hydro readings

[alex510]

old -very old time (circa 1987)brewer getting back into the grove of brewing. I never had a hydrometer before-So I brought all my equipment used off of craigslist pennies on the dollar. so I could not buy one back in the day and now I have 3 lol. So is there a link on what it is for?

 

[VikeMan]

It's for measuring the gravity of your wort before fermentation and your beer after fermentation, so that you know attenuation has finished and can compute your ABV. Here's one of many videos:

Ignore the "potential alcohol" stuff, but pay attention to how to read the specific gravity scale.