Specific Gravity whats the story

[nickjam]

I have been reading the forums and a common problem for new people is to know when to remove the beer from primary fermintation and place into secondary fermintation. I know that when the airlock stops bubbling that is a good indication, but the best way seems to be specific gravity. I know to take a reading of my wort then take one before I transfer into secondary fermintation.

Do I take the first reading before pitching my yeast or after?

What is the rule of thumb for specific gravity before moving to secondary for different beers?

I read somewhere you divide by four so if it starts at 1.042 then you take 42/4=10.5 and so your final should be about 1.010 to 1.011?

Is this information printed on the kits for the different beers?

Thank you in advance for the help.

 

[Professor Frink]

Measuring specific gravity is the best way to determine if fermentation is finished - if you check over the course of 2 or 3 days and it doesn't change, it's pretty much done fermenting. However, I have been to lazy to check the gravity at times.

As far as how much the gravity will change, that depends on your SG as well as your yeast. A higher attenuating yeast will results in a lower final gravity than one with a a lower attenuation. Also, a big beer such as a barley wine with a very high SG typically won't drop to as low as a final gravity. Your /4 rule is a pretty good guidline for your average ale.

And you want to take your gravity reading right before you pitch the yeast.

 

[fritz_monroe]

I don't think it really matters if you take your reading before or after pitching the yeast. The yeast won't make a big difference in the reading. I guess if you use a starter, the extra addition could make a slight difference, but you would only add about a quart to the 5 gallons, so...

As for the SG to move it over, I don't take a reading. I move to secondary after 1 week in the primary.

 

[Evan!]

Do I take the first reading before pitching my yeast or after?

If you're pitching a big starter, I'd take it after you pitch, because the starter wort will affect the gravity readings. Otherwise, it doesn't matter.

What is the rule of thumb for specific gravity before moving to secondary for different beers?

There isn't a rule of thumb. If you take two readings, several days apart, and you witness little to no change, then fermentation is done. Your attenuation (percentage of sugar that is converted to alcohol) depends on the yeast strain. Usually the yeast manufacturers will list the attenuation on the package.

I read somewhere you divide by four so if it starts at 1.042 then you take 42/4=10.5 and so your final should be about 1.010 to 1.011?

I dunno. I use ProMash. Your final "should be" whatever the attenuation measures it out to be. Your desired final gravity depends on the beer style. Pilsners should be dryer than sweet stouts, typically. According to promash...

For example, let's say you're using Wyeast 101 (American Wheat). Its listed attenuation is 74-78%.

OG=1.042
at 76% attenuation, your FG should be 1.010.

The listed attenuation for each strain is an estimate, and is also dependent on other factors, like how many unfermentable sugars are in the wort, the ferment temps, and how much you aerate the wort prior to pitching. If you add, for example, maltodextrine (an unfermentable carbohydrate from corn) or lactose (also unfermentable sugar) to the wort, then the yeast won't be able to ferment as high of a proportion of the sugars, so your attenuation will be lower.

Is this information printed on the kits for the different beers?

Never used a kit, but I doubt it.

 

[KopyKat]

As for the SG to move it over, I don't take a reading. I move to secondary after 1 week in the primary.

This may work for most simple ales but do not use this as an absolute. I recently did a pale ale with Wyeast 1272 at 60° and it was 10 days before I got my finished gravity and the krausen had fallen. Even then, I racked to secondary, a small head of krausen came up and it dropped another point.

High gravity beers may take longer and lagers are usually 2-3 weeks before primary is finished.

A hydrometer is the the sure way. You can get to know what beers will finish when under specific conditions.

Some of the conditions that affect when a beer is finished are:

1. Temperature control and fermentation temperature.
2. The particular yeast you are using.
3. The viability of the yeast.
4. Yeast count of starter if used.
5. Gravity of wort.
6. Amount of nutrient availible - trub, break, added nutrient, etc.
7. Amount of aeration or oxygen added, if any.
8. The God of Fermentation (whether they are on duty or on a break)

It never hurts to leave an ale in the primary longer than needed. In fact, there are many brewers that do not rack to secondary at all but leave ales in the primary several weeks and claim that they make better beer by leaving the beer in the primary for a couple of weeks or so after fermentation is complete. I have done this with success myself though I can't say it was better but certainly was just as good.

Since I have only one primary and room for only one in my temp controlled freezer, I usually rack to primary. I wouldn't if I had more room though.

 

[Bobby_M]

Honestly, it doesn't really matter exactly when you rack as long as most of the fermentation is done. Whether you gauge that by watching airlock bubbles, taking a gravity reading, or eyeball the level of clarity (clear carboys only). If your krausen has fallen completely and the airlock is barely moving, it's probably time. I take a reading after I rack, just to make sure I'm close. It's not like you have to worry about bottle bombs when you're moving to secondary. When in doubt, wait three days.