Gravity Readings During Fermentation
We had a reader write in to ask us about how to take a gravity reading during fermentation because he had never done it before.
To tell you the truth, I haven’t done one either. With ales, I would let them sit in the primary fermenter for 2 weeks and then bottle them up. I would take a reading at bottling and whatever my hydrometer said, I would take.
With this lager, two weeks may not be enough time. It may have to stay in primary fermentation for a month. I won’t know until I check the gravity on Sunday.
Here’s a few thoughts about gravity readings during fermentation from my perspective:
- You want to get a long, thin cylinder/tube of some sort that is easy to clean and sanitize. I have seen homebrewers use (new) turkey basters. I have seen homebrewers use glass wine thieves. I have a nice plastic one that can be broken apart into 3 pieces for easy cleaning. Whatever you use, you want to make sure it fits the opening of your fermenter and it has openings on both ends.
- Like I alluded to earlier, clean your tube well and sanitize it before you use it to take your gravity reading
- Open your fermenter in a non-drafty place. You want to minimize wild yeast getting into your fermenter.
- Put the tube into your fermenter to a level that fills the tube with a good sized sample…a half filled tube should be good.
- Put your thumb on the end of the tube that is in your hand and slowly pull the tube out of your fermenter.
- Use the sample for whatever tool you use to get gravity reading like a hydrometer or a refractometer.
- Some brewers return the unused part of the sample back to the fermenter. If you think it is clean, then go ahead. If you feel like you have compromised it in a way that may bring infection or other bad things to your beer, just chuck it.
If you have hit your target final gravity, then go to your next stage of the beer’s life. I plan to use the sample I take on Sunday for two purposes. One is to check the gravity. The other is to taste it for diacetyl and see if I need a diacetyl rest to have the yeast clean it up.
on January 28th, 2010 at 4:39 pm
I like to setup a “mini fermeter” to check my gravity. That way I have no risk of infection and I also know exactly what is going on in the full scale version. Check out my post on it here: http://breweryreviewery.com/?p=316
on January 29th, 2010 at 1:11 am
Honestly, I also don’t do mid-fermentation gravity checks - its just too much of a pain and you’ll lose about 1/3 to 1/4 a bottle beer each time you do it with a hydrometer. Using a refractometer is the way to go, although it is not straight forward once fermentation starts (i.e. the alcohol in solution will throw off the refractometer reading - the more alcohol, the more trouble it gives the measurement).
One resource I remember hearing about is the MoreBeer.com site. They hace posted at least one video on using a refract during fermentation, as well as developing a spreadsheet that will allow you to take SG measurements during the ferment (it mathmatically removes alcohol’s effect on the EG meadure). A link to this resource can be found below.
http://morebeer.com/learn_vids/vids_refract
Good luck!
-JW
on January 29th, 2010 at 5:18 pm
For a nice (javascript-driven) page to calculate alcohol from OG and Brix, try http://brew.stderr.net/refractometer.html . If you’re brave, look at the page source for their calculations.
I use a refractometer that strongly resembles the one Morebeer sells, and is ubiquitous at Ebay shops. Using it is a breeze, but the contrast of the reading scale is highly dependent on the clearness of the fluid you’re testing- and Bacchus knows beer isn’t necessarily clear.
on February 1st, 2010 at 10:36 pm
[…] took a gravity reading yesterday following my own advice about how to do it. My hydrometer read 1.015 which is a little lower than my target, but in the […]