All brewing equipment must be kept scrupulously clean. Wort-cooling, yeast-culturing, and fermenting equipment must also be made sterile. Equipment should be cleaned immediately after each use and all residues and particles washed off before it is sterilized. No abrasives should ever be used to scour brewing equipment, with the exception of copper or stainless steel kettles.
Cleaners should be used sparingly, and then only on equipment that has been badly neglected or is too soiled to be cleaned by being soaked in water and then rigorously scrubbed. Where deposits have formed, only the deposits themselves should be treated for removal, and then preferably by nothing more than a thick paste of fresh yeast.
Sterilizing with boiling water or steam is preferable to using chemical sterilants. Heating equipment to above 140 degrees F (60 degrees C) for twenty minutes eliminates most microbes, while heating to above 170 degrees F (77 degrees C), boiling, or steaming sterilizes any equipment that does not have impenetrable deposits. For homebrewers, sterilizing wet bottles and small pieces of equipment in an oven at 200 degrees F (93 degrees C) or in a dishwasher with a heat-drying cycle is oftentimes the most practical method.
Sterilizing solutions should only be applied where equipment size, shape, or manufacture — or severe contamination — makes heat sterilization impractical. The cleansers and sterilants specified below should not be misconstrued as being substitutes for prompt and thorough cleaning with hot water or sterilizing with pure, clear 180 degree F (82 degrees C) water. All cleaning and antiseptic solutions should be freshly made up as needed, as most lose their potency during storage.
A thorough rinsing after using a cleanser or sterilant is very important to protect the taste of the beer. Spray or swab all surfaces with rinse water. Grossly inefficient rinsing can be identified by monitoring the pH of the rinse water for change.
The usual cleaning cycle includes a cold-water soaking, either a hot or cold cleaning as appropriate, and a cold rinse. For fermenting equipment, heat sterilization or the application of a sterilant (usually in cold water, followed by a hot rinse) is also necessary. See “Percentage Solutions” in the “Useful Information” section of appendix D for the preparation of percentage solutions. Following is a detailed look at how to clean various materials with different solutions.
Stainless steel: Clean with 2 to 3 percent hot caustic-soda solution and mild detergent at 170 degrees F (77 degrees C), followed with one or more rinses with water hotter than 140 degrees F (60 degrees C). Use 2 percent phosphoric, sulfuric, or sulfurous acid or 3 percent iodophor as a sterilant. Acid sterilants remove beerstone, or deposits of oxalic lime and organic matter and passivate stainless steel.
Copper: Only noncorrosive cleansers should be used. Caustic soda especially must be avoided. As copper is commonly used only for kettle fabrication, it should only need to be scoured with sand or other silica abrasive.
Glass, glazed porcelain: Most cleansers and sterilants are suitable for use on glass or glazed porcelain; only phosphoric acid should not be used, as it can etch glass. A 2 to 3 percent caustic-soda solution is the preferred cleanser. Trisodium phosphate or mild detergents may be substituted. Microorganic contamination may be countered by application of chlorinated trisodium phosphate, or more commonly by a subsequent sterilant application. Household bleach in .2 percent aqueous solution is the most commonly used sterilant, but after a clear rinse, any of the acid sterilants can be used.
Plastics, enamelware: A 2 to 3 percent caustic-soda solution will not harm these surfaces, but mild detergents are more commonly used. Either material requires application of a cleanser more frequently than glass or metal surfaces. Sterilants may be .2 percent chlorine bleach, 5 percent chlorinated trisodium phosphate solution (alkaline), sodium or potassium metabisulfite, 2 to 3 percent phosphoric acid, or 3 percent iodophor (acid).
Aluminum: Only mild detergent with an acid cleanser (2 to 5 percent nitric or phosphoric acid) should be used. Compatible sterilizing agents include nitric and sulfurous acid.
Wood: Rinse and brush wooden articles and then immerse them in boiling water immediately after use. Because of wood’s natural porosity, use of cleansers should be avoided. Where absolutely necessary, a hot 2 to 3 percent solution of caustic soda or 5 percent sodium carbonate or bicarbonate can be applied, but it must be rinsed away by several long baths, from hot to cold. Five percent metabisulfite sterilizing followed by several clear-water rinses may be employed, but boiling or steaming is preferred. Any solution applied to wood is likely to leach into it, and is very difficult to coax back out of it.
Do not let wood implements sit damp between brewings. They must be dried thoroughly after cleansing.
Malt mills and screen: These need only be cleaned with a stiff brush after every use. The cleaning, however, should be thorough.
Mash and lauter-tuns: These should be kept wet after use and then scrubbed clean, rinsed, and dried. A false bottom, strainmaster, or grain bag in the tuns must at least occasionally be boiled in a 2 to 3 percent caustic-soda solution or be scrubbed with an appropriate cleanser.
Brew kettles of copper, stainless steel, or aluminum: Articles of this construction are the only ones used in brewing upon which an abrasive should be used. In fact, they benefit by its employment. The abrasives not only scour away calcified deposits, but pitting and etching of the kettle surface improves heat transfer and protein coagulation during wort boiling. A thick paste of fresh yeast should be brushed onto any stubborn deposits and kept moist before scrubbing. The yeast is finally rinsed away with clean, cold water.
Immersible heating elements: These must periodically be soaked in 10 percent trisodium phosphate solution and then scrubbed to remove scale.
Fermentation locks: The locks should always be soaked in a detergent or caustic-soda solution and then flushed clean after every use. Use of an antiseptic solution in the fermentation lock is not necessary, but it is advisable. A fermentation lock should be changed as soon as it becomes dirty.
Fermenters: Insofar as possible, fermenters should only be cleaned by a thorough brushing in cold water after use and then be heat sterilized before their next use. Any beerstone deposits that do not come free should be covered with yeast paste. A mild detergent or cleanser (3 percent caustic soda, 5 percent trisodium phosphate, or 2 percent nitric or phosphoric acid) may be added. The paste should be kept moist for a day and then the deposit scrubbed away. Where a cleanser is necessary, use caustic soda. Where a sterilant is necessary, use household bleach, 2 to 3 percent phosphoric acid, or 1 percent iodophor.
Plastic tubing: Used for wort cooling or siphoning, plastic tubes should be boiled in caustic soda and thoroughly flushed. Hydrogen peroxide can also be used to clean and sterilize tubing very effectively. Storing tubing in a sterilant solution largely eliminates the risk of contamination, but bleach turns tubing opaque, and iodophor discolors it, although this is not a serious problem to most brewers.
Bottles: Clean-looking bottles can be washed in 170 degree F (77 degrees C) water, boiled, or steamed. Dirty bottles should be soaked and then scoured with 2 to 3 percent caustic soda, 5 percent trisodium phosphate, or a mild detergent solution, followed by several rinses with water hotter than 140 degrees F (60 degrees C).
Sodium hydroxide: Caustic soda, NaOH. It is effective only when it is used hot. A most effective solvent, it hydrolyzes most malt and wort residues. It may, however, leave calcium salt residues, except when it is applied with a detergent or the sequestering agent EDTA (C10H12N2Na4O8). It is highly corrosive and should not be used on copper or aluminum surfaces. It dissolves skin and burns mucous membranes; use only with rubber gloves and adequate eye protection. Potassium hydroxide gives the same results.
Sodium carbonate: Washing soda, Na2CO3⋅10H2O. It is applied hot. It is far less effective than other cleansers mentioned.
Sodium bicarbonate: Commonly called baking soda, NaHCO3, similar to sodium carbonate in effect.
Trisodium phosphate: A common household cleanser, TSP, Na3PO4⋅12H2O, is a very effective solvent, especially for calcified deposits such as boiler scale. Chlorinated trisodium phosphate adds some bactericidal capability to its cleansing.
Nitric acid: Called aqua fortis, HNO3, this substance is caustic but does not corrode aluminum. It is corrosive to other metals. It can also be used as a sterilant, or to passivate steel.
Phosphoric acid: Phosphoric acid, H3PO4, is a very effective bactericide at below pH 3.0 (2 to 3 percent solution). It passivates steel, dissolving scale deposits and protecting it from oxidation. It is a substitute for nitric acid when cleaning aluminum. Do not use on porcelain.
Sodium hypochlorite: Common household chlorine bleach, Chlorox, or chlorinated soda, NAClO⋅5H2O. It is a very effective sterilant. It is usually used in strengths less than 1 percent in aqueous solution, but it is effective in distilled water at less than .05 percent (.3 fluid ounce in five gallons) with reasonable contact time. Usual dilution is .2 percent/one fluid ounce in four gallons; at this concentration, the sterilant does not need to be rinsed, so long as objects are well drained.
Caution: This cleanser produces poisonous chlorine gas in contact with acid compounds. This reaction also strongly corrodes stainless steel.
Iodophor: Iodine combined with phosphoric acid. One-half fluid ounce of iodophor per gallon of solution (four milliliters/liter) is an effective sterilant with thirty minutes’ contact time at below 120 degrees F (49 degrees C). At this concentration it does not require rinsing.
Phosphoric acid: A commonly used acid sterilant. It is very effective at 2 to 3 percent concentration (pH 2.0 to 3.0), and residues at this strength may not mar beer flavor. Phosphoric acid passivates stainless steel against corrosion.
Hydrogen peroxide: H2O2 is an oxidizing sterilant that is also a very effective solvent for cleaning flexible tubing in 2 to 3 percent solution.
Sodium metabisulfite: Na2S2O5 is antifermentive, not bactericidal. In the presence of acids, it produces noxious sulfur dioxide (burnt-match) odor. It is not widely favored by brewers as a sterilant.
Potassium metabisulfite: K2S2O5 is similar to the sodium salt.
Calcium sulfite: CaSO3⋅2H2O was once commonly used by commercial breweries. In contact with the atmosphere, it oxidizes to CaSO4.
Sulfuric acid: Sulfuric acid, H2SO4, is corrosive to most metals. As sulfurous acid, SO2, it is commonly used in commercial breweries in 6 percent aqueous solution.
Alcohol, ethyl or isopropyl: This is useful only for sterilizing small articles. It is effective only with reasonable contact time.
Quaternary ammonium sterilants: Should be avoided, as the residues from these compounds negatively affect foam retention.