The brewing process for hard seltzer is super quick and and easy.  I've listed my process below along with a few important things to consider before brewing your first batch.

Water:  There is quite a bit of discussion on water for hard seltzer, mainly around the clarity of the finished product.  I use filtered tap water for my seltzers, and I haven't had any issues with doing that.  If you choose to use RO or Distilled water, you may need to add some brewing salts back in, depending on how much you get into water chemistry.

Yeast Nutrient:  Since you are only fermenting sugar and water, the yeast will want/need a little help to get going.  I'm lazy, so I only add yeast nutrient & energizer to the seltzer in the kettle.  Others have had good luck with staggered nutrient additions, which have really caught on in the mead world over the last few years.  That requires buying different types of nutrients and adding them over the course of a few days when fermentation is first starting off.  Both methods will result in a good seltzer, so do some experimenting and see what works for you.

Flavoring:  There are several different flavoring options for hard seltzer.  I've experimented with the standard beer fruit flavorings (usually made by Brewers Best (BB)) as well some Amoretti Craft Puree, which adds a really fresh and bright fruit flavor.  Both have their benefits and drawbacks.  The BB flavorings are relatively inexpensive, but some are better than others.  I find the Cherry to be very artificial tasting, and the Peach tastes more like canned peaches rather than fresh.  The Amoretti has really great and fresh fruit flavor, but the cost is around 4-5 times that of the BB option.  I have been experimenting with the BB flavors at kegging, and then adding a splash of the Amoretti Craft Puree to each glass if I think the batch needs more flavor.  As I dial in what BB extracts I like and in what volume and combination, I will probably use less of the Amoretti, but it all depends on what I'm looking for.  I would suggest trying both and seeing what your preference is, or go with a combination as I have been doing.

Yeast:  Yeast varieties for Seltzers have changed as more and more brewers (home & professional) have started experimenting with brewing seltzers.  A lot of people initially used wine yeast, but it appears the new go-to yeast is the fast-fermenting Kveik yeast, specifically the super neutral Lutra variant. 

Clarity & Flavor Reduction - Activated Carbon & Carbon Filtering (NEW):  Given time, the yeast will drop out of suspension and you should be left with a crystal clear seltzer.  It took me a couple batches to figure out that wine yeast flocculates (drops out) much slower than ale yeast. I found it took at least 3 weeks to achieve clarity without going through any other measures.  That's why some of my first batches were a bit cloudy, even though they reached their final gravity.  I also noticed a slight fruity ester from the yeast that was always in the background.  After reading through an article in Zymurgy magazine about brewing hard seltzer at home, I noticed they recommended the use of activated carbon to help strip additional yeast and fermentation character out of the final seltzer.  I've added a section to the site below that goes through the process I followed in more detail in case you want to try it on your seltzer at home.  I was VERY happy with the results!

Ingredients:

• 4lb Table Sugar

• 2 tsp Yeast Nutrient

• 2 tsp Yeast Energizer

• 1-2 packs yeast (71-B, Kveik, or other neutral variety)

• 1-2 TB Lemon Juice (optional)

Brewing Process:

1. Bring 1-2 gallons of water to a boil along with the 4lbs of table sugar.  Make sure to stir the pot frequently until the sugar is totally dissolved.  Alternatively, you could bring just the water to a boil and add the sugar off heat, stir to mix, and add it back to the heat.

2. Boil for 5 minutes and turn off the heat.

3. Add Yeast Energizer & Yeast Nutrient (and lemon juice if you're using) and stir to combine.

4. Chill in a water bath or other chilling method until the temp is around 80-85 degrees.

5. Add the chilled sugar water to your sanitized fermenter and top up to 5 gallons with cold filtered tap water or RO/Distilled.

6. Sprinkle on yeast, mix and aerate (I use a mix-n-stir), attach lid & airlock, and wait.  Fermentation seems to take a little longer with wine yeast, so give it a couple weeks before taking a gravity reading.

7. Aerate & degas once or twice a day for the first 3 days or so.  This helps speed up the fermentation and reduce some of the perceived yeast aromas I was noticing post-fermentation.

Kegging:

This is where I will add the Brewers Best (or other) flavoring to the keg and rack the seltzer on top of the flavoring to mix.  I've found that 4-6 oz of BB extract is about right for me, depending on the flavor(s) being used.  This is where you can experiment with blending different flavors, brands, and amounts to see what works best for you.  I would start with less flavoring than you think, then rack the seltzer onto the flavor, and try it again before you're done.  For carbonation, I just use the standard process, pressure, and temp as with my beer.  I find that the carbonation isn't quite as high as commercial brands, but that's not necessarily a bad thing, since those tend to make me burp a ton.  If you have a dual-pressure regulator, you can try a higher pressure to see what you prefer.

