The San Franciscan Roaster is a carefully constructed machine made for the purpose of roasting. As any specialty coffee aficionado is aware, roasting is an art as well as a science; this means that any alteration to the material, composition, and other variables will affect the process and the roastmaster’s ability to control or define the final roast. The makeup of our machines enhances the ability for unique roasts, which have a big impact on the final cup. It’s why our carefully crafted design has considered the architecture, the materials, and unique characteristics —such as the thickness of the drum—to create a stable thermal platform and the perfect conditions for a consistent, premium, and one-of-a-kind roast.
Why We Use Mild Steel and Not Cast Iron— Longevity and Malleability
Most coffee roasters are made out of stainless steel, cast iron, or mild steel. San Franciscan coffee roasters are built with 100% American-made steel for a variety of reasons. While cast iron has formidable heat diffusion characteristics, it is brittle by nature. In order to compensate for this fragility, the metal must be cast thickly. That is, it must have a higher mass in order to prevent it from cracking. This will create a tendency for the cast iron to retain too much heat for too long which can risk scorching the coffee beans. Our mild steel drum prevents heat from transferring all at once and allows for the greatest flexibility, heat diffusion, and heat application. This creates a slow and even heat transfer that fosters varied profiling.
Mild steel has just as good heat diffusion characteristics, transfers heat more effectively, and is more durable. Mild steel will disperse heat evenly and, due to its low-carbon composition, is also far more malleable. The malleability aspect is key, as it indicates the metal will handle expansion and contraction much better than cast iron. This is important for flexibility and range when dealing with very high temperatures.
Development Time — Enhancing the Ability to Craft the Roast
Modern roasters seek to find unique profiles that accentuate and extract the coffee bean’s natural flavors and oils. In order to do this successfully, a roastmaster will need to explore roasting time from the moment of the first crack and beyond. Development time is then an important factor in granting the roastmaster the control to manipulate the profile. Mild steel gives the best ratio of heat diffusion and the ability to apply heat with a broader range than cast iron. In other words, mild steel can cool down more quickly, as opposed to the thick and heavy mass that comes with a cast iron drum.
With older cast iron roasters, the roastmaster would be limited to certain profiles due to heat retention that prevents the slowing down of the roast and interrupts the development of the coffee. With the SFR drum roaster, if you want a longer development time, mild steel will provide the necessary flexibility to do so.
Why We Don’t Use Stainless Steel
Stainless steel does not have good heat diffusion characteristics because of its low thermal conductivity. Heat diffusion of stainless steel is simply inferior to mild steel and may require the use of double-walled drums and other conductive metals to compensate. San Franciscan Roasters uses American steel; a lot of foreign metals are recycled and thus not perfectly blended. This means they can have a different carbon makeup. Our metal is of the same consistency, a beautiful and uniform piece of metal with excellent heat diffusion characteristics. By using high quality American-made mild steel, San Franciscan Roasters offer consistency, even distribution of heat, malleability, and durability.
The Single-Walled Drum — A Gateway To More Flavor
Other coffee roaster manufacturers build their machines with a double-walled drum. And while this often provides a safety net against scorching the beans, it can significantly limit the flavor and profiling allowed with the single-walled drums.
We intentionally build our machines with a single-walled drum. We find that honey and naturally processed beans will have fruity and floral flavors bursting to get out. A double-walled drum will snuff out these wonderful flavors and dull out a lot of the potential subtleties. Our intention is to provide the artisan roaster with the broadest spectrum and palette so they can achieve the colorful flavor they seek.
Achieving the Perfect Drum Wall Thickness
The San Franciscan Roaster design and wall thickness are created and precisely measured to enable artisan roastmasters ultimate control and the ability to maintain just the right temperature for the duration of the roast. In order to achieve optimal heat diffusion, the thickness of the drum walls is calculated to be the most effective in balanced heat disbursement. For the roastmaster, this offers consistency, flexibility, and an element of control. The walls are not excessively thin that they allow for abrupt heat transfer and are not too thick that they retain too much heat at once. The precision in the metal thickness supports a longer development time and the roastmaster’s effort to experiment and explore a particular batch of beans.
Historically, early coffee roasters consisted of large cylinders and overlooked the addition of cooling mechanisms, methods, or control of smoke and heat inside the drum. As the roaster design improved, ways of controlling airflow and temperature inside the drum became a point of exploration for engineers. Today, the San Franciscan borrows from the concepts of the artisan European roasters of the late 20th century but has improved the engineering to allow for rotational velocity and the control of airflow inside the drum.
Handcrafted Ingenuity and the Aim For Infinite Possibilities
Our coffee roasters are assembled in our factory here in Carson City, Nevada, and we pride ourselves in using American mild steel with a smaller percentage of carbon. Every one of our machines is constructed using the same principles and upholding the same standards of excellent craftsmanship and architecture.
The San Franciscan coffee roasters have worked to achieve a beautifully engineered and designed roaster, where every part, every design element, and every material used has a story, a history, and a purpose. SFR aims to provide the artisan roastmaster with an incredible instrument with which they can find a broad spectrum of flavor in order to compose unique and beautiful roasts.