How To Filter Homebrew

Are your beers or other spirits cloudy after brewing them? If so, chances are you need to filter your drink before you can get the perfect flavor. Here’s everything you should know about how to filter cloudy beer.

Step One: Understand Beer Haze

As professionals are happy to explain, haze in beer isn’t fundamentally a bad thing. However, it is unwanted for some types of finished beer. 

That’s why knowing what beer haze is and what causes it is the first step to filtering homebrew. After all, there’s no point in using a filtering process that removes something you want.

What Is Beer Haze?

Beer haze is the collective term for any haze-producing compounds that stay in unfiltered beer and make it anything less than clear. Most experts break this down into two categories: biological and non-biological.

Biological haze is caused by yeast that actively affects the drink, especially during the brewing process. This can also occur because of bacterial contamination in beer. 

If you notice that, filtering isn’t actually the right solution to your problems. Instead, you’ll need to improve your brewing process and emphasize cleanliness throughout the process.

Non-biological haze formation in beer is mainly caused by tannins and proteins, especially when they grow dense enough to modify the appearance of your beer. These are more popular to include in some beers, especially when they can improve the flavor.

Step Two: Pick a Filter

There are many types of filters on the market, though all of them ultimately follow the same basic principle. You need a mesh that’s fine enough to block the passage of any particles you want to remove but loose enough to let the drink itself get through. 

While experts and commercial brewers can invest in more advanced beer filtration systems, homebrewing options are limited.

This is the same process that people use for filtering drinking water, and in many cases, you can use the same filters. Most household options measure filtering sizes in microns; the smaller the filter, the more it blocks out. 

In other words, a fine filter will remove more haze from beer. Whether that’s good or bad depends on the drink.

There are several major types of filters you’ll find on the market and each filter functions in slightly different ways.

Pleated Filters

Pleated filters are usually spun plastic, aggressively folded to maximize the surface area while minimizing the exterior volume. This makes them a good option in areas where space is limited; although they’re not so small, it makes a real difference for most setups.

Pleated filters force liquids from the outside to the center, where you can move them away. Ensuring a watertight seal is essential here, especially if you’re adding additional pressure to filter your drink faster.

Wound Filter

Wound filters look a lot like spools of thread, and they’re created through surprisingly similar processes. These filters wind the plastic fibers around a central spool in a somewhat irregular way.

While wound filters have their uses, they’re a poor choice for most homebrew beers because they usually come in a 20-micron rating. That’s too large to filter most things that we want to remove from beer, although you can use it as a first-stage filter in a more complicated setup.

Spun Filter

Spun filters look like long white tubes. While similar to pleated and wound filters, they don’t have quite as much surface area as pleated filters. That means you need to clean them more often. 

That isn’t a big drawback for homebrewing beer unless you’re making a lot of beer, but it’s enough of an issue that we still prefer pleated filters in most situations.

Spun filters usually block molecules down to about a five-micron rating, which is much better than wound filters.

Ceramic Filters

Finally, you might see some ceramic filters at the store. These are especially common for household water systems, including those that help remove bacteria from water. Ceramic filters are higher-quality options than pleated, wound, or spun filters. Unfortunately, they’re too good.

The issue here is that ceramic filters won’t just remove harmful things from your beer. They’ll remove good things, too, because they’re so adept at blocking almost everything except water. 

Many people make the mistake of using household ceramic filters and end up with drinks that barely deserve to be called beer, much less award-winning homebrew.

The one case where ceramic filters might be a good choice is if you’re intentionally making a light lager. Some large commercial beer breweries use ceramic filters to ensure consistent flavors in their drinks. 

Alternatively, you can filter your beer to be extremely light, then add other flavors to it, but that might violate the rules for some competitions.

What Size Filter Should I Get?

For beers, most filters should be between 1 micron and 0.5 microns. Start with a larger filter and see how that affects your drinks, then move to a smaller filter only if the first one didn’t filter enough. 

It’s easy to accidentally go too far and remove more from your beer than you want, so careful testing is essential in getting the correct filter size.

