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Probably a dumb rookie question about temp corrections for hydrometers
I'm very new to brewing and I've only done a couple of 1 gal. batches from this kit I bought on E-bay to gain some experience while I waited to get back to work from a lay-off. Well, now I have a job and bought a ton of equiptment from midwest supplies that I'm still waiting for yet. I have an IPA that I want to brew this weekend, assuming I have all the stuff I need by then. I did get a hydrometer though, and I'm a bit thrown off my the temperature correction chart that came with it. The one I bought says that it is calibrated for 60 F. I read Palmer's book and he says that most are calibrated to 59 F. He gives a chart for temp corrections based on that. I was wondering if I could use that chart for my hydrometer? If not, then the chart that came with mine confuses me much. It says "This hydrometer is calibrated to give correct readings at 60 F. If the temperature of the liquid is higher or lower than 60 F, the final gravity should be adjusted as follows: 50F -0.002, 59F -0.001, 68F None, 77 +0.001, 86F +0.003, 95F +0.004" So do they mean final gravity as in fermentation done F.G. or no? And if so, what about the O.G.? And if it's calibrated to 60F why is there no correction for 68F? How do these temperature corrections work?
Maybe there is a misprint when it says it's calibrated at 60. Just add or subtract the appropriate numbers they gave you. A degree or two off isn't going to make that much of a difference. O.G. will be the specific gravity reading before fermentation. Your F.G. or final gravity I've also seen T.G. (terminal gravity) will be the specific gravity reading after fermentation is complete.
All hydrometers that I have seen are calibrated to 60 F. Honestly, the corrections for temp difference are so minimal that I have never bothered with them. Most of my beers ferment around 75-80 F and I just use a straight reading.
Looks like I forgot to answer part of that..... there are corrections because liquid is more dense when it's cool and less dense when warm. Because of this the hydrometer will float differently depending on temperature.
I totally get the idea of how a hydrometer works and why they tell you to do the corrections. I was kinda confused by them saying that it's calibrated to 60, but 68 doesn't need a correction and 59 does. And that they said "Final gravity", when I'd assume that both the final and original gravities would be affected by temperature. If it's not a big deal and I can just read it as is despite the temperature, then great. Thanks much for the advice.
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