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ok dumb question..
taking a hydrometer reading, i fill the tube up , toss the hydrometer in , and give it a swirly.. there's enough foam / bubbles on the surface probably from the star san on the thief or what not... soooo, how to prevent that to get a good reading?

Use a refractometer

BigWally wrote:Use a refractometer

i thought they were inaccurate at the end of fermentation..

RobDrechsler wrote:

BigWally wrote:Use a refractometer

i thought they were inaccurate at the end of fermentation..

There is a formula to convert the FG reading on a refractometer to account for the alcohol present in your final beer. I just use this site - http://onebeer.net/refractometer.shtml

A related problem I have had with post-fermentation hydrometer readings is the formation of bubbles on the hydrometer itself. Even though the beer isn't carbonated it still has a lot of CO2 in solution from fermentation. I can actually watch the hydrometer slowly rise as the bubbles form. I have found that patience works here - just let it sit for awhile and periodically spin or tap it.

I agree with Walter, use a refractometer. As far as measuring gravity once the fermentation is done, I never bother. I go to the always reliable taste test, I figure that once the yeast is pitched, it's all pretty much in God's hands anyway. If the beer is under attenuated, I'll figure that out when I taste it but I rarely have that problem since I try very hard to pitch a ton of yeast (unless I'm making a heffe in which case I alway underpitch on purpose). Now some might say that I don't know the ABV of the beer but again I really don't care, all I am really interested in at the end of the day is the taste.

Since my taster is not that good I rely heavily on my measurements. When I read this post I thought "what a good idea". I normally take both a OG and Brix at the start of fermentation. Brix requires a much smaller sample. So I tried this with my most recent batch of beer on my forced fermentation sample. My OG was 1.049 and Brix 12.2 they agreed. Today my SG was 1.0175 measure with a calibrated final gravity hydrometer. My brix was 6.0. The calculator at onebeer.net resulted in a SG of 1.008. That is a full gravity point difference. Any idea why?

Probably nothing more than sampling error. If things are not coming out they way you expect them, take a couple other readings as they say, "stuff happens". What I do is take a gravity reading with my hydrometer once the wort starts to boil and after the hot break has calmed down. If I have missed my gravity for some reason, I just boil for a little longer until I get my estimated beginning gravity. I then just boil for 1 1/2 hours and I know from experience what I will end up with after I'm done. The whole trick with this stuff is to do things the same way every time you brew. Since malted barley (or wheat or whatever) is a natural product, there are always going to be slight variations in the amount of starches contained in the grain which can cause you to be just a little high or low. A point or so one way or the other is no big deal, if you can taste the difference you are certainly a better man than I.

I rechecked again today with re calibrated final hydrometer and Refract. OG = 1.049 and brix 12.2. Today 1.016 and Brix 6.5. So while they measurements agreed at the beginning of fermentation, they still do not give the same result.

Just put a little more than you need in the tube and let it overflow the bubbles. That's what I do.