Yeast Washing / Yeast Rinsing

Save Money and Start a Signature Strain
So you have just racked your beer out of primary fermentation. The yeast has been active for a number of weeks and has multiplied so much that you're left with a half gallon of yeast slurry. Well, that slurry can be used in at least four more batches of beer, and each of those beers will make four more yeast slurries which can each be used. The Sourdough strain that's been around San Francisco since 1850 is still being used today. You could make a beer today and if the yeast is properly harvested, and the harvest is continually used, you could carry the strain on with your unique signature until you're kid's kids are making beer with it.

I would like to explain, in detail, the process that works for me. Ideally, you can rinse your yeast the day that you rack off the primary, but there is no harm in waiting a few days (just put the airlock back on). This doesn't require any kind of acid wash, it's just adding water to the dregs of a batch to re-use the yeast on a later date. Here is my arsenal of useful equipment and required components:

Things I use:
1. Batch of beer just racked out of primary, the 'dregs' as they're sometimes called.
2. Two 1 gallon jugs (glass apple juice containers).
3. At least four mason jars with lids.
4. Racking cane with tubing and rubber hood.
5. A bucket with sanitizer solution.
6. Funnel.
7. A square of tinfoil.
8. Spray bottle with sanitizer handy for last minute sanitizing jobs.

The Process and the Nuances:
1. Sanitize the two 1 gallon jugs and then fill them with tap water. Highly hopped beers can take more water because there are usually more particles to filter out, so if the beer was an IPA I will prepare 2 gallons of water. Otherwise, 1.5 gallons is just fine. There are three levels of care that I have given my Yeast Rinsing Water in the past and I will explain the benefits of each:

• Boiling and Cooling Overnight: this is the longest of the processes and gives you the best 'clean slate' for your yeast. Boiling your 1.5 to 2 gallons of water for 10 minutes is said to diminish all additives (chlorine, fluoride, etc.) that your water company puts in your tap water. Boiling would also kill any bacteria that might be present. Place some sanitized tinfoil on the jugs and allow them to sit overnight in the fridge. This method, although long in process, is said to have the least risk of infection.
• Letting Sit at Room Temp: place some sanitized tinfoil over your jugs and let them sit in a room temperature location (or in a fridge) for a number of hours, between 4-8. Allowing tap water to rest has been said to help diminish harmful additives. This has a low risk of infection (unless fridged, then slightly lower) since it wasn't boiled, but might give you peace-of-mind when it comes to your rinsing water.
• Using Straight From the Tap: this is how I do it presently. The water in my town is known to be very good for drinking and beer making. I sanitize my 1 gallon jugs thoroughly, fill them with water, cap with sanitized tinfoil, and let them sit as I prepare the next step. I've made great beer using yeast rinsed with this minimal amount of care to your water.

2. Now that your 1.5 to 2 gallons of tap water are ready to rinse your yeast, you can take the next step. Sanitize your funnel thoroughly, then place it on your fermenter with the dregs. Pour your prepared Yeast Rinsing Water into the fermeter via the funnel. Don't worry about pouring too fast and mixing the dregs (we want to do this) but make sure you don't spill because that's annoying.

3. Once you've poured your 1.5 to 2 gallons of water onto your dregs, put some sanitized tinfoil on the top and give the fermenter some good swirls. Mix all the gunk that's stuck to the bottom up into the water and get it to break up. Aeration is okay here (oxygen will help the yeast get stronger).

4. With the sanitized tinfoil left in place allow the fermenter, with all its new water, to rest on a counter-top or table or some preferred higher place. This placement is intended for gravity purposes to allow for easy racking with your racking cane. Go flip on your SEGA or clean up the area, and allow the fermentor to settle out for 20 minutes at least. 

5. Once 20 minutes has passed, go check on your fermenter. You will notice some serious separation by this time. Depending on the style of beer, this settling process can take up to 40 minutes to get the desired result. For example, Pale Ales with their high hops levels tend to take longer to settle out. After about 20 minutes you'll be seeing four fairly distinct layers forming. 

