01:51 AM

Also, Morebeer sells a refractometer that has been calibrated to work with beer.. ie "wort" that has some level of alcohol in it. I have no idea how accurate it is... but, they say they put a lot of effort working with the mfg to design a meter that works.

**Golddiggie** · 05-16-2012, 01:57 AM

The mentioned spreadsheet does compensate for the presence of alcohol to make the readings valid. I used it on the batch I kegged last and it matched the estimated FG on the brew. I plan on confirming another brew (the one in process now) to see how close it really is. I have a feeling that it's close enough to not matter for us.

Personally, if it's a SG point (or two) off it's not the end of the world. The batch won't be ruined or enjoyed any less because of it. The advantages of using the refractometer more than offset any potential negatives. Such as needing just a couple of ml to get a reading. Even that's more than you actually need. I typically use a 4 dram vial to reserve a sample for testing (OG and now FG). So that's 1/2oz in each vial reserved for readings. MUCH less than what you typically pull for a hydrometer sample.

I have two refractometers now. One from Bobby_M for beer and another that is a higher scale to test things like honey and maple syrup with (goes up to 80 brix). I look forward to testing some honey with the new refractometer to see what it's sugar content level really is.

**Golddiggie** · 05-16-2012, 02:01 AM

Quote:

Originally Posted by HbgBill

Also, Morebeer sells a refractometer that has been calibrated to work with beer.. ie "wort" that has some level of alcohol in it. I have no idea how accurate it is... but, they say they put a lot of effort working with the mfg to design a meter that works.

From their site...

Now Take Readings During or After Fermentation
In the past you could only use a refractometer during the brewing process, before the presence of alcohol. Once alcohol was present the reading was distorted and innacurate. Our free downloadable excel spreadsheet, and included how-to use video, now compensates for the presence of alcohol allowing you to use a refractometer from the start of the brewing process all the way to the finish of fermentation.

So, the refractometer has NOT been changed, they just tell you to use the spreadsheet...

**blakelyc** · 05-16-2012, 02:11 AM

A refractometer could, then, be used during fermentation to figure out if the gravity isn't changing...... Even if the gravity reading is inaccurate, it is still precise enough to detect fluctuations near the end of fermentation. Right?

I certainly don't mind using the hydrometer at bottling time because I already have fluid moving around... But I do lots of 1-gallon test batches, meads, etc., for which filling up my hydrometer sample jar is a fair loss of volume. I don't worry about fermentation, but I am a data-driven guy, so I like to test.

**Golddiggie** · 05-16-2012, 02:15 AM

Just use the spreadsheet, or other software, to 'translate' the refractometer readings (once alcohol is present) to true readings.

Personally, I don't take any readings once I pitch the yeast. For beers at least. In my initial mead batches I was taking readings until I hit the 1/3 break. This time around I just left them along, making sure I gave enough nutrient at the start for the yeast (it's another method, fully valid).
Still, for a beer, I'll take the OG, then a FG reading (so that I know what I ended up with). Less times going into the batch means less chance of something going sideways on me.

**helibrewer** · 05-16-2012, 03:14 AM

My refractometer and hydrometer differ by about .002 at FG so I just go by the refractometer....if the value makes sense all I care about is that it's not changing any more...I will take a hydrometer on occasion during the cold crash period to satisfy curiousity, but not often.