driving the FG down?

[NewBrewerTFM]

Perhaps this is a stupid question but, if the objective of fermenting beer is to produce, in addition to the wonderful flavors, some alcohol, then don’t I want to drive the FG as low as possible? Like I said, perhaps it’s a stupid question, but I’m relatively new to brew science and trying to learn so please share some technical insight. What are the pros and cons to lower FG? How does one drive the final gravity down?

 

[Hammy71]

Sometimes you want to have a low FG. Beers like IPAs usually thrive on that. But, if your making a stout.....mouth feel is essential. So, a higher FG is required. Remember, not everything about beer is alcohol. Paradoxically, you can make a Russian Imperial Stout that is 10% ABV and still have a FG that is 1.020+. Different beers require different techniques.

 

[NewBrewerTFM]

So it’s relatively easy to understand how to control OG but how does one control FG?

So moth feel, lower FG = Dry? Higher FG = sweeter?

 

[sherma]

So it’s relatively easy to understand how to control OG but how does one control FG?

So moth feel, lower FG = Dry? Higher FG = sweeter?

Yes, you are correct. Generally, lower FG = dry and Higher = sweeter.

You control it by choosing the appropriate OG and using a yeast that attenuates to the level you desire. Each strain of yeast has an attenuation range, meaning they will convert a certain percentage of the sugar to alcohol.

 

[Yooper]

FG is a function of several things- the yeast strain attenuation, the ingredients (some ingredients are more fermentable than others), mash temps, and so on.

Some beers should finish crisp and dry (think American light lager) and some should finish almost "chewy" and sweet (think sweet stout).

To make a light American lager, it's important to use flaked corn or rice to lighten the body, and create simple sugars which will ferment fully, and to mash at a low temperature. I've had light lagers finish at 1.005, which is desired.

To make a thick sweet stout, I'd use crystal malt (less fermentable), lactose (non fermentable), and mash at a higher temperature with a less attenuative yeast strain so it would finish at 1.022-1.026.

Both beers may have a very similar ABV, but they are totally different in the sweetness level, the quaffable beer will be lighter and crisp and dry, while a sweet stout is almost a dessert beer and quite filling and sweet.