Nominal and Absolute Filters

Aside from everything above, you may see filters labeled as either nominal or absolute.

Nominal filters have pores that are roughly the average size of their official rating, which means a small percent of debris bigger than their rating will still get through. 

Some advanced brewers like using these because they can retain a little more of the original materials and flavors in a drink, so don’t dismiss them before you try them.

Absolute filters have pores that are the exact size of their efficiency rating, which generally means that nothing of that size or larger should get through. 

This means that absolute filters are objectively better at their job, but as we’ve already established, some imperfections in filtering can be a good thing.

Most filters are nominal, so you may have to go out of your way to find a good choice if you want to use an absolute filter instead.

Step Three: Prepare a CO2/Keg System

This is another place where amateur brewers often make mistakes, but it’s not hard to get things right.

While you can theoretically use a gravity-based filtering system, this can be painfully slow in any homebrew setup. The only practical way to filter drinks quickly is to push them through your system and into a keg for holding.

This, of course, presents an immediate problem. We can’t use other liquids because those will dilute a beer’s flavor, and we can’t use air because that will aerate and degrade the finished product. Vacuum-based systems are prone to failures, too.

That’s where a complete CO2 kegging system comes into play. Done well; this won’t affect the flavor of your beer too much. Alternatively, you can even use it to make carbonated beer and have a nice fizz, though some people prefer non-carbonated drinks instead.

The good news is that a proper kegging setup is easy to get online or from your preferred local store. Just make sure you clean and sanitize every part of your kegging system, including the filter housing. Some people forget to clean out hoses and tubes, and that leads to a nasty bacterial buildup in beers even after you’ve filtered them.

Finally, consider your access to replacement parts. A great system can still be a poor investment if you can’t get new pipes and filters when you need them. Try to set up something that has easy access to replacements for any component.

Assemble your keg system according to the manufacturer’s directions. If this is your first time using the system, test it out with distilled water or a similar substitute to ensure everything is alright. 

It’s common to have a few leaks when you first start, so don’t worry about those as long as you can tighten the joints and eliminate them.

Step Four: Filtering Your Beer

Once you’re all set up, it’s time actually to filter your beer.

Start by sanitizing your kegs and components as usual. Do this even if you cleaned your keg after the last time you used it. It’s always better to be careful and clean things right before you use them. Once you have some experience, this shouldn’t take long at all.

Next, transfer the beer from your fermenter into your first keg. Purge the keg with CO2, then seal it tightly. We’re moving it to a separate keg before filtering because most systems don’t work as well if you try to filter straight from the fermenter. As a bonus, you can store your beer in this first container for a while if you need to.

Once you seal the beer in the first container, sanitize your inline filter, the assembly hoses, and the keg you’ll be storing the drink in after filtering. Assemble the filter, soaking it beforehand if need be, and start adding CO2 pressure to push your beer through the filter and into the other container.

Check again for leaks while you’re doing this. You shouldn’t have anything worse than a few small gas leaks. If you see liquid leaks, stop immediately. You can probably salvage the batch, but try to keep your beer as far from oxygen as possible.

Once you’ve finished pumping successfully, remove the disconnect by the airlock first, then at the dispensing tank. The exact steps may vary slightly depending on the filtration equipment you’re using, so double-check your user’s manual as necessary.

If all went well, you should now have a keg of well-filtered, brilliant beer. Try to chill it for a little while, but don’t wait too long to test your batch and see if it worked out. If it did, you could make more batches of beer the same way. If not, adjust your filtering process as needed to improve the flavor.

Alternatives to Filtering

While filtering is a common and reliable process, it’s not the only thing you can do to clear your beer and alter its flavor. Here are some popular alternatives.

Change Your Grains

Changing grains requires brewing a new batch of beer, but changing to a lower-protein grain can remove particles from your beer and lead to a clearer product without any other modifications.

Some people use corn, wheat, or rice as alternatives during mashing, but you can try other grains if you want to be particularly creative with new types of beer. Part of the joy of homebrewing is experimenting with the process to make the perfect drink for your tastes, so it’s okay to try different things.

