Beer Forum

Hey everyone.

I recently received a refractometer, which is a truly awesome tool, but I'm having an issue with it. I've had it for about 5 batches now, and I use it primarily to measure gravity during and before the boil so that necessary adjustments can be made. However, I would also like to be able to use it as a complete replacement for my hydrometer, just because it's so much easier. The only problem is this. When I make "higher gravity" measurements, e.g., pre or even post-boil, the measured value matches up nicely with hydrometer values, which I have been taking as a check. In other words, the refractometer measures starting gravities just fine. But, when I attempt to measure final gravity, the refractometer always reads way too high. For example, last week I brewed an American IPA. O.G. was about 1.057, and this was the value read by both the hydrometer and the refractometer. Great. But this morning when I measured the F.G. and got ready to transfer to a secondary for dry hopping, the refractometer said that is was 6 Plato (about 1.024)! When I took a hydrometer reading, it told me that the beer was at a much more reasonable gravity of 1.010.

I calibrated the refractometer using distilled water as recommended by the manufacturer, and like I said at higher gravities it works fine. For some reason it is just having trouble measuring lower gravities accurately,

Any thoughts or similar experiences?

Thanks!

if you go on to morebeer.com under their education or tutorial section, they have an excel spreadsheet with the calculations already factored in. just plug in your numbers and it does the rest. the reason for it being "off" is during your OG reading you are dealing with sugar in water and in your FG you are dealing with sugar in alcohol. Cheers, Drew

The unfortunate (because they are so easy to use) truth about refractometers is that they are pretty useless once fermnetation starts. This is because dissolved sugar and ethanol both increase the refractive index of an aqueous solution.

There are various correction tables and formulas but unfortunately it really depends on the particular beer. Breweries do use refractometers to monitor fermentation and estimate alcohol but the refractometers have been calibrated against densitometers or accurate hydrometers for the particular beer being brewed. This is quite practical if you have a lab and brew Kölsch 2 days a week. It isn't very practical for home brewers.

Ahhh! Of course! I didn't take into account the presence of alcohol. How silly of me.

Thanks guys.

If you use any brewing software, it should have a place to correct the reading for alcohol. I use beersmith and brew pal and they both have a spot to correct fit it. I've also use the morebeer spreadsheet without problems.

It's a little bit of a pain, but with how much less beer and equipment needs to be sanitized it makes up for it.

PSUHomebrewer wrote:If you use any brewing software, it should have a place to correct the reading for alcohol. I use beersmith and brew pal and they both have a spot to correct fit it. I've also use the morebeer spreadsheet without problems.

It's a little bit of a pain, but with how much less beer and equipment needs to be sanitized it makes up for it.

+1

Using a refractometer/correction formulae for gravity measurements after fermentation has begun is sooo fast and easy and requires such a small sample that it more than makes up for any very small inaccuracies in measurements. You don't need accuracy beyond what the refractometer provides, IMHO.

How can the refractometers reading be adjusted after fermentation if the final gravity is unknown, and may be off of what is expected?

Can you describe how the post fermentation adjustments work?

Because I'd love to use a Refractometer instead of a Hydrometer

I don't know what the formula is, but in brewpal you place the reading in, and select for presence of alcohol and it gives you the corrected reading. In beersmith there is the same feature, but there is also a section where you can calibrate the software to precisely correct for the presence.

Though in all actuality does it matter if the corrected value is off slighty? A few tenths abv isn't going to change anything much/if at all.