Refractometer questions

[njohnsoncs]

I mostly brew 2.5-3 gallon batches via BIAB. Right now I use a hydrometer to measure my OG/FG but I don't like how much beer it wastes. I'd like to buy a refractometer and start using that. I have a couple questions regarding refractometers:

1. Can you take a drop of wort right after the mash and use the refractometer to measure SG? I want to see if I'm hitting my numbes preboil. With a hydrometer, I have to put it in the freezer to get the temp down in order to get an accurate measurement. Do I need to do the same with a refractometer?

2. Can I use it to measure FG? I've heard a refractometer doesn't work after fermentation because of the ethanol and a correction needs to be made. How accurate is the correction?

3. Is a refractometer more accurate (or reliable/consistent) than a hydrometer?

Thanks!

 

[enkamania]

1. Since it such a small sample, it cools down in seconds
2. There are correction factors, I always used the hydrometer for this
3. I thought it was good pre boil, wouldn't use it for FG

 

[auburntsts]

1. Yes, but best to cool it first. Mine came with a plastic pipette. I just pipe a little bit into a small sauce cup (like you'd use for soy sauce or similar) and in a couple of minutes it's cooled to room temp at which point I put a few drops on the refractometer and take the reading.

2. Yes, but you have to use a calculator to compensate for the alcohol: Http://seanterrill.com/2012/01/06/refractometer-calculator/

It's not perfect but close enough

3. No, but it's easier to use IMO.

 

[ancientmariner52]

1. I use little plastic coffee stirrers as disposable pipettes. A single drop is enough, it cools almost instantly on the refractometer platen. Be sure to stir before sampling if you want good results.

2. I use the refractometer to determine when fermentation is finished, because of the tiny sample. It's like a speedometer that you know is inaccurate. It will tell you if you are slowing down or holding a steady speed, but not your actual speed.

3. When the refractometer tells me fermentation is finished, I take a hydrometer sample for the actual FG. Obviously, since I use two different instruments for OG and FG, there will be slight errors in the ABV result. But I pretty much don't care.

 

[kh54s10]

1) Yes, My refractometer is an ATC model so it is supposed to correct automatically for temperature. But the tiny amount of wort cools very quickly anyway. I take a reading after the mash, after my first batch sparge and after the second (preboil). Then after the boil I get my OG.

2) You can use it for FG but you do need to make a correction. There are online calculators, how accurate they are is up for debate. I don't use my refractometer for FG.

3) No, I don't think mine is anyway. There are different scale hydrometers and probably refractometers also. The scales on mind are such that you have to make a bit of an estimation when making the reading.

Make sure you check the calibration of the refractometer and adjust if necessary. I do this at the start of every brew session and sometimes again during.

 

[doug293cz]

Be careful when pulling small, hot samples. If the sample has a lot of exposed surface area, a significant amount of water can evaporate before you get the reading taken. This will cause your SG reading to be higher than the SG of the bulk wort. I take a small sample in an eyedropper, let it cool a bit in the dropper, then place a couple of drops on the refract plate. Not much evap can occur thru the tiny opening in the tip of the dropper.

Brew on

 

[BrewnWKopperKat]

I mostly brew 2.5-3 gallon batches via BIAB. Right now I use a hydrometer to measure my OG/FG but I don't like how much beer it wastes. I'd like to buy a refractometer and start using that.

The AHA forums had a long (and long running) post on refractometer corrections: https://www.homebrewersassociation.org/forum/index.php?topic=28544.0

Currently, I use a refractomenter for OG measurements. I take FG measurements with a hydrometer. I also scale my batch sizes for a desired number of bottles + volume for FG hydrometer readings. My thought is that the beer for the FG reading is a "cost of doing business".

 

[schematix]

Even with the corrections it's only going to be accurate to a few points at best. Up to you if that's good enough.

 

[azmark]

If you use the correction app on Brewers Friend, you'll be pretty close on FG for most modest gravity beers. Beers starting over 1.070 may be further off. Even so, you'll be close. Your hydrometer and your ability to read it may be off by just as much. You'll be able to see if fermentation has stopped with the refractometer, by taking 2-3 readings over a few days to see if it has stopped. If near your projected final gravity, call it good. (if doing high gravity beers and bottling, use a hydrometer)

 

[GPP33]

FG hydrometer samples are not waste, they are your chance to sample your delicious brew. Please tell me you don’t dump them...