Reading a Hydrometer

[rottenapple]

Can/Will someone explain to me how using a hydrometer tells you that your wort is done fermenting?

 

[Yooper]

well, you take the sg three days in a row and if it doesn't change (and if it's in your suggested/expected area of sg) then it's done.

 

[rottenapple]

Thanks for the rapid response Yoop. I understand the mechanics of the unit its the chemistry part that is confusing.

I'm talking with no experience so bear with me,
Say you take your initial reading and it reads 1.042 and you wait your 7-10 days to ferment, you take your readings for three days and notice no change. Its done right?
Is it the final number that you get on the hydrometer or is it just the fact that the reading itself hasnt changed in three days?

 

[Beerrific]

Is it the final number that you get on the hydrometer or is it just the fact that the reading itself hasnt changed in three days?

That is a good point. Really you should consider both. If you get the same number for 3 days in a row fermentation has stopped or is moving very slowly. If you are at or near your expected FG then it is time to move on (bottle, keg, secondary, whatever). If you aren't near your expected FG then measures need to be taken to 'wake' the yeast and have them finish fermentation. You would hate to bottle just because your gravity hasn't changes in 3 days, wake the yeast, have them finish fermenting in the bottles, and have bombs on your hands.

 

[rottenapple]

You guys are extremely helpful just one more ?? and I think I'll get it.

How does one determine their expected FG.

 

[Philip1993]

It varies widely by style, but as a rough rule fermentation is complete when your FG is about 80% of your OG and stable for 2-3 days.

 

[homebrewer_99]

You guys are extremely helpful just one more ?? and I think I'll get it.

How does one determine their expected FG.

Some yeast pack info tells you the (expected/anticipated/guesstimated) attenuation %. Most are about 75%.

Divide the OG by 4 using the last 2 numbers only, example...OG 1.050 (50/4=12.5) the FG should be about 1.012.

When the FG hits those numbers or really close to it then the beer is done fermenting and ready to rack to a secondary for clearing.

 

[rottenapple]

Thats what I needed to know! Thanks alot 4 being patient and working this one out!

 

[e lo]

Hey, at least you're using your hydrometer. I've not been brewing very long, but I'm shocked by how many people don't use one!