March 20, 2019

Cleaning and Sanitizing

Some of the most frequent questions we get at Fraser Mills Brewing Supply are about cleaning for beer brewing. Beer is easily contaminated by many different organisms that exist everywhere in our homes and environment. Removing these organisms and preventing their growth is key to making great-tasting, beer. It doesn't matter how good your recipe or ingredients are, nor how much skill you have as a brewer if your beer gets infected. Cleanliness is next to goodliness.

The name's Coli, E-Coli

Everything that comes into contact with wort or beer must be both cleaned and sanitised. The important part of this is that they are two separate and distinct activities and you can't sanitise without cleaning first. That's kind of like using mouthwash without brushing your teeth. Sure the mouthwash will freshen up, but there's a layer of stuff that's hiding bacteria under it, and they'll spring into action as soon as they encounter a food source.


Cleaning is the physical removal of debris and soils from a surface. This requires cleaning agents like Aseptox, PBW, or Diversol and for speciality applications, BLC (Beer Line Cleaner) and mechanical scrubbing action.

All of the cleaners listed contain surfactants, along with either oxygen or hypochlorite and are mostly alkaline.

Surfactants are made of molecules that have two different ends. One end is strongly attracted to water; the other is attracted to dirty or oily substances. Once the surfactant latches onto a greasy yeast cell or a bio-film (more on this below) the other end seeks out water molecules and pulls the surfactant and dirt away from the equipment. This is actually much the same process as emulsification, like making mayonnaise where oil and water combine.

Oxygen and hypochlorite both work through oxidation, which breaks down stains and soils and with the added bonus that hypochlorite actually kills bacteria quite effectively, if a bit slowly and with some attendant risks (more on this below).

Alkaline solutions dissolve fats, oils and proteins. Most homebrew cleaners have a moderate alkalinity, but for a more dramatic example think of drain cleaner crystals: they dissolve clogs in no time, burning through proteins and goo.


The 'physical removal' part is critical. You can't just soak your carboys and utensils. All surfaces must be scrubbed with a soft cloth or non-scratching brush to remove film and debris.

In particular there are bio-films that accumulate on fermenters and carboys. These microscopic colloidal films are nearly impossible to see with the naked eye and are composed of the same sort of material as dental plaque in human beings. Without mechanical scrubbing they will build up to the point where they can begin harbouring spoilage organisms underneath the film, where it can affect the beer.

Every time a fermenter or carboy is emptied it must be soaked in a homebrew cleaner and then scrubbed. It can then be rinsed with clean water and either sanitised right away for use, or stored upside-down (allowing it to dry and keeping out dust and airborne organisms) to keep it ready for next use.

Some pieces of equipment are harder to scrub than others: carboys have tiny necks that limit access to their interiors. They can be cleaned with a long-handled brush, but these can scratch plastic carboys, leaving them vulnerable to colonisation by bacteria.

The easiest way to scrub the inside of carboys is to pour one or two cups of your cleaning solution into the carboy and insert a soft cloth. Gently roll the carboy so the cloth drags across the inside surface. This will provide enough friction to remove films without scratching or heavy scrubbing.

Now that your equipment is cleaned, scrubbed and rinsed, you can sanitise.


Sanitising is treating surfaces with an anti-microbial solution that kills or suppresses bacteria and spoilage organisms. Remember, you can't sanitise equipment until it has been cleaned and rinsed. Once all of the goo, debris and film is off the equipment, the surfaces will still have spoilage organisms on them that need to be killed off or suppressed so they cannot grow.

Sanitisers include BTF Iodophor, which uses free iodine to kill bacteria, Star-San, made from food-grade phosphoric acid, and Diversol, a chlorinated alkaline detergent with potassium permanganate.

Iodophor and Star San are very similar in makeup and use: mix according to the package directions, allow for two minutes of contact time and you don't have to rinse—allow to drip for another two minutes and you're done. Iodophor stains most things it touches, but is very effective.

Star San can throw people the first time they use it: it foams. It foams a lot. But the foam itself sanitises everything it touches and doesn't need to be rinsed off—as the saying goes, 'don't fear the foam'.

The only sanitiser that works as a cleaner is Diversol. It's full name is Diversol BX/A, and it comes to us from the dairy industry, where it's used to keep milk processing equipment fresh and sanitary. Because hypochlorite (the sanitising agent in Diversol) requires a minimum 20-minute contact time to kill all of the bacteria, it's can put a monkey-wrench in your brew day if you don't have time to wait for it to do the job. It's an excellent cleaner, although it has to be rinsed off with plenty of potable  water, and it will bleach clothing and other permeable surfaces on contact.

One final note: there are no home-use cleaners or sanitisers that are suitable for beer brewing. Even the most mild/pure/organic cleaners have industrial perfumes or sheeting agents that can affect your beer's taste and aroma, and some can even be toxic with long enough exposure. The right chemicals are actually quite inexpensive and will make better beer. 

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