It has no switches or knobs. To maintain the smooth one-piece look and eliminate moving parts, the start brew switch is touch sensitive. Similarly the carafe has a cork bottom with embedded magnet that the base unit uses to detect if the carafe is absent or if it's removed mid-brew. If your appreciation of art leans to minimalism, the Ratio is certain to complement your kitchen decor.
The above "press packet" photo captures the Ratio's simple lines and uncluttered fascia, but belies the brewer's unusual height (14" or almost 2" taller than the Bonavita BV1900TS). Most US cabinets are 17.5 to 18" above the countertop; the photo below shows the Ratio Eight next to the Baratza Forte below a cabinet with 18" of clearance:
Of course there's still more than enough clearance above the brewer; the above comparison is simply to show that while the Ratio Eight borders on a modern kitchen's objet d'art, like the typical fashion model, it's noticeably taller than its less striking contemporaries.
As the name implies, proper coffee extraction requires a proper ratio of water to coffee (and of course, proper grind setting). The Ratio water reservoir has halfway and full line marks, though I recommend weighing the water/coffee, as it's easy to under or overshoot the desired water amount by going a smidge above or below the line. If you use a scale, remember to allow for the weight of the carafe itself. I use a Bonavita 3KG scale, though there's plenty of scales that can do the job recommended in the forums. The SCAA recommends a 18-to-1 ratio of coffee to water (or more precisely, 55 grams of ground coffee per liter). Although the scale is optional, of course a grinder isn't. For the tests at home, I use a Baratza Forte.
The Ratio includes a KONE permanent filter; it you prefer, it accepts paper filters, as does any Chemex brewer. The grind setting on the Forte was Macro = as coarse as it goes. The micro setting was adjusted such that the water collected on the bed of coffee but didn't overflow. For the coffees tested, I started around the midpoint of the micro setting and adjusted a couple notches. The brewing begins with a brief bloom phase where a small amount of water saturates the coffee bed then waits while the grounds expands; the brewing phase follows shortly thereafter. The full cycle is automatic and takes only a few minutes. The slowly bubbling water column in the reservoir offers a little coffee theater as it progresses.
Below is an excerpt from the SCAA's Minimum Certification Requirements for Coffee Brewers (download PDF):
- Coffee Volume: The volume of the brew basket must be sized in proportion to the beverage receiver's maximum capacity as stipulated by the manufacturer. Minimum technical requirement is for brew basket capacity to accommodate the Golden Cup Ratio weight of coffee per maximum capacity (~55 grams per liter) without overflowing from the basket due to the swelling of the coffee grounds during the brew cycle. This allowance should be about 50% of the bed depth of the coffee. Best results in uniformity of extraction are obtained with coffee bed depths between 2.5 and 5.0 cm, but these dimensions are not a requirement for the certification.
- Brewing Time: The coffee brewer must be able to cycle its full-capacity water volume through the coffee grounds within the prescribed amount of time. For a brewer at maximum coffee and water capacity, the minimum technical requirement is for the water contact time with the coffee grounds shall be more than 4 minutes but less than 8 minutes for all brewers operating under standard temperature and pressure at the manufacturers stated design voltage, depending on grind. Under no circumstances will water contact times in excess of 8 minutes be acceptable in meeting the certification requirements.
- Brewing Temperature: The coffee brewer must be able to cycle the gross water volume through the coffee grounds within the prescribed temperature range. Minimum technical requirement is for the water temperature at the point the water contacts the coffee grounds to reach 92°C within the first minute, maintain at least that temperature (92°C) for the remainder of the brew cycle, and never exceed 96°C. Measurement of brewing temperatures will be made by using an RTD (Resistive Temperature Device) placed at the top and in the center of the bed of coffee in the brew basket.
- Beverage Preparation: The coffee brewer must be able to produce a beverage with the prescribed range of solubles concentration and solubles yield. The brewer will be evaluated at stated full capacity as well as at the 1 liter brew water volume. In situations where 1 liter is the maximum capacity of the brewer, the 0.5 liter brew will also be tested. Testing will begin with a coffee/water ratio of 55g/1L, but will be adjusted depending on the grind and contact time to produce a brew within the Golden Cup zone of the brewing control chart. Minimum technical requirement is for a beverage strength (solubles concentration) of between 1.15% and 1.35% resulting from an extraction (solubles yield) of between 18.0% and 22.0% from the weight of coffee in the brew basket, as determined by a coffee refractometer and brewing control chart. All samples measured on the coffee refractometer are filtered prior to measurement. The grind of the coffee will be adjusted for the water contact time of the brewer in order to achieve these results whenever possible, within the specified grind parameters (see below testing procedures). Brewers must be able to meet these requirements at both full capacity and a 1 liter capacity in order to be certified by the SCAA. Brewers with the full capacity of 1 L will also be tested at 0.5 L.