The main drawback to this strategy is that each grain has different requirements for use, so it’s hard to recommend one to total amateurs. Be prepared to experiment if you’re trying something particularly unusual.

Use a Wort Chiller

For those who aren’t familiar with them, wort chillers are rapid cooling systems that take a boiling beer wort below 80 degrees as quickly as possible. Most of them can manage this in less than 15 minutes, which is significantly faster than alternatives like ice baths.

Wort chillers are an excellent alternative to filtering because they change your drink fast enough to make most tannins and proteins fall to the bottom of the container. 

That makes it easy to avoid mixing them into your drink, and if they’re not in your beer to start with, there’s no need to filter them out.

Wort chillers are relatively easy to use and affordable even on amateur budgets. You can even use one alongside a filtering system to make the clearest possible beers. 

A multi-step filtering process is fine if you know how much material you’re removing from the beer.

Use a Different Yeast Strain

Did you know that yeast strains have different effects on sediment in beer? It’s true! Many homebrewers start by looking for a “good” beer yeast under some definition of the term but ignore details like the flocculation rate.

That number shows how fast the yeast cells fall out of beer after fermenting. Higher is generally better here, as it means the beer will clear far quicker. However, yeast has a significant impact on flavor, so it can be hard to find one with the right flocculation strain and the right flavor.

There’s no universal answer here because people have different tastes, so try experimenting with different yeast strains to find the one that works best for you.

Lager Your Beer

Lagering isn’t the same as using a wort chiller, though both processes rely on processing homebrew beer at the right temperature to adjust the final result. Clarifying beer through lagering usually means storing it just above freezing, usually no higher than 35 degrees, for long enough to clear the beer.

However, there are a few points to keep in mind.

If you’re bottling your drink or naturally carbonating it, you shouldn’t lager it until your beer is fully carbonated. Otherwise, you’ll kill the yeast and end up with a poorly carbonated drink. We want to avoid that sort of thing here.

If needed, you can add about half a teaspoon of rehydrated dry yeast to help fix the drink.

You’ll probably have a little sediment in the bottom of your keg or bottle of beer after lagering, but that’s acceptable as long as you don’t stir it up too much before drinking it.

Use a Fining Agent

Fining agents are an easy alternative to filtering beer, and they’re a great option if you’re in a hurry. 

However, they’re not as good as filtering the drink properly (or using a wort chiller to reduce the need for filtering), so you should only consider this route if you’re okay with sacrificing a little quality in the name of expedience.

Fining agents adhere to molecules like tannins, proteins, and yeast to make them heavier. 

Once they’ve done that, gravity pulls them to the bottom of the container and helps clear the rest of the drink. 

These usually work better in cold beer, and they’re especially effective if you combine them with a lagering process.

Frequently Asked Questions

Here are some common questions people have about how to filter homebrew.

Can You Use a Coffee Filter for Homebrew?

No. Coffee filters usually filter material to 20 microns, which is the same as a lower-quality wound filter. This makes it functionally useless when deciding how to filter homebrew, so you shouldn’t bother with it.

Worse, paper coffee filters usually can’t stand up to the pressure of a proper kegging system. They’re much more likely to tear open and let everything through, which defeats the purpose of filtering.

Finally, coffee filters work much slower than other systems. Many of them only filter a few drops of coffee at a time—far too slow for meaningful amounts of beer.

Is Hazy Beer Unsafe to Drink?

Not always. Many professional brewers have haze in their beer, and they’re proud of it, claiming it helps improve the flavor they’re creating. The main issue with hazy beer is understanding whether or not you want to keep that haze.

In most cases, a beer that smells and tastes acceptable is okay to drink. Most bacteria can’t grow well in beer to start with, so as long as you’re sanitizing things correctly, you probably don’t need to worry about haze in your beer coming from bacteria.

Try drinking unfiltered homebrew occasionally and compare it to a glass of beer you’ve filtered. There’s no substitute for experience, and making a side-by-side comparison can help you narrow down the process you want to use.

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