View Full Version : refractometer/hydrometer probems for a noob

04-30-2017, 12:52 PM
Starting out I bought a hydrometer and a cheap Chinese refractometer. It was cheap and I tested it with distilled water and a sugar solution against the hydrometer and the readings were consistent. Since I was familiar with the refractometer use and convience, I have used it exclusively. I started a 5 gallon batch of plain mead (OG 1.110) and a 1 gallon batch of bochet (OG 1.130). Both stalled, both at 1.060, I attempted to restart both with Permier Cuvee (what I had), the mead restarted and fermented for a few days the stopped at 1.030, the bochet would not go. On the advise of a local brew store I pitched VK1-V116 into both. Both refused to move.
The mead does not taste sweet and is more potent than I was aiming for, the bochet taste like sweet non-salty soy sauce, not very strong or pleasant.
Last night I was having a glass of red wine (dry) and decided to check the SG with my refractometer, it read 1.030. ???, I poured some into the test flask and took a hydrometer reading, 1.000. I did the same with the mead, 1.002, the bochet, 1.028. I repeated my initial test with a sugar solution in distilled water and the refractometer/hydrometer gave the same readings.
What gives? Why different readings ? From taste alone, as well as scenario, I believe the hydrometer readings. Is it just a cheap refractometer, does the color or particulate matter in the must change the reading? It gives consistent readings (albeit incorrect).

Do you pour your sample from the test flask back into the carboy after testing? Couple of drops on the refractometer is more convenient and doesn't risk contamination BUT in my case is not very accurate.

04-30-2017, 01:16 PM
I seem to remember reading somewhere that a refractometer was not the best tool for mead and that only with a hydrometer could you get accurate readings. I don't remember why that was said or even if it's true, but I have heard several anecdotes like yours. Frankly, the hydrometer is a pain in the ass, but only for the first week when you're trying to determine the 1/3 and 2/3 breaks. After that, once a week is enough. If you want to return the sample, that is. If you don't return the sample, it's not a pain at all. I don't return the sample. I taste it and throw out the rest.

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05-08-2017, 03:48 PM
refractormeter does not work once fermentation has begun.
After fermetntion has begun you need to use a hydrometer

05-08-2017, 04:09 PM
Refractometers don't work in alcohol, but there are formulas and calculators out there that can correct for it. I have no clue how to use one, but here's an example:

05-08-2017, 09:04 PM
I agree with the posts about the problem with using a refractometer in the presence of alcohol. Refractometers are calibrated to measure how much light bends as it passes through water. Where there are, say, sugars dissolved in the water the light bends at known and calibrated angles that are presented as either brix or specific gravity readings on the refractometer. Where there is alcohol mixed with the water the light bends at a different angle - and the more alcohol there is the less the light behaves as if it is passing through water. But there are formulae for translating the reading.

But to your other point - restarting a stalled fermentation. What I would do is create a starter of say 1 cup and then add to this starter 1 cup of the stalled fermentation. When you know the 2 cups are actively fermenting you then add 2 cups from the stalled batch. And when those 4 cups are actively fermenting you add 4 cups from the batch ... and you repeat this until all the stalled batch has been transferred to the starter. Rationale: if there is some significant problem causing the fermentation to stall then simply adding more yeast may not restart the fermentation. The new yeast may be overwhelmed by the problem. The idea is to "dilute" the problem by patiently adding from the problem batch to the batch that is actively fermenting...

05-09-2017, 06:14 AM
Calculators will make the calculations for you. That is why they exist. If you have the OG, many of them can calculate the error from the alcohol in a refractometer since its a pretty simple operation. The one from northernbrewer works fine

You can return the sample to the batch as long as you used a clean container. A 100 ml probete is a good investment (they are cheap, tall, useful for other things and dont need much must) but you can use jars or glasses.

05-09-2017, 10:40 AM

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05-10-2017, 11:42 AM
I taste it and throw out the rest.

What a shame ;)) . I drink it all.

05-10-2017, 01:36 PM
Haha! Too sweet for me on day three!!! And 4 !

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05-10-2017, 06:44 PM

10-09-2017, 05:00 PM
I recently got a refractometer and have been very pleased with it. It saves me the time, mead and cleanup involved in using a wine thief with a hydrometer.

As others have noted, however, as the alcohol in the must increases, the refractometer readings become progressively more inaccurate. As Dadux pointed out, there are websites like northernbrewer that have calculators which will calculate the current gravity, given the original Brix and the current Brix.

I found it more expedient to build that calculation into my own mead log form. It took a bit of searching to find the formula, so I thought I'd share it with others who may want to use it in their own mead logs or programs.

The formula calculates the Current Specific Gravity as:

=1.001843 - (0.002318474*OB) - (0.000007775*OB*OB) - (0.000000034*OB*OB*OB) + (0.00574*CB) + (0.00003344*CB*CB) + (0.000000086*CB*CB*CB)

Where OB = Original Brix and CB = Current Brix

You can paste this formula into a spreadsheet or use any programming language to incorporate this conversion formula into your applications. A spreadsheet example would work like this:

Name cells A1, B1 and C1 with labels "Original Brix", "Current Brix" and "Current Gravity" respectively
Format cells A2 and B2 as numbers with 1 or 2 decimal places. Format cell C2 as a number with 3 decimal places.
Paste the above formula into cell C2, substituting 'A2' for 'OB' everywhere it occurs and 'B2' for 'CB' everywhere it occurs.

Now, entering the original gravity (in Brix) in cell B1 and the current gravity (in Brix) in B2 will result in the current gravity (in S.G.) being displayed in cell C2.
If your mead logging form is a spreadsheet, you can use this formula to automatically convert your refractometer readings to S.G. everywhere they are useful to you.

Miruvor maker and Eternal NewBee
Mithlond Meadery, Grey Havens, Eriador