The only way to know that fermentation is complete is to take a gravity reading from your fermentor.
Here are points to keep in mind 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 fermentor 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. It is extremely important that you are confident that your tube is cleaned and sanitized (TWSS).
- Open your fermentor in a non-drafty place. You want to minimize the chance that wild yeast get into your fermentor.
- Put the tube into your fermentor to a level that fills the tube with a good sized sample.
- Put your thumb on the end of the tube that is in your hand and slowly pull the tube out of your fermentor.
- Use the sample for whatever tool you use to get gravity reading like a hydrometer or a refractometer. If you are using a hydrometer, you may need to repeat the process to get a sample big enough for a reading.
- Some brewers return the unused part of the sample back to the fermentor. 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 or drink it. For instance, if you didn’t clean your hydrometer cylinder, don’t put sample back in the fermentor.
If you have hit your target final gravity, then go to your next stage of the beer’s life. I use samples from the primary fermentor for a few purposes. One is to check the gravity. The other, if I am brewing a lager, is to taste it for diacetyl and see if I need a diacetyl rest to have the yeast clean it up.
Hey, while you’re here… read some other blog posts that are related and you might find helpful: