a.k.a. Epsom Salt

Magnesium Sulphate, commonly known as Epsom Salts, possesses an intriguing role in the brewing process. With a slight pH-lowering effect, it distinguishes itself from calcium sulphate, although its pH reduction prowess isn't as potent as that of calcium.

This versatile compound offers a unique opportunity to enhance hop bitterness, imparting a "crispness" to the character of your brew. However, moderation is key, as an excess can result in an undesirable laxative effect.

Typical concentrations for brewing water are 0 – 30 ppm Mg²⁺and 50 – 400 ppm SO₄^2-. It is also used to lower the mash pH. Additions can be put in the brewing water or directly into the mash. 

Recommended sulphate-to-chloride ratios:

4:1 – Hoppy           1:1 – Balanced          0.5:1 – Malty

1 gram of CaSO₄per liter of water contributes:

• 99 ppm Mg²⁺
• 390 ppm SO₄^2-

Calculating how much salt to add depends on the mineral levels already in solution. Contact your local water supplier for information on Ca²⁺, Mg²⁺, CO₃^2-, SO₄^2-and Cl^-in your municipal water.

Magnesium (Mg)

Magnesium holds a dual significance in brewing. While it stands as a vital yeast nutrient in modest quantities, it also contributes to water hardness, akin to calcium. Yet, its primary role remains aiding yeast development. Optimal levels range between 10-30 mg/l, supporting yeast growth. However, levels surpassing 30 mg/l can introduce a dry, astringent, or even sour bitterness to your beer's taste profile.

Sulfate (SO4) Enhancing Bitterness and More

Sulfate plays a pivotal role in accentuating hop bitterness and infusing a dry, sharp, hop-forward quality in well-hopped brews. Additionally, it contributes to pH reduction in the mash, albeit less effectively compared to carbonates due to its limited alkalinity. Care must be exercised, as elevated sulfate levels can generate an undesirable astringency. Common sulfate concentrations range between 10-50 mg/l for lighter beers, 30-70 mg/l for most ales, and even up to 130 mg/l in certain styles.

Adjusting your Water

Different styles of beer require different water profiles. Often a particular beer is associated with the water profile of the city in which the beer originated. For a listing of water profiles for popular brewing cities of the world, you can visit BeerSmiths water profile listing. If you have a target profile in mind, you can adjust your water to match that profile. You can dilute your local tap water with distilled water if some ion counts are too high for your target water profile. Similarly you can use additives to increase the level of key ions. Popular additives include table salt (NaCl), Gypsum (CaSO4), Calcium Chloride (CaCl), Epsom Salts (MgSO4), Baking Soda (NaHCO3), and Chalk (CaCO3). Unfortunately the additives do not add a straightforward amount of ions to the water profile, so its best to use some kind of water profile tool to adjust your local water supply to reach a target profile. Usually only a few grams of additives is required to achieve your target profile. BeerSmith has a water profile tool available to perform this very function. Other water profile tools are also available online.