Measuring Gravity

[bostonbrewins]

I wanted to do things right from the start, so I ordered the gravity testing kit as well.

Now I know in kits it says to measure OG before fermentation begins, and you can clearly see these numbers stated in the kit instructions.

I know measuring the gravity again is the best way to see if fermentation is done - and it will always be lower. But how do you know when the final gravity has been reached? Is this a variable number based on each brew? Or is final gravity reached when its the same after a 1-2 readings???

I think I kinda talked myself through the answer the more that I typed, but I was just wondering about this.

Thanks

BostonBrewins

[dobe12]

The same readings over a few days will tell you it’s done fermenting. There are a LOT of factors that go into determining final gravity and it’s not an exact science, but all yeast strains have a general attenuation range. Most are around 75% give or take 5%. Some are lower (Irish or English strains) and some are higher (some Belgian and French). But again, there is no definitive answer as to what the final gravity will be exactly. Once you start brewing for a while, use different yeast strains, different brewing practices (mash temps, grain bill, fermentation temps, etc) you’ll get to know about where your beer’s gravity will finish… or at least within a few points.

[denny]

And just becasue a yeast has a certain attenuation rating is no guarantee that’s what you’ll get. It’s simply a way of comparing one yeast to another using the same wort. Wort fermentability is the big determining factor in attenuation.