Introduction

Beer stone is formed from oxalates and calcium. Both of which are present in malt, plants, seeds and nuts. When consumed it causes many problems in humans and other animals, including inflammation, kidney stones and reduced bioavailability of nutrients.

This hard substance appears as a hard, off-white deposit. It can affect the taste and appearance of the beer if not properly managed. Additionally, these deposits can harbor microorganisms, leading to potential contamination issues in the beer.

Beer stone is also known to harm your brewing equipment!

Read on to learn why this happens and how to prevent it.

Why is Oxalate in Malt?

Defense Mechanism

One of the primary reasons for the presence of oxalate in seeds and nuts is as a defense mechanism. Seeds are the reproductive units of plants, and their preservation is crucial for the continuation of the species. When consumed by herbivores, the oxalate can bind to calcium and other minerals in the digestive system, reducing their bioavailability and potentially leading to nutritional deficiencies. This can deter animals from consuming large quantities of the seeds or nuts.

Calcium Regulation

Oxalate can bind to calcium to form calcium oxalate. This binding can help in regulating the levels of free calcium ions in plant cells, which is essential for various cellular processes. Seeds, being the embryonic stage of plants, have active metabolic processes and might require precise calcium regulation.

Metal Detoxification

Oxalate has the ability to chelate or bind to various metals. This can help plants sequester and detoxify potentially harmful metals, ensuring that the developing embryo in the seed is protected from toxic metal concentrations.

Energy Storage

While the primary energy storage molecules in seeds are typically fats, starches, and proteins, some researchers speculate that oxalate might also play a role in energy storage, though this is a less established idea.

Influence on Germination

The presence of oxalate influences the immediate environment around the seed during germination, potentially affecting water uptake or microbial interactions.

How and Why does Beer Stone Form?

Calcium and Oxalate Sources

The primary components of beer stone are calcium (Ca²⁺) and oxalate (C₂O₄²⁻). Calcium is naturally present in brewing water and malt. Oxalate, on the other hand, is primarily derived from the malt. During the mashing process, the breakdown of compounds in the malt releases oxalate into the wort.

Precipitation

When the concentration of calcium and oxalate ions in the beer reaches a certain level, they combine to form insoluble calcium oxalate. This compound precipitates out of the solution and adheres to surfaces, forming the hard beer stone deposits. This can ruin your equipment.

pH Influence

The pH of the beer and the brewing water can influence the solubility of calcium oxalate. In general, as the pH decreases (becomes more acidic), calcium oxalate becomes less soluble, leading to increased beer stone formation.

Temperature Influence

Cold temperatures can also promote beer stone formation. This is why beer stone is often found in equipment that is exposed to cold conditions, such as fermenters during cold crashing, beer lines in keg systems, and inside kegs themselves.

Other Factors

The presence of proteins and other organic materials in the beer can act as nucleation sites, promoting the formation and deposition of beer stone.

So now that you know what oxalates are, and that they are present in malt, what problems does beer stone influence?

The Problem with Beer Stone

There are a lot of good reasons to steer clear of beer stone. These range from making equipment impossible to clean and sanitize, destroying equipment, clogging beer lines and more.

• Contamination of Equipment

Much like a scratched plastic bucket fermenter, tiny grooves provide cover and harbor for microorganisms with the potential to infect your beer. This could also negatively impact the shelf life of your beer.

• Corrodes Equipment

When beer stone is not removed, it can cause the underlying surface to corrode. This would be a good way to destroy your expensive conical, corny keg or kettle.

• Health Problems

As mentioned earlier, when consumed, oxalate can bind to calcium and other minerals in the digestive system, reducing their bioavailability and potentially leading to nutritional deficiencies or kidney stones.

Preventing Beer Stone

There are ways to get around beer stone, preserving your own and your equipment’s health!

Regular Cleaning

This one seems like a no-brainer. Make sure to clean your beer lines and equipment often. I try to clean my lines every two weeks, or whenever changing a keg. Whichever comes first. Using an acidic sanitizer after cleaning can also dissolve beer stone.

For instance, Star San, an acidic sanitizer contains phosphoric acid, known to dissolve beer stone deposits. I typically run Alkaline Brewery Wash through my lines, followed by warm water to remove the cleaner (alkaline clean + acid sanitizer = no cleaning or sanitation!) and then Star San (phosphoric acid), which I allow to sit in the line for 10 minutes.

Use Stainless Steel Equipment

Stainless steel is non-reactive. This means it does not react to acids or many other compounds that are present in beer. Ultimately, this means less chances of beer stone forming.

Cold Crashing

We all know that cold crashing your brews causes proteins, yeast, hop particles, gelatin, tannins, and polyphenols to drop out, resulting in a really clear beer. But did you also know that this process drops out other particles like beer stone?

Hit your brew with a week-long 33F cold crash to produce insanely clear beer while also removing much of the beer stone.

pH Control

A pH that is too high contributes to the formation of beer stone, or oxalate ions binding with calcium ions.

This should not be a problem for most, since brewers aim for a pH of about 5.2 at knock-out. Finished beer also comes in quite acidic after fermentation is complete. You would only see beer stone form from alkaline water if something was very wrong with your process.

Calcium Availability

The mash is where most beer stone is formed, since that is where oxalates are released. A general rule of thumb is to ensure at least 40ppm of calcium is present in the mash to prevent its formation.

Just know that by only adding it to the mash, when we sparge the concentrations of calcium will be greatly reduced. Therefore, I decided to add just barely 40ppm of calcium to the mash, leaving only 23ppm in the finished beer.

Filtration

Much like cold crashing, fine filtration will remove most calcium oxalate crystals.

Conclusion

So, in short, clean your equipment, ensure proper pH during mashing, use an acidic sanitizer to help dissolve crystals, ensure adequate calcium availability in the mash, and make use of filtration and cold crashing to prevent beer stone!

If you do end up seeing some beer stone at any point, clean it as soon as possible so you don’t destroy your equipment.