This week I look at the Sulfate to Chloride ratio and how it can have a significant impact on the perceived bitterness of your beer. In fact, it is probably second only to mash pH when we discuss the flavor impacts of water as a beer ingredient.
The Sulfate to Chloride Ratio
Chloride ions tend to enhance the malty aspects of beer, as well as enhance the perception of mouthfeel. Chloride concentrations in excess of 200 ppm in particular tend to give a full malty taste. Sulfate ions, in contrast, tend to accentuate hop flavors and bitternes, often leading to the perception of a drier and cleaner finish. Sulfate levels above 200 ppm are best reserved for hoppy beers like IPAs.
The Sulfate to Chloride ratio can be stated simply as the ratio of sulfate (SO4) ions (in ppm or mg/l) to the concentration of Chloride (Cl) ions. You simply divide sulfate by the chloride ion concentration. A ratio of around 1:1 (or 1.0) is considered balanced in that the water will neither enhance the malt or hop flavor. Ratios below 1 tend to lend more malt character and those above 1 tend to enhance the hop character of a beer. Note that some references have it listed as “Chloride to Sulfate ratio” which is basically the same measure but inverted.
Understanding Sulfate to Chloride Ratios
John Palmer and Colin Kaminski cover the ratio in their book Water: A Comprehensive Guide for Brewers (Amazon affiliate link) on p149. They mention that a prerequisite for using the ratio is that some modest level of both sulfate and chloride must be in the water to start with. Typically brewing water has 50-250 ppm of sulfate and 0-250 ppm of chloride. They also note that the potential strategy of maximizing both sulfate and chloride at the same time to emphasize both malt and hops does not work. Excessively high sulfate and chloride levels at the same time lead to harsh flavors. For example a ratio of 30 ppm to 30 ppm is not at all the same as a ratio of 300 ppm to 300 ppm.
They define the useful ratio range as roughly 0.5 to 9, as beyond that you are often working with a sulfate or chloride level that is too high or low for use in beer. They suggest a minimum threshold of chloride of roughly 50 ppm before you can affect the flavor of the beer, and a similar minimum of 50 ppm for sulfate. Noble hops and light lagers tend to be more sensitive to sulfate levels, and sulfate levels below 100 are recommended for these beers. Ales can often withstand higher levels of sulfates.
John Palmer also published a water spreadsheet with guidelines for the ratio. A summary is below:
- 0-0.4: Too Malty
- 0.4-0.6: Very Malty
- 0.6-0.8: Malty
- 0.8-1.5: Balanced
- 1.5-2.0: Slightly Bitter
- 2-4: Bitter
- 4-9: Very bitter
- 9+: Too bitter!
Looking at the above table you may want to target a ratio in the 4-7 range if you are brewing an IPA for example, while for a malty German Lager you would want to instead target something in the 0.4-0.6 range while keeping the overall sulfate levels low. Excessive levels of either sulfate or chlorise can be harsh.
You can add more chloride to your water by adding Calcium Chloride (CaCL2), and you can add sulfate by adding Gypsum (Calcium Sulfate or CaSO4). Go light on the water additions, however, as it does not take many grams to significantly change the water content. You can use a number of online spreadsheets or the Water Profile Tool in BeerSmith to calculate the effects of your additions.
Related Beer Brewing Articles from BeerSmith:
- Brewing Water – Hard or Soft?
- Mash pH – Hard Water Treatment for Brewing Beer
- Beer Water Testing with Christian Krzykwa – BeerSmith Podcast #118
- Balancing your Beer with the Bitterness Ratio
- Sweet Stout and Milk Stout Recipes
- Five Critical Tools for Beer Recipe Design
- Phenolics and Tannins in Home Brewed Beer
- Caramel and Crystal Malt in Beer Brewing