AMS vs Acid Malt – Why Do Brewers Use Liquid Acid Instead?

If you’ve ever wondered why many UK brewers reach for liquid AMS instead of acid malt, the answer lies in a mix of brewing tradition, water chemistry, and German brewing law.

What is AMS?

AMS (often sold as CRS in the UK) is a blend of food‑grade acids, primarily sulphuric and hydrochloric acid. Its main role is to reduce water alkalinity and bring mash pH into the ideal brewing range, typically around 5.2–5.6.

In practical terms, AMS helps improve mash efficiency, hop utilisation, and overall flavour stability – especially important when brewing pale beers with alkaline UK water.

Why Acid Malt Exists

In Germany, brewers traditionally couldn’t add acids directly to beer due to the Reinheitsgebot (German Purity Law), which limited ingredients to water, malt, hops, and yeast.

To work around this, maltsters developed acidulated malt (Sauermalz). This is normal base malt that has been treated with naturally produced lactic acid via Lactobacillus fermentation. Because it is still technically ‘malt’, it remains Reinheitsgebot‑compliant.

AMS vs Acid Malt – The Practical Difference

Outside Germany, most brewers aren’t restricted by purity laws, which is why liquid AMS is so widely used in the UK. It offers fast, precise control over mash pH and is particularly effective at neutralising carbonate hardness in brewing liquor.

Acid malt, by comparison, is less precise and usually limited to 1–5% of the grist before flavour impacts become noticeable. However, it remains popular for traditional German styles where ingredient authenticity matters.

When Should You Use AMS?

AMS is ideal when brewing with hard or alkaline water, especially for pale ales, lagers, and modern hop‑forward styles. It’s quick, consistent, and easy to fine‑tune based on water reports.

When Acid Malt Makes Sense

Acid malt still has its place when brewing German lagers, wheat beers, Kölsch, or any recipe where you want to stay close to traditional methods. It also appeals to brewers who prefer pH adjustment using malt alone rather than liquid additives.

The Bottom Line

Acid malt exists largely because liquid acids were historically not permitted under German brewing law. In modern UK brewing, AMS has become the go‑to solution because it offers simplicity, precision, and reliability. Both achieve the same goal – getting your mash pH right – so the choice ultimately comes down to tradition versus convenience.