Brix and SG don't match

[Jay204]

First time using a refractometer throughout fermentation. Prior to pitching yeast my Zinfandel was at 24.5 brix. 5 days into fermentation it shows a reading of 6.5. If I use the brix calculator form MoreWine to account for the alcohol, that would suggest my brix is -5.6, which isn't possible.

I tested SG and came up with a reading of 0.998, which would be 9.65 brix. Why is my brix off by so much?

(My refractometer has ATC and reads a perfect 0 brix with a drop of water)

 

[Ajmassa]

Bad maths methinks. Calculator spitting out wrong figures. Trust the SG. Once fermentation is started I discard the refractometer anyway. Walking 10mi. to get 1.
Starting 24.5% Brix°
.998 SG finish.
Cut and print

And check out FermCalc. The gold standard of wine calcs. You name it-it does it.
http://www.fermcalc.com/FermCalcJS.html

 

[stickman]

The morewine spread sheet indicates your actual specific gravity is .979 based on the refractometer numbers you provided. Your looking at the wrong column.

 

[Jay204]

The morewine spread sheet indicates your actual specific gravity is .979 based on the refractometer numbers you provided. Your looking at the wrong column.

The MoreWine spreadsheet appears to find the actual specific gravity by converting the observed brix and accounting for alcohol content, then it simply converts the SG number back to brix to find actual. So 0.979 is the same as -5.6 brix. Either way, 0.979 isn't even possible, is it? and it certainly doesn't match the 0.998 reading I got when I used a hydrometer.

I guess my real question is whether or not people find the conversion chart reasonably accurate when using their refractometer after fermentation has started. I'm only really using it as a daily check to see if sugar is still being depleted.

 

[stickman]

There are all kinds of calculators on the net, you just need to find a good one that works for you, many of them have correction factors that need to be applied or even tweaked. This one indicates .991 using the default 1.04 correction factor. https://www.petedrinks.com/abv-calculator-refractometer-hydrometer/

Personally I use a hydrometer, but during fermentation even with a hydrometer you need to take the reading quickly or bubbles collect on it and give a false high reading. I just use the hydrometer as a quick indicator of what's going on, no precise calculations going on here.

 

[G259]

Regarding fermcalc, i can't say enough good things about it. Put in must SG, and it tells you how much sugar to add for a specific SG final. It is always spot on!

 

[salcoco]

the refractometer correction spreadsheet may have errors once the end of fermentation is reached. it is a good tool for monitoring fermentation progress as it only takes one drop to measure status. once the fermentation is complete I think it gets a little erroneous. use a hydrometer to measure final sg.

 

[Jay204]

the refractometer correction spreadsheet may have errors once the end of fermentation is reached. it is a good tool for monitoring fermentation progress as it only takes one drop to measure status. once the fermentation is complete I think it gets a little erroneous. use a hydrometer to measure final sg.

Yea that's what I did. Refractometer spreadsheet wasn't accurate at all. Tested all musts with a hydrometer and got 0.994-0.996 for all of them. Pressed last night.

 

[sjjan]

I am also having some trouble using a refractor instead of hydrometer during fermentation. It would be cool to be able to use my digital refractormeter instead of the hydrometer.

 

[salcoco]

- ValleyVintner Main Page this will have a spreadsheet that corrects refractometer reading to sg. it gets risky at low levels around sg=1.000 but works great to monitor fermentation to that point. with experience you will determine that fermentation stops at about 5-8 brix on the refractometer and then you can measure with a hydrometer to verify.

 

[sjjan]

- ValleyVintner Main Page this will have a spreadsheet that corrects refractometer reading to sg. it gets risky at low levels around sg=1.000 but works great to monitor fermentation to that point. with experience you will determine that fermentation stops at about 5-8 brix on the refractometer and then you can measure with a hydrometer to verify.

I had found that ValleyVintner page already on my iPad but downloading the Excel sheet from my iPad would result in errors telling me the .xls file was locked. Now I tried it on my MacBook Pro and there it works fine. Thanks! I did have to replicate the information in a separate spreadsheet as parts of the Excel sheet seems to be locked or password protected. The sheet - as is - is not good for me as we work here in Europe with Oechsle instead of Brix and Celsius instead of Fahrenheit. I now have a file that I can work with. Great to be freed for most of the fermentation of the hydrometer.

 

[sjjan]

So, the starting Brix value was 21.1 as measured with a digital refractormeter. The current Brix valuse (observed, AB) is 13.5 which results in an adjusted SG of 1034. Using a hydrometer, I observe a SG of 1048. Why the huge difference? Any idea?

 

[Rice_Guy]

The refractometer will measure the change from all compounds in the solution not just sugar, ex a wet growing year may have lower dry solids and higher water content.

In the scheme of things to watch a fermentation you are looking for a rate of change as sugar is consumed. You can use the refractometer even if the scale has not been calibrated for the specific mixture you are fermenting. It is done when the rate of change is zero.

 

[sjjan]

The refractometer will measure the change from all compounds in the solution not just sugar, ex a wet growing year may have lower dry solids and higher water content.

In the scheme of things to watch a fermentation you are looking for a rate of change as sugar is consumed. You can use the refractometer even if the scale has not been calibrated for the specific mixture you are fermenting. It is done when the rate of change is zero.

Thanks. I figured it would be something like this as it basically doesn’t matter what correction factor is applied, the change itself is sufficient. The only “thing” is that I am adding nutrients at 60 and 45 Oechsle (up to half way the fermentation), so I would have to figure something out where I could expect half.










§

 

[Rice_Guy]

Wine is very forgiving, if you have a grape must your nutrient content is probably enough to finish the fermentation. The issues develop when we start raising the temperature and yeast metabolize too fast for nutrient recycling OR we have a country wine which only has 2 kg of fruit per 4 liter jug OR we have a low nutrient fermentation as honey.

It won’t really matter

 

[salcoco]

regards difference in measured versus adjusted sg is your hydrometer reading correctly? is your refractometer automatic temperature correcting? it has been a while since I verified the spreadsheet against direct reading but I did not have such a variance , I did multiple trials before I went to refractometer measurements only.

 

[sjjan]

regards difference in measured versus adjusted sg is your hydrometer reading correctly? is your refractometer automatic temperature correcting? it has been a while since I verified the spreadsheet against direct reading but I did not have such a variance , I did multiple trials before I went to refractometer measurements only.

The refractormeter as ATC (automatic temperature correction). I will post a picture here. For the hydrometer, not sure what could do wrong there. There is such a thing as temperature correction with hydrometers, but the juice fluid temperature is close to calibrated hydrometer temperature and it doesn’t seem to make any difference.

As for temperature of the juice, I am keeping them cooled to around 16.5 degrees Celsius but one RVS tank has just 61 liter of wine, so I am letting it ferment at the temperature of the cellar (which is a bit higher) as the cooling hoses do not fit in such a small amount of juice. Welcome to RVS tanks with variable-height lids

As for temperature, SG and cooling temp monitoring, I created a dashboard, so I can follow it from my iPad or iPhone while on the go. Have a look at this dashboard here: Grafana