Hydrometer VS. Refractometer

[fluffhead]

Santa gave me an ATC refractometer reading in brix. I calibrated it with tap water at room temp to 0. My latest batch brewed 2 weeks ago measured in at 16 brix bost boil. 1.065 sg according to on line calculaters. I started checking it a week later and its been at 7 brix(1.028) and hasent moved. Fearing an under attenuated beer, I roused the yeast warmed it to 70f for a few days and it still at 7 brix. I pulled a sample and took a hydrometer reading tonight and its at 1.008. What the fuck!? I tend to believe the hydrometer, but why the difference in readings? Refractometer not dialed in correctly? It's an ebay piece of shit? I'm retarded?

[BeaverBarber]

Santa gave me an ATC refractometer reading in brix. I calibrated it with tap water at room temp to 0. My latest batch brewed 2 weeks ago measured in at 16 brix bost boil. 1.065 sg according to on line calculaters. I started checking it a week later and its been at 7 brix(1.028) and hasent moved. Fearing an under attenuated beer, I roused the yeast warmed it to 70f for a few days and it still at 7 brix. I pulled a sample and took a hydrometer reading tonight and its at 1.008. What the fuck!? I tend to believe the hydrometer, but why the difference in readings? Refractometer not dialed in correctly? It's an ebay piece of shit? I'm retarded?

yep...believe the hydrometer. I have a brix refractometer that is reliable for OG but not FG. I also know of a brewery that uses a refractometer for OG but will switch to a hydrometer for FG. I'm not at all sure why this is the case, but I'm sure someone here will know. I've never bothered to research it since I have such a simple work-around.

[fluffhead]

Thats good to hear! Thanks

[anday6]

Refactometers only read a sugar water solution. Alcohol throws off the measurement. Only use the refrac for the OG and stick with a good old hydrometer for FG.

[Elbone]

If you know the OG, you can use a refractometer to take a FG reading, but you have to run the numbers through a calculator that takes the alcohol into account. Here's the one I use

SO much less hassle than a hydrometer. And harder to break. I must've broken 5 or more hydrometers over the years. I refuse to buy another one.

BTW, You should calibrate your refractometer with distilled water, not tap water.

[BeaverBarber]

If you know the OG, you can use a refractometer to take a FG reading, but you have to run the numbers through a calculator that takes the alcohol into account. Here's the one I use

SO much less hassle than a hydrometer. And harder to break. I must've broken 5 or more hydrometers over the years. I refuse to buy another one.

BTW, You should calibrate your refractometer with distilled water, not tap water.

Thanks! Maybe I should've researched this so that my life would be easier. Once again my laziness is getting in the way of my laziness.

[Stinkfist]

it is always good to double check a refract with a hydrometer....I bought a refract off ebay and that thing is off even for OG readings...yes I calibrated with distilled and it still reads way off. so just as a warning always double check them with a hydrometer at least at first...

[Ozwald]

You'll have to do some calculations to get an FG with a refractometer - the alcohol in solution will always throw it off. ProMash has an automatic calculator, so I'm assuming BeerSmith does as well. There's several other ones over the web, such as the one on MoreBeer's website. Another thing to note, even though it says ATC, it's bullshit. You've got to be fairly close to calibration temp. When I first got mine I took a sample at 80 & noticed that the reading changed significantly when it dropped to 65. I've heard others experience the same thing. Now I just aim for that 60-70 window unless I'm brewing something very specific, such as for a wedding or gathering. If it's just a regular brew to keep my taps pouring, I don't really care all that much.

They were designed for use in the wine industry, measuring simple sugars. The more complex sugars from malt will also throw off the reading, but that difference is very small - maybe a half to a full point, in most cases, depending on the wort.