First Time Reading Refractometer

[smata67]

I got one of those cheap ATC models. My hydrometer gives me a 1.003 FG reading (adjusted for temperature, wort is at 68F). Refractometer is giving me 1.022. OG on this was 1.067. So ABV is about 8.4%. I mashed this lot at too low a temperature due to a measurement flub up with a corresponding high attenuation. So, going forward, I adjust all of my refractometer readings by multiplying by 1.003/1.022 or .98?

 

[dmtaylor]

Ignore the SG scale on your refractometer. Use only Brix readings with the following calculator. That's all you need to do, then it will read right.

https://www.brewersfriend.com/refractometer-calculator/

Cheers.

 

[smata67]

I did that and the 5.6 Brix reading corresponded to the 1.022 SG. But beer is definitely 1.003, I can't see straight after one bottle.

 

[rburrelli]

Refractometers do not read correctly in the presence of alcohol. Ther is an adjustment factor that needs to be applied. I believe it is shown on that Brewersfriend link someone else supplied.

 

[deadwolfbones]

Yep, you just plug in the OG in Brix and the FG in Brix and it'll give you the actual FG in hydrometer numbers.

 

[deadwolfbones]

Something is still fishy with your readings, though:

 

[dmtaylor]

I did that and the 5.6 Brix reading corresponded to the 1.022 SG. But beer is definitely 1.003, I can't see straight after one bottle.

You're doing it wrong. It should look something more like this:

 

[smata67]

Attached are my readings. Is my problem here that I need to take the actual refractometer OG reading to calculate the wort correction and not the hydrometer OG? I did not have the refractometer back then. Still, seems odd that I read off 1.022 with the refractometer and my actual FG is 1.003.

 

[dmtaylor]

Attached are my readings. Is my problem here that I need to take the actual refractometer OG reading to calculate the wort correction and not the hydrometer OG? I did not have the refractometer back then. Still, seems odd that I read off 1.022 with the refractometer and my actual FG is 1.003.

You need to use both refractometer and hydrometer together for a few batches to establish your wort correction factor in Part I. A factor of 0.85 is very unusual, very low -- typically this will be around 0.95 to 1.05 or very close to 1.00 on average.

Then in Part II, you should only be using Brix values with your wort correction factor (whatever that ends up being). Then everything will work out great.

Since you didn't have your refractometer originally on this batch, and don't yet know your wort correction factor, it's really hard to try to figure out what the original Brix must have been and get these to match. But now if you follow my advice here which is same as on the BF website, then you should be good on future batches.

Cheers.

 

[smata67]

Silly me thinking I could just read the proper value off the refractometer. I'll take some OG readings next batch and go from there. Still a bit wanky about the FG value showing 1.022 when it is actually substantially different, though.

 

[RM-MN]

Still, seems odd that I read off 1.022 with the refractometer and my actual FG is 1.003.

Not a bit odd. The refractometer works well for your pre-boil and OG because those samples do not contain alcohol yet. One alcohol is present it changes the refractive index and your refractometer reading then needs some correction factor. If you "need" to know the exact FG, you use the hydrometer. If you just want to see that fermentation is complete, the refractometer will work for that as you are looking for exact measurements over a couple days time.

 

[dmtaylor]

Silly me thinking I could just read the proper value off the refractometer. I'll take some OG readings next batch and go from there. Still a bit wanky about the FG value showing 1.022 when it is actually substantially different, though.

Yeah..... you missed the part about alcohol effing up the reading. High Brix readings at the end is normal, and is precisely why you MUST use the BF calculator or equivalent to calculate the actual result.