Here are the four layers:

1. A thin, relatively clear layer at the very top. The least dense of the mix, this is diluted beer-water. Useless to us as Yeast Washers. At 20 minutes, it will be the thinnest of the layers, probably about 1/2 centimeter. As time goes on, this layer will continue to grow.  
2. The milky layer. This layer's time frame is volatile. This is the layer we are looking for! Over time, it will slowly diminish and you'll lose your window. It's milky looking because it is brimming with viable yeast.  Ideally, this layer is harvested between the 20 and 40 minute mark (which I will explain in the next process step). 
3. The third layer is tougher to find in the beginning. This layer has a slight buildup of falling particles. What happens here is, the milky layer settles into its beauty and drops all the heavy particles. This third layer is where all the heavy particles are gathering before coming together and forming the cake at the bottom.
4. The cake. This layer of visibly thick particles has a lot of yeast, but mostly it's just hop particles and dead yeast. The cake will be visible at 20 minutes: it will be a thin, discolored layer at the floor of the fermenter. It slowly gathers particles from layer 3. If you wait longer than 30 or 40 minutes to harvest, you will start to see bright white particles forming on the top layer of the cake. The white stuff is the good stuff, so get your shit together and move onto the next step.

6. Thoroughly sanitize your racking cane/hood and get mentally prepared to rack. Thoroughly sanitize one of your 1 gallon glass jugs, you will be racking layer 2 into this jug. (Note: if your hobby was harvesting human organs for sale on the black market, this would be the part where you removed the stolen organ from your captive and placed it into your Styrofoam transportation cooler). So take a deep breath, make sure you don't jiggle the racking cane around in your newly settled yeast layer complex. Tips:

• Before putting the racking cane in, lower the racking cane's rubber hood most of the way down. The idea is to apply the hood to the fermenter without allowing the cane to breach the liquid. 
• Once the hood is affixed, slowly slide the cane into the liquid up to the middle of layer 2. Use your sanitizer spray bottle to lubricate the cane so it slides gently into the yeast rinse.

7. This step requires finesse. Rack layer 2 into the gallon jug, paying careful attention to what the cane is sucking up. If you see it starting to pull up crap from layer 3, raise it up. If you've allowed it to settle for long enough, you will easily get more than a gallon of milky layer 2 transferred into your gallon jug. Sanitize the tinfoil again and place it on the gallon jug. Let the gallon jug milky yeast liquid settle for at least 20 minutes. Yes, it must settle out again! This time around when stuff is settling, you have some things to get prepared: jars and lids. 

8. Thoroughly sanitize the mason jars and their lids. Some people even boil them in water to make sure they are completely devoid of any other bacteria so that the yeast has no competition. In my experience, sanitizing works just fine. Line them up for easy pouring access and quick lid application access.

9. After 20 to 30 minutes, the same layers as before will be forming, but hopefully your layer 2 will be much bigger this time around. You can use the racking cane again but I never do. Just tip and pour slowly into your mason jars, filling each one almost to the top. If you're patient, I would suggest pouring two mason jars, then allowing the gallon jug to settle for 10 more minutes. This will allow the third layer to start to drop again and ensure that none of it is getting into your jars.

10. Apply your lids very tightly. Get them into a place in the fridge where they won't be disturbed. 

What do you do with the mason jars?

Always make a starter. You can treat these mason jars like the vials of live yeast you buy at the store. They probably have close to the same number of yeast cells as the ones at the store. Also, you can taste your starter to see if any flavors from previous batches are coming through. But don't get too optimistic: make sure you taste for off-flavors which will indicate if your culture was infected at some point. Personally, any time I've tasted a starter is always just tasted like yeast

Prepare some labels for your yeast. When labeling, list the strain, the brand, the date and the generation:

1st generation was what you bought from the store. 

2nd generation yeast is what you just harvested and will be using in your next batch. 

3rd generation would be the yeast you harvested from your 2nd generation batch, and so forth.

Irish Coffee Porter 2nd generation on left, CA Amber Ale 2nd generation on right

If you end up not using your harvest within a month, consider consolidating them into one jar. 

Consolidated

Keep tabs on which generations of yeast were used on which styles of beer. Sometimes flavors are imparted.

I was worried about the CA American Amber 2nd gens, but they worked great.

Here is a link to my original reddit.com post when I was learning how to do all this.

Most of what I've learned I got from the Internet and from talking with the technicians at the Concord Beer Beer More Beer. Thanks to Bernie_Brewer from homebrewtalk forums which i found through reddit. It started this whole yeast washing madness. Thank you to billybrew for the video that cleared everything up for me. Special thanks to /r/homebrewing.