What is beer stone (and how to prevent it)?

Beerstone, identified in scientific terms as calcium oxalate, represents a formidable obstacle within the realm of beer production. This problematic compound emerges as an inadvertent byproduct throughout the brewing cycle, predominantly accumulating on the surfaces of brewing apparatus that are exposed to wort—the nutrient-rich liquid derived from the mashing stage—and the beer itself.

The implications of beerstone accumulation are far-reaching, affecting not only the operational efficiency and hygiene of brewing facilities but also impinging upon the sensory quality and safety of the final beer product.

Consequently, a deep-seated understanding of how beerstone forms, alongside a comprehensive exploration of effective strategies for its eradication and prevention, is paramount. This knowledge not only aids in safeguarding the integrity and flavor profile of the beer but also ensures the longevity and optimal performance of brewing equipment, thereby upholding industry standards and consumer expectations.

The Formation of Beerstone

The scientific underpinnings of beerstone formation in the brewing context revolve around the precipitation of calcium oxalate (CaC_2O_4), a compound that arises from the interaction of calcium (Ca^2+) and oxalate (C_2O_4^2−) ions. These ions find their source in the water used for brewing, as well as the raw materials, namely grains and hops. 

Calcium ions are naturally prevalent in water, particularly in regions with hard water, contributing to the mineral content that can influence beer flavor. 

Oxalate ions, on the other hand, are primarily produced during the breakdown of organic compounds within hops and grains throughout the mashing process. 

When these two ions come into contact under the right conditions, they react to form calcium oxalate, a process that can be summarized by the chemical equation:

${\text{Ca}}^{2+}(��)+{\text{C}}_2{\text{O}}_4^{2-}(��)\to {\text{CaC}}_2{\text{O}}_4(�)$

This reaction leads to the formation of solid calcium oxalate, which is sparingly soluble in water, causing it to precipitate and adhere to surfaces as beerstone. The crystalline nature of beerstone makes it particularly tenacious, forming a hard layer on brewing equipment that is difficult to remove without specific interventions.

Understanding the conditions that favor beerstone formation is crucial for its prevention and removal.

The solubility of calcium oxalate in water is highly dependent on the pH and temperature of the solution. During the brewing process, variations in pH and temperature can significantly affect the solubility of calcium oxalate, with lower temperatures and higher pH levels promoting its precipitation. 

This is particularly relevant during the cooling and fermentation stages, where conditions can become conducive to beerstone formation.

Furthermore, the presence of nucleation sites, such as rough surfaces or existing beerstone deposits, can facilitate the aggregation of calcium oxalate crystals, exacerbating the problem. By understanding these scientific principles, breweries can adopt strategies that minimize the conditions conducive to beerstone formation, such as controlling the pH and temperature of the brewing process, and ensuring smooth, clean surfaces on brewing equipment to reduce nucleation sites.

Impact on Brewing Equipment and Beer Quality

Beerstone's presence poses several challenges in the brewing process. First and foremost, it creates a rough surface that can harbor bacteria and wild yeast, leading to contamination and spoilage of beer. This contamination risk undermines the beer's quality, flavor, and safety. 

Additionally, beerstone build-up can reduce the efficiency of heat transfer in brewing equipment, leading to increased energy costs and potential process inefficiencies. The aesthetic appearance of brewing equipment can also be negatively affected, which may be a concern in breweries where visual appeal is part of the customer experience.

Strategies for Removing Beerstone

Chemical Removal Expanded

Chemical removal remains the cornerstone of combating beerstone accumulation in brewing operations. The effectiveness of acidic solutions in this context hinges on their ability to chelate calcium ions and dissolve oxalate ions, thereby disintegrating the calcium oxalate matrix. Phosphoric acid, for instance, not only dissolves beerstone but also passivates stainless steel surfaces, offering a degree of protection against future corrosion. Nitric acid, another potent option, provides additional antimicrobial benefits, helping to sanitize surfaces as it cleans.

 
When employing these acids, it's imperative to understand their reaction mechanisms:

• Phosphoric Acid: ${\text{CaC}}_2{\text{O}}_4+2{\text{H}}_3{\text{PO}}_4\to {\text{Ca}}^{2+}+2{\text{HC}}_2{\text{O}}_4^{-}+2{\text{H}}_2{\text{PO}}_4^{-}$

• Nitric Acid: ${\text{CaC}}_2{\text{O}}_4+2{\text{HNO}}_3\to {\text{Ca}}^{2+}+2{\text{C}}_2{\text{O}}_4^{2-}+2{\text{NO}}_2+{\text{H}}_2\text{O}$

The nuanced approach to using these acids ensures the dissolution of beerstone without compromising equipment integrity. It’s crucial for breweries to meticulously adhere to specified concentrations and exposure times, as overly aggressive chemical treatments can damage equipment surfaces or pose safety risks to personnel. Mechanical Removal in Depth
Mechanical methods for beerstone removal offer a straightforward, albeit physically demanding, approach.

Manual scrubbing with abrasive pads or brushes can physically dislodge beerstone deposits, but this method requires significant labor and may not reach all surfaces effectively. High-pressure water jets elevate this approach by using forceful streams of water to blast away residues, including beerstone.

This method's efficacy is particularly noted for external surfaces and large, accessible areas of brewing vessels. However, the limitation lies in its inability to adequately clean intricate or internal components, where direct physical access is restricted.

Ultrasonic Cleaning: A Modern Approach Ultrasonic cleaning represents a leap forward in brewery maintenance technology. By generating high-frequency sound waves (typically in the range of 20-40 kHz), this method induces cavitation in the liquid medium. Cavitation bubbles form and collapse with immense energy, producing shockwaves that effectively dislodge beerstone deposits at a microscopic level. This method's advantage lies in its non-invasive nature, allowing for the cleaning of complex geometries and sensitive components without physical contact. 

The efficacy of ultrasonic cleaning in removing beerstone not only underscores its potential as a stand-alone solution but also as a complementary technique to chemical and mechanical methods, ensuring thorough decontamination of brewing equipment. Preventing beer stone is the best treatment....

Prevention is invariably more efficient than cure, particularly in the context of beerstone management. Establishing rigorous cleaning and sanitization protocols is foundational, but optimizing water chemistry plays a pivotal role as well.

Implementing water softening systems can significantly reduce the concentrations of calcium and magnesium ions, directly impacting the potential for calcium oxalate formation. Moreover, controlling the brewing process to minimize oxalate levels, through careful selection of raw materials and process adjustments, can further mitigate the risk of beerstone accumulation.

These preventive strategies, combined with regular equipment inspections and maintenance, form a comprehensive approach to preserving brewery operations' efficiency, safety, and product quality.


Beerstone is a complex issue within the brewing industry, stemming from the interaction of brewing ingredients and process conditions. Its impact on equipment efficiency, beer quality, and safety underscores the importance of effective removal and prevention strategies. Through a combination of chemical, mechanical, and innovative cleaning methods, alongside preventive measures, breweries can effectively manage beerstone, ensuring the production of high-quality beer. Engaging in ongoing research and adopting best practices for brewery maintenance are essential for addressing the challenges posed by beerstone.

beerstone, kegs, kettle, PBW, sanitization