Brew Tips: Chlorine Removal with Campden Tablets

One of the ongoing topics I would like to cover are brewing tips.  These will be miscellaneous things I have found to make my brewing better and easier.

Unless you use bottled water for brewing (and maybe even if you do), chances are you have chlorine or chloramine in your brewing water.  Chlorine will dissipate from the water if you leave the water out overnight or over a day or two, and is relatively easily filtered out if run slowly through a carbon filter.  Chloramine, on the other hand, is actually ammonia with some of the hydrogen atoms swapped out for chlorine, and is extremely persistent.  It will not dissipate (at least not in the amount of time you are going to want to give it), and its practically impossible to filter out of the water.  Unfortunately, it can still react with things in your beer such as phenols to create chlorophenols.  Chlorophenols can be detected by the human tongue at extremely low levels (as in parts-per-billion), and taste terrible- some are described as band-aid-y.  So, what to do?  Campden tablets to the rescue.

Campden tablets are potassium metabisulphite or sodium metabisulphite.  The active ingredient is sulfur dioxide, and is normally used to inhibit yeast growth in wine or mead.  But, it also reacts with chlorine and chloramine.  Used in dosages of 1 tablet in 20 gallons (76 L), the sulfur dioxide will more or less completely react with the chlorine compounds in the water, causing them to dissipate.  This dosage was calculated (not by me) for the maximum amount of chlorine allowable in water in the US supply, so depending on where you live you can likely get away with less.

Campden tablets in water for water treatment

So, whats the best way to get the proper dosage for a five gallon batch (or however much you need with strike water)?  Dissolve the tablet in 2 cups of water, and you will need a half-cup of solution per five gallons of water, or 1.6 tbsp per gallon.  Alternately, dissolve 1 tablet in 0.5 L of water and you’ll need about 6.6 mL per L you use in your brewing.

A quick note to those who are also looking into water treatment: Campden tablets will not react with chloride, an ion important to brewing, so no worries.  For those that don’t know what I am talking about, stay tuned- I eventually hope to do a post (or lots) on water treatment (UPDATE: here they are).  Some people are allergic to sulphites.  If you can’t drink wine without getting a headache (I mean a few sips, not the bottle), you might want to stay away from using them.  But, at the extremely low dosages left after the reactions, you are probably fine.

[2013.10.22 UPDATE: Here is a useful table for those paying attention to water treatment.  Basically, the reaction of the campden tablet with the chlorine/ chloramine will add a small amount of sulfate and chloride, and slightly reduce alkalinity.  The numbers in the table are equivalent to ppm.  Given that the total amount of chlorine and chloramine is very rarely above 3 ppm (and usually lower), the total change will be small, and can probably be ignored when calculating water treatment additions.  Many parts of Europe use ozone instead of chlorine compounds, and do not have this issue at all.

Changes in ion concentrations from Campden tablet addition.

This table was put together by AJ Delange.  It comes originally from a paper he wrote, which can be found at http://hbd.org/ajdelange/Brewing_articles/BT_Chlorine.pdf (thanks to Antony for the find); it can also be found in Water: A Comprehensive Guide for Brewers, Palmer and Kaminski.]

– Dennis
Life, Fermented

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