Sg

[Sam516]

I have a question about what exactly changes the OG of a beer. Is it the kind of malt? The amount? The volume of the water it is boiling in? I am a little confused about what controls the gravity of the beer. Someone please let me know - I need to learn!

 

[the_trout]

Its all those things and more. Pretty much anything you add to your boil will affect your OG. Think of the OG as the density of the beer, the more stuff disolved into it the denser or higher the OG will be.

 

[1Mainebrew]

Ok, so the gravity starts out high because of the amount of sugars in solution make the wort heavier than water (which has a sg of 1.000). As the yeast eats the sugar it produces alcohol. Alcohol is lighter (has a lower sg) than water. As more alcohol is produced, the sg of the beer goes down.

The mash has a lot to do with how fermentable a wort is, or how much sugar the yeast will have available to turn into alcohol. In an extract recipe it has more to do with how you treat your yeast, like are you pitching sufficient yeast, and what temp do you pitch at, and what temp do you ferment at.

 

[rycov]

As the yeast eats the sugar it produces alcohol. Alcohol is lighter (has a lower sg) than water. As more alcohol is produced, the sg of the beer goes down.

not to mention that its also less dense because there are less sugars in it.

 

[Sam516]

If i take the sg of my wort before I pitch the yeast but after I cool it will it be different than when I take it after I pitch?

 

[rycov]

immediately after you pitch? probably not. after several hours? possibly

 

[bgrayson726]

It will be significantly lower after fermentation is complete.

 

[Sam516]

Do steeping grains effect the sg at all? Or how about the difference between light and amber dried malt extract? Any differences in the expected OG of the wort?

 

[1Mainebrew]

Do steeping grains effect the sg at all?

Yup, they certainly do. They add body and complexity to a beer by adding unfermentable sugars. That is why a beer with too much crystal malt or cara-- will finish high from a sg standpoint. Because those sugars are not available to yeast to chew on and turn into alcohol.

 

[boo boo]

I have a question about what exactly changes the OG of a beer. Is it the kind of malt? The amount? The volume of the water it is boiling in? I am a little confused about what controls the gravity of the beer. Someone please let me know - I need to learn!

The amount of sugar in solution for a given amount of water. More sugar = higher gravity.