Cassman Open Top Fermenter

Product Description & Core Philosophy

The Art of Top-Fermentation: Why Open is Better for Ales

The design of our open top fermenter is a deliberate tribute to the biological needs of ale yeast. It provides the perfect environment for these top-fermenting strains to thrive.

• Unrestricted Yeast Activity: High-temperature ale fermentation (15-25°C) produces a thick, rich krausen (a cap of yeast, protein, and hop residues). Our open design allows this krausen to rise naturally, preventing pressure buildup that can stress the yeast or clog airlocks in a sealed tank.

• Rapid Temperature Response: The open surface and single-wall construction allow for incredibly responsive temperature control. Quickly adjust your fermentation profile with simple external methods like cold water spraying or insulation wraps—20-30% faster than relying on internal cooling jackets alone.

Flavor Development: The Magic of Controlled Exposure

The true beauty of open fermentation lies in the complex, nuanced flavors it creates. This is where your beer develops its soul.

• Unique Ester & Phenol Production: Limited, controlled contact between the yeast krausen and the air stimulates the creation of desirable aromatic compounds. This is the secret to the signature banana notes (isoamyl acetate) in a Hefeweizen or the spicy, clove-like character (4-vinyl guaiacol) in a Saison.

• Krausen-Infused Aroma: The foam cap acts as a natural trap for delicate hop oils and aromatic compounds. As the krausen falls back into the beer late in fermentation, it re-infuses these flavors, resulting in a softer, more integrated, and lasting aroma profile that sealed tanks often lose through CO₂ blow-off.

Designed for the Artisan: Flexibility and Simplicity

This fermenter is built for the hands-on brewer who values flexibility and direct process control.

• Effortless Additions: Easily add yeast, dry hops, fruit purées, or spices directly into the vessel at any stage without depressurizing. It’s the ultimate tool for creative, experimental brewing.

• Intuitive Monitoring & Cleaning: Visually inspect the health of your fermentation by observing the krausen directly. When it's time to clean, the open design provides easy access, eliminating the hidden spots and shadows found in sealed tanks.

• Lower Initial Investment: With a simpler construction free of pressure-rated components (like PVRVs, pressure gauges, or seals), the initial equipment cost is 15-25% lower than a comparable sealed unitank.

Limitations and Ideal Use Cases: Is It Right for You?

The open top fermenter is a specialized tool for a specific purpose. Its "openness" is both its strength and its primary limitation.

• High Contamination Risk: Requires a highly sterile environment (clean room with filtered air) and strict sanitation protocols to prevent contamination from wild yeast or bacteria.

• CO₂ Loss: All CO₂ produced during fermentation is lost. The finished beer will require forced carbonation before packaging.

• Not for Lagers: This design is unsuitable for bottom-fermenting lager yeasts, which require a sealed, pressurized environment and low temperatures.

This fermenter is the perfect choice for:

• Product Focus: Breweries dedicated to traditional ales, wheat beers, Saisons, and Belgian styles where unique yeast character is paramount.

• Scale: Small to medium-sized operations (e.g., brewpubs, boutique craft breweries) focused on small-batch, high-variety production.

• Brand Identity: Brands that emphasize "traditional methods," "handcrafted quality," and want to offer a "visual brewing experience" for customers.

Available Configurations

While our standard fermenter line extends to 20,000L, open top fermenters are typically most effective at smaller scales where artisanal control is key. We commonly produce open top models in sizes from 100L to 2,000L. We can customize dimensions to fit your brewery's specific layout. Please inquire with our team to discuss the perfect size for your needs.

Craft Your Signature Beer 

Step away from the ordinary and embrace a brewing method that builds character, complexity, and a story into every pint.

Contact us today to discuss how a Cassman Open Top Fermenter can become the heart of your artisanal brewery.