Refractometer post fermentation correction formula

Does anyone know where to find it? I understand there are online resources, but I'd like to take a shot at adding this feature to my brew day spreadsheet.

I use my phone, I dono if this helps?
https://play.google.com/store/apps/details?id=com.BrewBuddy

The best calculator for translating post ferment Brix readings to gravity readings that I have found is produced by Sean Terrill.
See http://seanterrill.com/2011/04/07/refractometer-fg-results/ for details. He even provides spreadsheet templates for your convenience.
Personally, if there's any doubt, I take Brix readings to determine when fermentation is finished, and then take a single gravity reading with an hydrometer to determine what the final gravity is, and to judge the taste of the sample.

-a.

ajf said:

The best calculator for translating post ferment Brix readings to gravity readings that I have found is produced by Sean Terrill.
See http://seanterrill.com/2011/04/07/refractometer-fg-results/ for details. He even provides spreadsheet templates for your convenience.
Personally, if there's any doubt, I take Brix readings to determine when fermentation is finished, and then take a single gravity reading with an hydrometer to determine what the final gravity is, and to judge the taste of the sample.

-a.

Click to expand...

This. The Sean Terrill calculator is the best I've found and he shows all of his math/calculations.

I recommend doing your own comparisons. When you collect enough data you will have a correction factor that you can plug into your software.

Got the spreadsheet, will do my own comparisons. One of the reasons I do 4 weeks primary is to ensure the beer fully attenuates. Don't want to take the loss of a cylinder of wort daily. Hoping that with the smaller sample needed for a refractometer, I can take more frequent samples.

A point of edification; Why is Brix used in the calculators as opposed to SG? I have a dual scale refractometer, so I can use either. Just wondering.

Most refractometers only have a Brix scale. If they have an SG scale as well, that is usually calibrated for simple sugar or fruit juice solutions, and is not going to be completely accurate for wort.

When I'm waiting for a brew to reach FG, I take a refractometer reading about once every 4 days, but don't bother to convert to SG. When I get two identical readings, 4 days apart, then I take an hydrometer sample to see what the FG really is. I tried using the refractometer and a calculator many years ago, but the results were not accurate.

-a.

ajf said:

The best calculator for translating post ferment Brix readings to gravity readings that I have found is produced by Sean Terrill.
See http://seanterrill.com/2011/04/07/refractometer-fg-results/ for details. He even provides spreadsheet templates for your convenience.
Personally, if there's any doubt, I take Brix readings to determine when fermentation is finished, and then take a single gravity reading with an hydrometer to determine what the final gravity is, and to judge the taste of the sample.

-a.

Click to expand...

Yes this is the one which has proven accurate for me. I actually tested it with hydrometer.

It looks like Sean's is based on a large set of experiment data. Others I have seen seem to be based on the Balling observation or analytics.

Each tool has its place. Refrctometers are good at measuring refraction index. Hydrometers are good at measuring relative density. Neither are great at measuring final sugar or alcohol content because assumptions need to be made defining what "normal" fermentation is in order to use them. However, armed with both tools you can achieve more accurate measurements of alcohol and residual sugar.

william_shakes_beer said:

Got the spreadsheet, will do my own comparisons. One of the reasons I do 4 weeks primary is to ensure the beer fully attenuates. Don't want to take the loss of a cylinder of wort daily. Hoping that with the smaller sample needed for a refractometer, I can take more frequent samples.

A point of edification; Why is Brix used in the calculators as opposed to SG? I have a dual scale refractometer, so I can use either. Just wondering.

Click to expand...

Brix/degrees Plato were originally used for wine making, they continue to use that scale rather than SG/density (vs refraction index). Wine is a simpler, more sugar/water only mixture than wort if I understand it correctly.

I think the original cubic equation that Sean refers to and that most brewing software uses was actually developed based on wine fermentation. Cool to see this but I was wondering, would the color of the beer have any effect on the accuracy of the correction?

From reading Sean's blog I though he did a fit on twelve data points that he collected with some friends.

I wouldn't expect color to skew a refractometer much. The blue color of the prison limits the light color, and blue is a very easy color for the eye to see. Over the entire visible light range the index of refraction changes by 0.01. Over the blue range it is much smaller. Each degree Brix corresponds to a change of about 0.02 index of refraction.