what can cause improper gravity readings?

Besides temperature, are there certain things/tips to consider when taking a gravity reading.
I ask because I was racking to secondary and when tilting my carboy a lot of the yeast cake stirred up. I was wondering if that could contribute to an improper gravity reading.
Also, how do you guys actually grab your sample from the carboy? Do you do it while siphoning? If so, I would imagine, since alcohol rises and sediment...well...settles that you'd want to pull the sample from somewhere in the middle of the batch.

temprature too high
everything not mixed when using top off water
hydrometer/refractometer not calibrated
co2 bubbles sticking to the hydrometer in the sample tube

I use a refractometer now, and just pull about 5 drops from the top, it is pretty well homogonized.

Arkador said:

I use a refractometer now, and just pull about 5 drops from the top, it is pretty well homogonized.

Click to expand...

meaning the mix at the top is similar to the middle of the batch?
what about stirred up yeast/trub? can that effect the reading?

chirs said:

meaning the mix at the top is similar to the middle of the batch?
what about stirred up yeast/trub? can that effect the reading?

Click to expand...

No clue. My sample always comes form the top.

I would expect trub and some yeast wouldn't throw off the reading, all that stuff is in suspension when we take our OG reading.

Not to insult you, but are you reading it properly? I have seen a few people ask the same question only to realize they read the hydrometer incorrectly...myself included on my first beer lol.

no insult taken. i think i'm reading it properly...but I do have to refer to the hydrometer booklet every time i use it...

I've actually been wondering about this myself, since i've had a few beers that seemed to finish way too high. Like 1.020 when I was expecting more like 1.015, where I pulled my FG samples from the bottom and had a ton of sediment. But I dont think that the sediment would affect the reading, since all the stuff is in suspension and not dissolved.

I actually let one sample settle in the fridge for a while and the reading after it was cooled was close to the temp corrected reading beforehand. But, I didn't write any of the readings down, so that's not exactly empirical evidence.

someday i'm going to brew something called an "empirical ale"...

Always de-gas the sample, because CO2 on the hydrometer can throw the reading off.

Alcohol and water do not separate once mixed, so where you draw the sample will not matter.