Anyone else use Sean Terril's Refractometer Calculator?

Systems, Gear, & DIY
1

I’m a bit frustrated over differences in ways people convert refractometer readings to specific gravity.

I have a pre-fermentation reading of 12.9 brix which beersmith converted to 1.053 SG.
http://www.fermsoft.com/gravbrix.php lists 12.85 brix as 1.052, so its pretty close to beersmith.

Now I’m trying to use Sean Terril’s site to convert a post-ferment brix reading into a final gravity.

I enter:
Original RI (°Bx): 12.9
Final RI (°Bx): 6.4

And it gives me this for results:
Original Gravity: 1.0501 (12.4°P)
Estimated Final Gravity: 1.0118 (3.01°P)
Alcohol by Volume: 4.9% (4% ABW)

Sooo…is 12.9 brix 1.050 or 1.053? I’m confused.  :-[ It looks like he divides the brix number by 1.04 to get degrees plato. I think I may have screwed up my configuration in Beersmith as it requires you to calibrate your refractometer…which I sort of fudged… So this may be all my fault.

2

I use it. Its always the same as Beersmith for OG.

I dont have my config settings on me right now. I will check when I get home on my config settings!

3

12.9°Bx is 1.0522 (SG 20/20°C). A refractometer reading of 12.9°Bx in wort corresponds to an SG of about 1.049-1.051, depending on the wort correction factor.

This came up in a thread a few days ago: http://www.homebrewersassociation.org/forum/index.php?topic=11513.msg144017#msg144017

You’ll have to scroll down until someone fixes the anchored URLs. Fifth post from the bottom.

4

I’m making a starter this weekend so I’ll use that as an opportunity to double check everything and fix my calibration in beersmith. I’m not sure where I got the numbers I put in there but my correction factor was something like 0.99.  When I put in some values that give me a correction closer to 1.04 then beersmith matches Sean’s site for OG.

5

Pre-fermentation, any calculator should give the same result as long as the wort correction factor is the same.

Post-fermentation, there’s no comparison. My calculator’s right, and everyone else’s is wrong. ;D

6

Hehe, I just noticed who you were…I’m slow that way!  ;D

Yeah, I was using yours for post-fermentation…thanks for the site!

All of my confusion was due to the screwed up value I have in beersmith for the correction factor. Live and learn!