I pulled a sample last night to check gravity since I was planning on bottling Saturday anyhow, and my reading is closer to 1.018. This isn't WAY off, but I am wondering what could have made this difference...even if it is slight.
I am learning and I want to try to do everything right...it's an obsession.
Any ideas?
What was the temperature of the wort at which you took the original gravity reading, and the final gravity reading? Most hydrometers (every one I ever used) are "accurate" at 60°F, so if not taken at this temp will be slightly off. So even if your OG appeared to be what the kit claimed it should be, it may have actually not been what your hydrometer said. Same is true for your final gravity. This doesn't mean if you check it at 61 degrees that you're going to be wayyyy off... this is not the case. But checking it at 85 degrees might throw you some. I don't know the math off the top of my head to know how far off it is. But I usually try to take readings as close to 60 as possible.
What I normally do when transferring chilled wort into the fermeter is take a small sample (enough to fill the hydrometer tube minus the volume of the hydrometer... either fill it with the hydrometer in it and wait for it to float, or before hand have an approx mark that would allow it to float and not overflow when you drop it in the tube) and pop it in the fridge for a bit, and then finish up my work. Once everything is sealed up and cleaned up, I take the sample out of the fridge and check with thermometer. If it's below 60, I'll grip with both hands and swirrel around a little so my hands warm it up, and then take gravity reading once the thermometer says 60.
Same way when checking prior to bottling; My fermentations are usually taking place in the house, which is usually above 60°F, so I pull a sample and chill it down to 60, then take the reading.
All that said, you are still close and I doubt you did anythign seriously wrong. I wouldn't worry about it, and hopefully my long-winded methods will give you some tips on future readings.
Thanks, cheers, and enjoy your beers!
Nic
Edit: Oops, didn't notice BadNewsBrewery already said kinda the same thing about temps.
But another thing to note is to be "sure" your fermentation is done prior to bottling, take a gravity sample 2 or 3 days in a row, or at least several hours apart, and compare them. If three in a row are trending downwards, it's still fermenting. If three in a row are dead even, consider it done. And make sure you don't dump your samples back in the fermenter or bottles. I usually drink mine.