Activated Carbon - My first few batches of seltzer were a bit cloudy, and they definitely had some residual fruity and slight sulfur flavors & aromas.  The fruit flavoring additions did a good job of masking these flavors, but I wanted to work on trying to get rid of them before kegging.  My first attempt to improve clarity was to use Activated Carbon in the secondary fermenter based on some initial online searching.  This worked pretty well, but some of the fermentation character was still coming through in the final seltzer.  Here's the process I follow to add Active Carbon to my seltzers:

1. Clean & sanitize a secondary fermenter

2.  Add 1-2 TB of Active Carbon (AC) to the bottom of the fermenter

3.  Rack seltzer on top of AC to mix

4.  Allow the seltzer to sit for a week or two before proceeding to carbon filtering (below) or kegging

Carbon Filtering - With some residual fermentation character still coming through after trying to use Active Carbon in secondary, I decided to try pushing my finished seltzer through a whole-house carbon filter by jumping from one keg to another, and that was a game changer!  After filtration, the seltzer was almost as neutral as water, with all those fermentation characters completely removed.  I likely don't need to use the activated carbon in secondary, but it isn't doing any harm, so I'm going to keep using that along with carbon filtering to achieve a very neutral finished product.  Since this process requires prepping and sanitizing more equipment, I usually like to filter more than one batch of seltzer at one time if possible.  Here's the process I follow for carbon filtering my seltzers before flavoring in the keg:

1.  Clean and sanitize a keg for the pre-filtered seltzer and however many kegs you plan to keg as well

2.  Rack seltzer over to pre-filtration keg, attach lid, add CO2 & vent headspace

3.  Attach filter with quick disconnects to the pre-filtered keg and the post-filtered keg, and make sure the direction of flow on your filter is going the correct way

4.  Open the post-filtered keg pressure release valve to allow the keg to be filled with the filtered seltzer

5.  Apply 5-10 PSI of CO2 to the pre-filtered keg and monitor the flow through the carbon filter.  You want around 1 gallon or less of seltzer to be passing through the filter every minute.

6.  Repeat with second keg, or disconnect equipment and thoroually clean the filter housing, filter, and tubing

Recipes:

Here are a few links to the Hard Seltzers I've made so far.  I'll keep adding more as I go along on my Brew Log page, so check that out for updated recipes, processes, and ideas.

• Hard Seltzer (Multi-Berry)

• Hard Seltzer (Multi-Berry2)

• Hard Seltzer (Blackberry)

• Hard Seltzer (Mango)

Future Seltzer Ideas: 

• Double Batch & Dilute:  After talking with some pro brewers and fellow homebrewers that are making Hard Seltzer, they seem to be brewing higher gravity/double batches of seltzer and then diluting them with water post-fermentation.  I like this idea for a couple reasons.  First being that you can brew two (or more) batches of seltzer using only one fermenter, as well as the time savings.  The second would be potentially reducing the amount of esters that I've noticed after fermentation completes. If I brew a double batch and then dilute with water, I would assume the overall yeast character should be diluted as well and result in a more clean tasting alcohol base for the fruit.  I'll be giving this a try on my next batch to see how it comes out.  As part of that experiment, I will also be using tap water to dilute one half, and distilled on the other to see if I notice any differences.

• Different Fruit Flavorings:  A few of our homebrew club members have tried what appear to be vaping flavorings on both their beers and seltzers, and have had good luck with the Wizard Labs brand.  One thing they all mentioned is that these flavorings are VERY CONCENTRATED, and only require a few drops for a whole 5-gallon batch.  This kind of scares me a bit, but I may need to order a few and try them out.  The prices seems very reasonable for how much flavor they're supposed to add.

• Vodka "Seltzer" - Several companies have started releasing vodka-based "seltzers" or ready-mix beverages.  This takes the brewing aspect out of things, but it would still be interesting to play around with.  If you can get some cheap vodka from Sam's Club or Costco, it may be worth a try, but it would definitely be more expensive than just fermenting sugar.  Brulosophy did a great write-up on the process for making a vodka seltzer HERE.

• https://byo.com/article/hard-seltzer-made-easy/

• https://brewtogether.com/2019/10/20/homebrewing-hard-seltzer/

• https://brewchatter.com/blogs/brewchatter-homebrewing-blog/the-ultimate-guide-to-homebrewing-hard-seltzer

Amoretti Craft Puree - Use to flavor the seltzer per glass or the whole batch:

• https://amoretti.com/collections/craft-purees

Amoretti