BLACK+DECKER CM0700BZ 5-Cup Coffeemaker: Brewing Simplicity and Flavor

It’s 7 a.m. In a dorm room, an apartment, or an RV parked under a canopy of pines, a familiar ritual unfolds. A scoop of coffee grounds, a carafe filled with cool water, and the satisfying click of a single, illuminated switch. There is no touchscreen, no Wi-Fi pairing, no scheduled brew. There is only the quiet promise of coffee. Within moments, a gentle gurgling begins—a sound that, for millions, is the true start to their day. This is the world of the BLACK+DECKER CM0700BZ, a machine so simple it borders on elemental. Yet, beneath its unassuming plastic shell lies a symphony of elegant engineering, a masterclass in the science of doing one thing well. To understand this coffee maker is to appreciate the profound, unseen engineering that underpins our modern lives.

A Gurgle, a Hiss, and a Trip Back in Time

That characteristic gurgle is the machine’s heartbeat, and it tells a story of ingenious physics. Unlike more complex brewers, there is no electric pump pushing water upwards. Instead, the CM0700BZ employs a beautifully simple principle known as the thermosiphon effect. When you press that switch, you send a current through a resistive heating element, a component that operates on Joule’s first law, converting its 700 watts of electrical power directly into intense heat. This element is in contact with a small aluminum tube at the base of the machine, which holds a small amount of the water you poured into the reservoir.

The water in this tube flash-boils, creating a bubble of steam. This bubble, like a piston in an engine, forcefully pushes the slug of hot water above it up a vertical tube. As the bubble rises, it creates a partial vacuum, drawing more cool water from the reservoir into the heating tube. Gurgle. The process repeats. Hiss. A new bubble forms. Gurgle. Another pulse of water is sent skyward. It’s a self-regulating, gravity-defying pump with no moving parts, a testament to the elegance of thermodynamics.

This simple yet revolutionary process is the legacy of a transformation that began in the early 1970s. Before the invention of the first automatic drip coffeemaker, Mr. Coffee, the American home was dominated by percolators, which often boiled coffee, repeatedly forcing water through the grounds and creating a notoriously bitter brew. The automatic drip machine, by using fresh, non-boiled water for a single pass, democratized good coffee. The BLACK+DECKER CM0700BZ is a direct, unfiltered descendant of that lineage, preserving the core ingenuity while stripping away all but the essentials.

The Golden Shower and the Moment of Truth

As the hot water completes its journey, it emerges from the showerhead and rains down upon the bed of coffee grounds. This is the critical moment of extraction, and its success is almost entirely dependent on temperature. The Specialty Coffee Association (SCA) has famously defined the “Gold Cup Standard,” which stipulates that for optimal extraction, water temperature must be between 195°F and 205°F (90°C and 96°C).

This is the magic window. Below 195°F, the water is too lazy to coax out the complex, desirable flavor compounds—the bright acids, sweet esters, and nuanced aldehydes. The result is a sour, underdeveloped, “baking soda” taste. Above 205°F, the water becomes too aggressive, ripping out unwanted, bitter compounds like tannins and leading to a harsh, astringent cup. The “Optimal Brewing Temperature” touted by BLACK+DECKER is a design goal—an engineering commitment to ensure its thermosiphon system delivers water within this sacred range. It’s the machine’s attempt to solve the most critical variable in coffee chemistry before you’ve even had your first sip.

A Game of Patience and Porosity

As the dark, aromatic liquid begins to filter into the carafe, the temptation can be overwhelming. This is where the “Sneak-a-Cup” feature comes into play. It is another marvel of mechanical simplicity. At the bottom of the brew basket sits a small, spring-loaded valve. When the carafe is in place, its lid presses this valve upward, opening the pathway for coffee to flow. The moment you pull the carafe away, the spring snaps the valve shut, staunching the flow. It’s a tiny, diligent gatekeeper, granting you a 30-second window to pour a cup without creating a puddle on the hot plate.

The journey of that liquid is further defined by the filter. The included permanent mesh filter is a key factor in the final taste. Its fine pores allow the coffee’s natural oils, or lipids, to pass through into the final brew. These oils are what give coffee its body and a rich, velvety mouthfeel. For those who prefer a “cleaner” cup with more pronounced acidity, a paper filter can be used instead. The paper’s microscopic fibers are excellent at trapping these oils, resulting in a lighter-bodied coffee. The choice between them is a choice between body and clarity—a level of control over the sensory science of your brew that this simple machine quietly affords.

A Heart of Glass: The Unsung Hero

The vessel tasked with receiving the finished product is the Duralife™ glass carafe. The name itself implies resilience, and the science behind it is remarkable. Anyone who has accidentally shattered a hot glass by pouring cold liquid into it has experienced the destructive power of thermal shock. When one part of a material cools (and contracts) much faster than another, the resulting internal stress can cause it to break.

The carafe must be able to withstand being rinsed with cool water and immediately placed back onto a hot warming plate. To achieve this, it is likely crafted from borosilicate glass. Unlike standard soda-lime glass, borosilicate glass has a very low coefficient of thermal expansion. This means that when exposed to extreme temperature changes, it expands and contracts significantly less, drastically reducing internal stress. It’s the same material used to make laboratory beakers and classic PYREX bakeware for this very reason. The transparent, seemingly fragile carafe is, in fact, a piece of high-performance material science, silently doing its job under extreme conditions every morning.

The Honest Betrayal: When Good Coffee Goes Bad

Here we arrive at the machine’s most debated feature, and its most profound lesson in chemistry: the “Keep Hot” carafe plate. It is an honest feature; it keeps the coffee hot through continuous thermal conduction. However, as numerous user reviews attest, if left on for too long, the coffee develops a “burnt” taste. This is an honest betrayal.

The coffee isn’t literally burning. It’s undergoing rapid chemical degradation. The sustained heat acts as a catalyst for two destructive processes. First, the most volatile and desirable aromatic compounds—the ones responsible for that incredible smell—are boiled off and lost forever. Second, delicate compounds like chlorogenic acid begin to break down into bitter, astringent quinic and caffeic acids. The coffee doesn’t just lose its goodness; it actively creates badness.

This chemical reality is inextricably linked to the machine’s most significant design choice: there is no automatic shut-off. This is not an oversight; it is a philosophy. By omitting a timer, a complex circuit board, and the associated sensors, the design prioritizes radical simplicity, reliability, and low cost. In the world of safety engineering and UL certification, a simple heating appliance like this is permissible as long as it meets other safety criteria, placing the final responsibility squarely on the user. It’s a transparent trade-off: in exchange for an incredibly low price and fewer parts that can fail, the machine demands your mindfulness.

Final Sip: The Elegance of an Honest Machine

As you take the last sip, you realize the BLACK+DECKER CM0700BZ is not a “perfect” coffeemaker in the modern sense. It isn’t “smart.” It won’t text you when it’s done. But it is, perhaps, something more valuable: it is an honest machine. Its limitations are not hidden in complex menus but are plainly evident in its design. Its strengths lie not in a long list of features, but in the robust and elegant application of fundamental scientific principles.

In an age of over-engineered gadgets that often promise more than they deliver, there is a quiet wisdom in this simple device. It is a reminder that good design is not always about adding more, but about perfecting the essential. It’s a tribute to the thermosiphon, to borosilicate glass, to the simple valve. It is a celebration of the unseen engineering that, for the price of a few lattes, reliably delivers one of life’s most important pleasures: a good, hot cup of coffee.